EFFECT OF CORN PARTICLE SIZE MILLING ON BROILER, PULLET ...

The Pennsylvania State University

The Graduate School

College of Agricultural Sciences

EFFECT OF CORN PARTICLE SIZE MILLING ON BROILER, PULLET, AND LAYER

GROWTH, PERFORMANCE, AND DIGESTIBILITY

A Thesis in

Animal Science

by

Lisa Dorene Kitto

2017 Lisa Dorene Kitto

Submitted in Partial Fulfillment

of the Requirements

for the Degree of

Master of Science

December 2017

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The thesis of Lisa Dorene Kitto was reviewed and approved* by the following:

Paul H. Patterson

Professor of Poultry Science

Thesis Co-Advisor

R. Michael Hulet

Emeritus Associate Professor of Poultry Science

Thesis Co-Advisor

Alan L. Johnson

Walther H. Ott Professor in Avian Biology

Gregory W. Roth

Professor of Agronomy

Terry D. Etherton

Distinguished Professor of Animal Nutrition

Head of the Department of Animal Science

*Signatures are on file in the Graduate School

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ABSTRACT

Corn particle size (PS) is a relatively unexplored topic regarding its impact on

commercial poultry performance grown for meat or eggs. Additionally, there are potential feed

fabrication aspects to consider as mills could potentially save machine energy, wear, and money

by modifying PS. The objectives of the following studies were to: 1) assess hammer mill energy

usage and economic efficiency grinding corn to different geometric mean diameters (GMD), 2)

evaluate the nutrient digestibility, growth performance, and carcass characteristics of broiler

chickens fed treatment GMD corn, and 3) evaluate the growth and performance of pullets and

subsequent productivity and egg quality of laying hens fed corn GMD treatments. Cooperator

feed mill Wenger Feeds, LLC (Rheems, PA) delivered two batches of corn ground to 600, 900,

1200, and 1500 µm by hammer mill. Energy and machine efficiency show larger PS (1200 and

1500 µm) lend themselves to greater efficiency, tonnes per hour (TPH) throughput, and lower

cost/tonne than 600 and 900 µm. Four live bird studies followed: First, a broiler digestibility

study was conducted where apparent ileal digestibility (AID) and true ileal digestibility (TID),

which are ways to measure the ability of amino acids to be absorbed into the bloodstream through

the gastrointestinal tract, and were measured to determine level of nutrient absorption through the

small intestine of 35 day old male broilers. Second, a broiler floor pen study at commercial bird

density was performed with crumbled and pelleted diets. Birds fed the 600 and 900 µm corn diets

showed increased body weight (BW) and body weight gain (BWG) but no significant differences

between treatments for feed intake (FI) or feed conversion ratio (FC). In a third study,

commercial egg laying pullet chicks fed the 600 µm corn through to maturity had consistently

heavier BW than those of other PS treatments. Lastly, from 19 – 43 weeks of age, hens in

conventional cages were fed corn based treatment diets formulated in a phase fed program, with

diets consisting of 50-60% ground treatment corn. Throughout the hen study there were no

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significant differences with the exception of yolk color, which was measured using a Roche yolk

color fan and is tied to consumer preference. It was found the 600 µm treatment yolks were

reduced compared to the 900, 1200, and 1500 µm treatments at 35, 43 weeks of age, and overall.

Body weight (BW), FI, day at first egg, and the number of preovulatory follicles, those follicles

in the rapid growth phase before selection, remained unchanged throughout the hen study,

indicating corn particle size has little to no effect on hen BW, nutrient utilization for follicular

recruitment, egg production, or quality of commercial hens.

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TABLE OF CONTENTS

LIST OF FIGURES ................................................................................................................. viii

LIST OF TABLES ................................................................................................................... ix

ABBREVIATIONS ................................................................................................................. xii

ACKNOWLEDGEMENTS ..................................................................................................... xiii

Chapter 1 INTRODUCTION ................................................................................................... 1

RATIONALE ................................................................................................................... 1 HYPOTHESIS ................................................................................................................. 2 OBJECTIVES .................................................................................................................. 2 REFERENCES................................................................................................................. 4

Chapter 2 LITERATURE REVIEW ........................................................................................ 5

Corn Carbohydrate Metabolism ....................................................................................... 5 Mill Performance ............................................................................................................. 6

Hammer Mill vs. Roller Mill Performance .............................................................. 6 Machinery Energy Usage ......................................................................................... 8 The Pelleting Process ............................................................................................... 8

Bird Live Performance ..................................................................................................... 9 Broilers ..................................................................................................................... 10 Pullets and Layers .................................................................................................... 11 Other Species and Nutrients ..................................................................................... 13 Live Production and Mill Mechanic Synchronicity ................................................. 14

REFERENCES................................................................................................................. 15

Chapter 3 CORN PARTICLE SIZE SEPARATION AND HAMMER MILL

PERFORMANCE ............................................................................................................ 19

ABSTRACT ..................................................................................................................... 19 INTRODUCTION ........................................................................................................... 20 MATERIALS AND METHODS ..................................................................................... 21

Corn Milling and Economics ................................................................................... 21 Sieving and Calculations .......................................................................................... 22 Statistical Analysis ................................................................................................... 23 Nutrient Analysis...................................................................................................... 23

RESULTS AND DISCUSSION ...................................................................................... 24 ACKNOWLEDGEMENTS ............................................................................................. 27 REFERENCES................................................................................................................. 27

Chapter 4 EFFECT OF CORN PARTICLE SIZE ON APPARENT AND TRUE ILEAL

DIGESTABILITY AND JEJUNUM VISCOSITY OF 35-DAY OLD MALE

BROILERS ...................................................................................................................... 38

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Birds and Housing .................................................................................................... 40 Treatment Diet Formulation for the Digestibility Assay .......................................... 41 Digestibility Assay ................................................................................................... 41 Viscosity Assay ........................................................................................................ 42 Nutrient Analysis of Digesta and Complete Treatment Diets .................................. 42 Calculations .............................................................................................................. 43 Statistical Analysis ................................................................................................... 44

RESULTS AND DISCUSSION ...................................................................................... 45 ACKNOWLEDEMENTS ................................................................................................ 49 REFERENCES................................................................................................................. 49

Chapter 5 CORN PARTICLE SIZE EFFECTS IN PELLETED AND CRUMBLED

DIETS ON BROILER GROWTH PERFORMANCE AND CARCASS

CHARACTERISTICS ..................................................................................................... 63


Birds and Housing .................................................................................................... 66 Statistical Analysis ................................................................................................... 67


Chapter 6 EFFECTS OF CORN PARTICLE SIZE ON PULLET GROWTH

PERFORMANCE AND REPRODUCTIVE TRACT DEVELOPMENT ....................... 88


Birds and Housing .................................................................................................... 90 Body Weight, Growth Performance, and Organ Measurements .............................. 91 Statistical Analysis ................................................................................................... 92


Chapter 7 EFFECT OF CORN PARTICLE SIZE ON HEN PERFORMANCE, EGG

QUALITY AND ECONOMICS ...................................................................................... 102


Birds and Housing .................................................................................................... 105 Treatment Diet Formulation ..................................................................................... 105 Data Collection ......................................................................................................... 106

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Body Weight and Production Data ........................................................................... 106 Egg Production & Quality Parameters ..................................................................... 106 Gastrointestinal Tract Measurements and Preovulatory Follicle Determination ..... 107 Statistical Analysis ................................................................................................... 108


Chapter 8 CONCLUSIONS AND FUTURE WORK .............................................................. 125

APPENDIX A

Chapter 6 Summary Tables .............................................................................................. 128

APPENDIX B

Chapter 7 Summary Tables .............................................................................................. 132

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LIST OF FIGURES

Figure 3-1. Corn particle sieving percent separation: 600µm Delivery 1 vs. Delivery 2 ........ 32

Figure 3-2. Corn particle sieving percent separation: 900µm Delivery 1 vs. Delivery 2 ........ 33

Figure 3-3. Corn particle sieving percent separation: 1200µm Delivery 1 vs. Delivery 2 ...... 34

Figure 3-4. Corn particle sieving percent separation: 1500µm Delivery 1 vs. Delivery 2 ...... 35

Figure 4-1. Apparent ileal AA digestibility (%, DM basis) ..................................................... 57

Figure 4-2. True ileal AA digestibility (%, DM basis) ............................................................ 59

Figure 4-3. True ileal AA digestibility with literature EAAL values (%, DM basis) .............. 61

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LIST OF TABLES

Table 3-1. Hammermill economic cost (average amperage, power, TPH, efficiency,

cost/tonne & hr/tonne) ..................................................................................................... 29

Table 3-2. Corn particle size distribution: Percent separation (%) Delivery 11,2

.................... 30


.................... 31

Table 3-4. Corn treatment particle size sieving: GMD and GSD1,2

........................................ 36

Table 3-5. Nutrient composition of corn (“as is” basis)1 ......................................................... 37

Table 4-1. Nutrient composition of experimental diets for digestibility (“as is” basis) .......... 53

Table 4-2. Mean body weight (BW, kg/bird) and body weight gain (BWG, kg/bd) 1,2

........... 54

Table 4-3. Mean ileal endogenous amino acid losses (g/100 g DM) collected from the

terminal end of the ileum1,2

.............................................................................................. 55

Table 4-4. Apparent ileal AA digestibility (%)1 ...................................................................... 56

Table 4-5. True ileal AA digestibility (%)1 ............................................................................. 58

Table 4-6. True AA ileal digestibility (%) from literature EAAL values1 .............................. 60

Table 4-7. Jejunum digesta viscosity of male broilers at 35 days (cP)1,2

................................ 62

Table 5-1. Proximate analysis of completed broiler feed (%)1................................................ 73

Table 5-2. Floor-pen broiler body weight (BW, kg/bd) .......................................................... 74

Table 5-3. Floor-pen broiler body weight gain (BWG, kg/bd) ............................................... 75

Table 5-4. Floor-pen broiler feed intake (FI, kg feed/bd) ....................................................... 76

Table 5-5. Floor-pen broiler feed conversion (FC, kg feed/kg BWG) .................................... 77

Table 5-6. Floor-pen broiler percent mortality and culls (%)1 ................................................ 78

Table 5-7. Floor-pen broiler female mean processing weights (g)1 ........................................ 79

Table 5-8. Floor-pen broiler female mean processing weights as a percent of carcass

weight at 42d1,2

(%) .......................................................................................................... 80

Table 5-9. Floor-pen broiler male mean processing weights (g)1 ........................................... 81

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Table 5-10. Floor-pen broiler male mean processing weights as a percent of carcass

weight at 42d (%)1,2

.......................................................................................................... 82

Table 5-11. Floor-pen broiler combined male and female mean processing weights (g)1 ...... 83

Table 5-12. Floor-pen broiler combined male and female mean processing weights as a

percent of carcass weight at 42d (%)1,2

............................................................................ 84

Table 5-13. Floor-pen broiler female organ weights (g) and lengths (cm)1,2

.......................... 85

Table 5-14. Floor-pen broiler male organ weights (g) and lengths (cm)1,2

............................. 86

Table 5-15. Floor-pen broiler combined organ weights (g) and lengths (cm)1,2

..................... 87

Table 6-1. Pullet body weight (BW, g/bird) and body weight gain (BWG, g/bird) 1,2

............ 98

Table 6-2. Pullet feed intake (FI, g/bird/day)1,2

....................................................................... 99

Table 6-3. Pullet feed conversion (FC, g feed/g gain)1,2

......................................................... 100

Table 6-4. Pullet organ weights and lengths (16 weeks)1 ....................................................... 101

Table 7-1. Mean hen day egg production (%) by dietary treatment1 ...................................... 114

Table 7-2. Mean eggs per period (28d) per hen housed by dietary treatment1 ........................ 115

Table 7-3. Hen body weight (BW, kg) .................................................................................... 116

Table 7-4. Egg weights (g) ...................................................................................................... 117

Table 7-5. Feed intake (g/hen/day)1 ........................................................................................ 118

Table 7-6. Feed conversion (kg feed/dozen eggs)1 ................................................................. 119

Table 7-7. Feed conversion (kg feed/kg eggs)1 ....................................................................... 120

Table 7-8. Egg quality ............................................................................................................. 121

Table 7-9. Pullet organ weights and lengths (19 weeks)1 ....................................................... 122

Table 7-10. Hen organ weights and lengths (31 weeks)1 ........................................................ 123

Table 7-11. Hen organ weights as a percent of BW (%) (31 weeks)

1,2 ................................... 124

Appendix A.1. Pullet starter diets ........................................................................................... 128

Appendix A.2. Pullet grower diets .......................................................................................... 129

Appendix A.3. Pullet developer diets ..................................................................................... 130

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Appendix A.4. Pullet pre-lay diets .......................................................................................... 131

Appendix B.1. Hen diets phase 1, periods 1 & 2 .................................................................... 132



Appendix B.4. Egg proportions (g) ......................................................................................... 135

Appendix B.5. Hen organ weights and lengths (43 weeks)1 ................................................... 136

Appendix B.6. Hen organ weight as a percent of body weight (%) (43 weeks)1,2

.................. 137

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ABBREVIATIONS

µm = Microns

AA = Amino acid

AAdiet = Amino acid concentration in diet

AAdigesta = Amino acid concentration in ileal digesta

AIAdiet = Acid insoluble ash concentration in diet

AIAdigesta = Acid insoluble ash concentration in ileal digesta

AID = Apparent ileal amino acid digestibility

BW = Body weight

BWG = Body weight gain

CF = Crude fiber

CP = Crude protein

cP = Centipoises

Delivery 1 = Ground corn delivered February 2016

Delivery 2 = Ground corn delivered October 2016

DM = Dry matter

EAAL = Endogenous amino acid loss concentration (current study)

EAALLit = Endogenous amino acid loss concentration (Lemme et al. 2004)

EE = Ether extract

EHC = Enzymatically hydrolyzed casein

ESCL = University of Missouri Agricultural Experiment Station Chemical Lab

FC = Feed conversion ratio

FI = Feed intake

g = Grams

GMD = Geometric mean diameter (µm)

GSD = Geometric standard deviation (µm)

IACUC = Institutional animal care and use committee

kg = Kilograms

KW = Kilowatts

KWh = Kilowatt hours

ME = Metabolizable energy

PDI = Pellet durability index

PF = Protein-free diet

PS = Particle size

RPM = Revolutions per minute

SEM = Pooled standard error of the means

TID = True ileal amino acid digestibility

TIDLit = True ileal amino acid digestibility using EAALLit

TPH = Throughput (tonnes/hour)

V = Volts

VFD = Variable frequency drive

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ACKNOWLEDGEMENTS

These studies were funded through the 2015 Pennsylvania Poultry Industry Egg and

Broiler Research Check-Off Programs.

Special thanks to my advisors Dr. Paul Patterson and Dr. Michael Hulet for their

guidance, understanding, and support through my time at Penn State. I am so thankful for

everything they have taught me over my time here and wouldn’t trade those lessons for the world.

Thanks also to my committee members Dr. Alan Johnson and Dr. Greg Roth for imparting their

knowledge and valuable advice on me through my studies.

I also wish to thank Dr. Jude Liu, Dr. Virendra Puri, Dr. Hojaye Yi, Jill Hadley, and Kate

Anthony for all their help and assistance in completing my projects. I’d like to sincerely thank

everyone at The Penn State Poultry Education Research Center (Scott Kephart, Tim Price, Dave

Witherite, and Ben Kunkel) for their hard work and willingness to help with these projects.

Thank you to Wenger Feeds, LLC, specifically Chris Olinger, Doug Goodling, and Larry

Hammaker for cooperating with us on these projects, including manufacturing all of the treatment

corn particle sizes, delivery of corn, and broiler feed for all projects. Your aid has been

invaluable.

Finally, thank you to my friends, especially Amy Barkley and Erica Rogers for their

research support and friendship – I never could have completed everything without their help.

Thank you to my parents, Leslie and George, for always pushing me to reach my goals, and

reminding me to never let anything get in the way of those goals. Evrard, my love, thank you so

much for the constant support, love, and steady supply of dark chocolate through my studies, I

can never thank you enough for everything you have done and continue to do for me every single

day.

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Chapter 1 INTRODUCTION

RATIONALE

In the poultry industry, feed ingredient costs have risen considerably in the past 10 years,

accounting for nearly 70% of all live production costs (Donohue and Cunningham, 2009). With

the average US poultry diet containing 60% corn (Leeson and Summers, 2005), final

determination of an optimum corn particle size (PS) for the poultry industry (broilers, pullets, and

layers, specifically) is of greater importance now more than ever.

Despite work having been done in this particular field, results are contradictory and the

live production studies may have confounding factors. For example, previous work has shown no

differences in percent separation between PS treatments after the pelleting process (Engberg et

al., 2002; Amerah et al., 2008), while other studies have noted differences in particle separation

have remained pre- and post-pelleting (Péron et al., 2005) when utilizing ground wheat in pelleted

broiler diets. Along with feed form, other parameters influence optimum PS, such as pelleting

method, grain type, and grinding method (Amerah et al., 2007). While more finely ground

ingredients have been thought to produce pellets with a higher pellet durability index (PDI), corn

flowability through bins and chutes of a feed mill may be impaired such that the mechanical

energy cost and loss of flowability are too great for a feed mill to sustain.

Bird live performance also must be evaluated, as previous work has shown birds’

preference for larger particle size increases as they age and their mouth gape increases (Nir et al.,

1994b). Additionally, it has been determined that birds prefer more uniform feed particles when

in a mash form, and the more uniform a feed is, the less time a bird will spend looking for and

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ultimately choosing larger particles (Nir et al., 1994a).

Ultimately, weighing the benefits and costs of the wide range of commonly used corn

particle sizes utilized in the commercial poultry industry may lead to a greater understanding of

which corn PS is most appropriate for a given type of bird at a specific age and perhaps realize

cost savings benefits for both bird live performance and for feed mills.

HYPOTHESIS

Particle size will affect broiler and pullet nutrient digestibility and growth performance,

as well as hen performance, measured by egg production, and optimization of corn particle size

can contribute to cost-savings for feed mills for all commercial poultry.

OBJECTIVES

1. To assess milling energy usage, economic efficiency and particle size distribution of

corn ground for different geometric mean diameters.

2. To evaluate broiler chicken nutrient absorption and live performance.

a. To measure the apparent and true digestibility of four treatment corn particle

sizes (600, 900, 1200, and 1500 µm).

b. To measure the jejunum digesta viscosity of the four treatment corn particle

sizes.

c. To assess the impact of corn particle size on broiler live performance

(growth, feed intake, feed conversion, carcass characteristics) and

gastrointestinal organ measurements.

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3. To evaluate the impact of corn particle size on the growth of pullets and their

subsequent productivity and egg quality as laying hens.

a. To establish if there is an impact of corn particle size (600, 900, 1200, and

1500 µm) on pullet growth and reproductive performance, including body

weight, body weight gain, feed intake and feed conversion.

b. To assess the impact of corn particle size (600, 900, 1200, and 1500 µm) on

laying hen performance, including percent production, feed conversion (kg

feed/ kg egg and kg feed/ dozen eggs), body weight, and mean eggs per hen

in a 28 d period.

c. Finally, to establish which corn particle size has the most positive economic

impact on egg quality and egg proportions in terms of albumen height,

accompanying Haugh units, yolk color, and egg proportions.

4

REFERENCES

Amerah, A. M., V. Ravindran, R. G. Lentle, and D. G. Thomas. 2007. Feed particle size:

Implications on the digestion and performance of poultry. Worlds. Poult. Sci. J. 63:439–

455.

Amerah, A. M., V. Ravindran, R. G. Lentle, and D. G. Thomas. 2008. Influence of feed particle

size on the performance, energy utilization, digestive tract development, and digesta

parameters of broiler starters fed wheat- and corn-based diets. Poult. Sci. 87:2320–2328.

Donohue, M., and D. L. Cunningham. 2009. Effects of grain and oilseed prices on the costs of US

poultry production. J. Appl. Poult. Res. 18:325–337.

Engberg, R. M., M. S. Hedemann, and B. B. Jensen. 2002. The influence of grinding and

pelleting of feed on the microbial composition and activity in the digestive tract of broiler

chickens. Br. Poult. Sci. 43:569–579.

Leeson, S., and J. D. Summers. 2005. Commercial Poultry Nutrition. 3rd Ed. Context Products

Ltd., Packington, Leicestershire England.

Nir, I., R. Hillel, G. Shefet, and Z. Nitsan. 1994a. Effect of grain particle size on performance: 2.

Grain texture interactions. Poult. Sci. 73:781–791.

Nir, I., G. Shefet, and Y. Aaroni. 1994b. Effect of particle size on performance: 1. Corn. Poult.

Sci. 73:45–49.

Péron, A., D. Bastianelli, F. X. Oury, J. Gomez, and B. Carré. 2005. Effects of food deprivation

and particle size of ground wheat on digestibility of food components in broilers fed on a

pelleted diet. Br. Poult. Sci. 46:223–230.

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Chapter 2 LITERATURE REVIEW

Corn Carbohydrate Metabolism

Corn has become the worldwide standard cereal grain in poultry feed to which all high

energy yielding ingredients are compared. Historically, nearly 75% of all corn produced in the

United States has been used for animal feed (Tollenaar and Dwyer, 1999), and feed ingredients

are still considered to be the most costly component of poultry production, at nearly 69% of all

live production cost in 2008 (Donohue and Cunningham, 2009). Furthermore, corn accounts for

approximately 60% of a standard commercial US poultry diet (Leeson and Summers, 1984). Corn

is widely used because of the high starch content in the endosperm, which accounts for 83% of

total kernel (Tollenaar and Dwyer, 1999). Between 2002 and 2008, corn utilized for ethanol

production in the United States increased from 11% to 30% of the total available corn crop in the

country (Donohue and Cunningham, 2009).

Starch is part of the large class of macronutrients called carbohydrates, which also

include sugars and cellulose. The simplest of carbohydrates that a bird can readily use in

metabolic processes are called monosaccharides, such as glucose. Starch is easily broken down in

the gastrointestinal tract, beginning in the mouth and crop with the salivary enzyme amylase.

Once in the chicken’s proventriculus, hydrochloric acid, pepsin, and other digestive enzymes are

secreted, beginning chemical carbohydrate breakdown. Manual breakdown of feed particles

occurs once it moves into the gizzard, where strong muscles mash feed and digestive enzymes

from the proventriculus, facilitate mechanical and chemical breakdown. The small intestine can

be segregated into three sections: the duodenal loop with pancreas and gall bladder, the jejunum

at the distal end of the duodenal loop to Meckel’s diverticulum, and the ileum from Meckel’s

diverticulum to the ileo-cecal junction is the last section of the small intestine. By the time feed

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enters the small intestine, any large chain starch molecules are broken down to single glucose

molecules, which poultry can easily absorb. Approximately 80% of glucose absorption occurs

through active transport in the small intestine, though small amounts of carbohydrate absorption

occur in the cecum (Denbow, 2000).

Mill Performance

While corn has been the standard energy-yielding feed ingredient in the United States for

poultry, little attention has been paid to the milling aspects of corn particle size (PS). As corn is

generally brought to feed mills whole, corn endosperm hardness and percent moisture are corn

factors which can affect PS reduction, and while no hard and fast rules exist for types of

machinery to reduce PS, two common types of equipment; the hammer mill and the roller mill

may be used. Historically, individual mill settings varied for “coarse”, “medium”, and “fine”

grinds. Currently, most mills now utilize a standard set of screens and a sieve shaker, such as that

described in ASABE Standard S319.4 (2008). This standardization allows PS determination

across feed mills in terms final geometric mean diameter (GMD) and geometric standard

deviation (GSD) rather than “coarse”, “medium”, or “fine” terminology.

Hammer Mill vs. Roller Mill Performance

The primary goal of PS reduction for corn is to physically break it down, exposing the

interior endosperm layers and increasing the surface area which aids digestive enzyme action.

The hammer mill, which is utilized more frequently in industry settings, utilizes fast moving

hammers to break the corn to fit though a chosen screen size (Koch, 2002). These screens can be

changed out as needed by the feed mill based on their PS goal. Particles created using a hammer

7

mill tend to be spherical in shape but tend to have a higher geometric standard deviation (GSD).

Roller mills press corn between multiple sets of horizontal rollers with constant pressure on each

set of rollers. Unlike hammer mills, roller mills tend to produce particles which result in a small

GSD, are more energy efficient, but have increased maintenance costs compared to hammer mills

(Koch, 2002). Roller mills have been found to have greater energy savings for coarse ground

particles (over 1,000 µm) compared to the hammer mill, but as PS decreases, the savings become

minimal (Behnke, 1996). Previous work has been done comparing hammer mill and roller mill

ground corn for bird live performance. Reece et al., (1985) concluded that corn ground using a

roller mill to a GMD of 1,343 µm or using a hammer mill to 814 µm and then made into

crumbled feed, found broilers fed the roller mill corn to have performed equally to those birds fed

the hammer mill ground corn when grown to 47 days of age.

Cereal grain type can also impact final PS, GMD, and GSD. Milanovic (2017) reported

cereal grains which are more fibrous (barley or oats) are less efficiently ground than more brittle

cereal grains, such as corn or wheat. Corn and wheat ground using a hammer mill with either a 1-

or 7-mm screen (fine or coarse ground, respectively) found corn had a GMD of 297 µm or 528

µm, respectively, and wheat was 284 µm or 890 µm GMD, respectively (Amerah et al., 2007,

2008), indicating cereal grain types will behave differently due to inherent properties of each

grain type. Cereal grains with high moisture content have been found to increase energy

consumption of both hammer and roller mills (Milanovic, 2017) and ingredient is the second

most expensive operation in the feed manufacturing process after pelleting according to Reece et

al. (1985).

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Machinery Energy Usage

The cost of feed production, including equipment, energy, maintenance, as well as labor,

land, building and feed ingredient procurement are related to the economic return for all types of

poultry production (CPM, 2017). While the hammer mill is more commonly used in commercial

practice, it can also be more expensive to run due to greater its electrical usage compared to roller

mill usage. Type of mill used to grind corn can also affect overall energy costs. For example, a

roller mill and hammer mill both set to grind 29,000 tonnes of corn yearly to a GMD of 600 µm

would cost a feed mill operating a hammer mill $14,000 and a roller mill $8,000 in electrical

costs, resulting in a cost savings of $6,000 yearly (CPM, 2017). The electrical costs of a hammer

mill grinding 29,000 tonnes of corn per year to either 1200 µm or 600 µm, is approximately

$3,000 and $14,000, respectively (CPM, 2017). Interestingly, screen size of hammer mills also

affects energy usage and grain reduction as large screen openings result in less particles colliding

with the hammers and screen, reducing energy consumption as a result of PS reduction (Martin,

1985). Finer grinding of cereal grains decreases throughput (TPH, tonnes/hr) and slows down

feed mill production rates. Greater PS increases mill efficiency with greater grain flowability,

TPH and reduced energy costs that can decrease final feed costs incurred by poultry producers.

The Pelleting Process

Finer corn particles produce more durable, high quality pellets with less fines. The

poultry industry pellets and crumbles broiler feed rather than feed a mash diet because it

significantly increases feed intake (FI), body weight (BW), and body weight gain (BWG)

(Engberg et al., 2002). Desire for a high quality pellet or crumble currently leads the US poultry

industry to grind corn more finely, as it is believed pelleting also removes the bird’s ability to

9

waste time and energy searching and ultimately selecting larger particles as the feed is more

uniform in pelleted and crumbled feed compared to a mash diet (Portella et al., 1988). Reece et al.

(1986a) ground corn to a GMD of 679, 987, or 1,289 µm and subsequently pelleted the diets. The

resulting pellets from the 1,289 µm corn treatment had a significantly higher pellet durability

index (PDI) than the two more finely ground treatments. Another study by Reece et al. (1985)

utilized hammer mill ground corn (814 µm GMD) created using a screen size of 0.48 cm in

diameter, or roller mill ground corn created using one set of rollers with 2 grooves/cm, 0.853 mm

spacing between roller pairs, while the bottom rollers had 5.1 grooves/cm with 0.318 mm spacing

and generated corn at 1,343 µm GMD. The roller mill reduced energy required to grind the corn

by 14.5% compared to a hammer mill. Engberg et al. (2002) and Péron et al. (2005) determined

the pelleting process breaks larger particles between the pellet rollers and the die, effectively

removing differences between PS treatments of wheat (Engberg et al., 2002). Other research has

found that PS can be maintained through the pelleting process (Nir et al., 1995). Their study

examining four treatments of varying PDI, PS and feed form evaluated both high- and low-

quality pellets (88% and 66% PDI, respectively), ground corn (2600 µm GMD) added post-

pelleting (89% PDI), and ground corn (1200 µm GMD) fed as a mash. They determined broilers

fed the mash PS treatment had significantly poorer BWG and meat recovered than all other

treatments and broilers fed high-quality pellets showed higher overall BW and FI than those birds

fed low-quality pellets.

Bird Live Performance

Beak size and gape have been found to influence a bird’s preference for feed PS. Young

chickens are unable to consume larger particles easily, though have been found to prefer larger

particles as they age and their beak increases in size (Morgan and Heywang, 1941; Nir et al.,

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1994b). Birds search for, and ultimately choose larger particles, and the more uniform a diet is,

the less time a bird will spend searching for its meal (Nir et al., 1994a).

Broilers

Efficiency is the primary goal in commercial broiler production, as the greatest

production levels are realized in birds with the greatest body weight (BW) and body weight gain

(BWG) with the lowest feed conversion (FC). Pelleting and crumbling feed is a great part of

better FC as birds are physically able to consume more feed in a more efficient way while still

absorbing and utilizing nutrients as efficiently as a mash diet. By pelleting, particle selection

among broilers is reduced. Previous studies have focused on cereal grain PS in mash diets to

measure differences. Nir et al. (1994b) found corn ground to coarse (2010 µm), medium (897

µm), and fine (525 µm) GMD in diets fed to broilers through 21 days of age had improved BW

and BWG when fed the coarse or medium corn over the finely ground corn in mash form. This

indicates that feed uniformity is of great importance when mash diets are being fed. Nir et al.

(1995) reported PS can be maintained through the pelleting process when utilizing sorghum and

wheat based diets. Reece et al. (1986b) examined broilers fed a crumbled starter and pelleted

grower diets incorporating a fine or medium PS of wheat (300 or 955 µm GMD, respectively) and

subsequently found the treatments had equal growth performance with no negative effects as a

result of greater PS.

Additional work has evaluated the impact of diet ingredient PS on broiler gastrointestinal

tract lengths and weights. Larger, more coarse particles maintain a slower passage rate through

the digestive tract than finer particles, which allows for greater exposure time for digestive

enzymes to work upon the particles, possibly improving nutrient utilization and digestibility

(Carré, 2000). The small intestine is of greatest interest, as the grand majority of nutrient

11

absorption occurs in this part of the gastrointestinal tract. Taylor and Jones (2004) fed broilers

wheat based diets and reported no differences in duodenum weight but significantly greater

duodenum length in birds fed whole wheat compared to birds fed ground and pelleted wheat

diets. Multiple studies (Nir et al., 1995; Engberg et al., 2002) found gizzard weight and small

intestine segment lengths were significantly reduced when birds were fed pelleted or crumbled

diets rather than mash utilizing the same original PS in all treatments. This effect could be due to

varying PS as well as the process of pressing and heating pellets as they’re formed and further

breaking down carbohydrate bonds.

Pullets and Layers

Historical work focusing specifically on ingredient PS in pullets and layer diets is

minimal, though some research suggests that more focus on cereal grain PS in the growth period

of younger pullets could have great impact on BW and BWG between hatch and 16 weeks of age.

Frikha et al. (2011) studied brown egg laying hen pullets fed either corn or wheat (at 50% of their

diet) ground through a 6-, 8-, or 10-mm screen, and found the finely ground corn (929 µm

geometric mean diameter) had significantly better BWG and FC through 6 weeks of age than

greater corn particle sizes measured at 991 µm and 1,042 µm GMD, and all wheat treatments

(967, 1119, 1216 µm). While the studies herein focus solely on Hy-Line W-36 pullets and laying

hens, work by Leeson et al. (1997) considered strains of laying hens in terms of how they choose

and digest protein, as crude protein (CP) availability is also thought to be impacted by grain PS.

Leeson et al. (1997) fed Babcock, DeKalb, H & N, and Shaver pullets either a conventional diet

with 19.5% CP or low CP (16.5%) diet with similar Lys and Met + Cys concentrations and saw

no significant differences between rearing diet treatment by 18 weeks and concluded minor strain

differences exist in the pullet stage of life when considering level of protein in a diet. However,

12

cereal PS in concert with varying CP levels in a pullet diet could alter performance and

reproductive growth in the pullet stage of life. Additionally, pullets which were lighter in BW at

18 weeks of age consumed less feed, reached sexual maturity later, and laid lighter weighted eggs

and less overall egg mass, by 70 weeks of age than a heavier pullet (Leeson et al., 1997).

While potential differences between PS treatments may exist in pullets, previous work

available on laying hens indicates there is little difference in production performance parameters.

Deaton et al. (1988) fed corn ground by roller (1,343 – 1,501 µm) or hammer mill (814 – 873

µm) into laying hen mash diets and found PS range did not influence hen percent egg production,

BW, egg weight, FI, FC (g feed/g egg), or eggshell breaking strength. Morgan and Heywang,

(1941) determined pelleting hen diets can reduce feed wastage, hen energy expenditure and time

spent choosing or eating feed, thus improving nutrient uptake. Hy-Line (2016) recommends

pullets be fed a crumbled starter and later a mash grower diet with 25% of particles less than

1,000 µm, 65% between 1,000 – 2,000 µm and 10% between 2,000 – 3,000 µm. For pullet

developer and laying hen diets they recommend increasing the range to include 35% PS between

1,000 – 2,000 µm and 2,000 – 3,000 µm plus 5% of particles greater than 3,000 µm. These

recommendations suggest a smaller PS is more beneficial for younger, smaller pullets.

More recently, Safaa et al. (2009) ground dent corn or Durum wheat to pass through

either a 6-, 8-, or 10-mm screens on a hammer mill, where the ground corn GMDs ranged from

774, 922, and 1165 µm and ground wheat GMDs ranged from 998, 1,111, 1,250 µm. These corn

and wheat PS were fed to Lohmann Brown hens from 20 to 48 weeks of age, and it was

determined there were no significant differences between grain type, or coarseness of grind, and

all production and egg quality parameters remained unaffected. However, FI increased slightly

with greater PS notwithstanding cereal grain type (107.9, 108.0 vs.110.6 g/bd/d). Similarly,

Hamilton and Proudfoot (1995) fed White Leghorn hens wheat ground to either a fine or coarse

PS in a mash diet (GMD was never defined), and reported hen BW, egg production, weight, and

13

FC were not significantly impacted by PS treatments throughout the study. These studies suggest

hen performance and egg parameters are not influenced by ingredient PS in mash diets.

Other Species and Nutrients

Focusing on calcium source and PS for laying Longyan ducks (Wang et al., 2014)

evaluated limestone and oyster shell at two particle sizes (either < 100 µm or between 850 –

2,000 µm GMD) from 24 – 36 weeks of age, and reported limestone with greater PS was more

efficiently utilized by the ducks and had significantly greater egg production, egg quality, and

bone strength as a result, indicating an effect from the differing particle sizes of the limestone and

oyster shell.

Much like the poultry industry, the swine industry has been interested in cereal grain PS,

its impact on feed costs, live performance, and carcass characteristics. Refining the impact of

ingredient PS is hampered by application of terms like fine, medium, and coarse grinds, making a

clear definition of PS difficult between cereal grains and different mills. Healy et al. (1994) fed

weanling pigs ground corn, hard endosperm sorghum, or soft endosperm sorghum in pelleted

form, though PS definition was left unclear. The authors found piglets fed the corn treatment had

6% better FC and 23% better BWG than pigs fed either sorghum based diets and found PS to be

most influential for the first two weeks of life with the most reduced PS (300 µm) being most

beneficial to piglet growth. Pigs prefer greater PS with increasing age but have been found to

perform better, no matter age, with finer ground feed, even though more finely ground feed has

also been found to produce gastric ulcers. In swine, as fine feed becomes more fluid when

combined with digestive juices than coarse feed, the possibility of ulceration increases greatly as

PS dips below 500 µm (Goodband et al., 2002).

14

Live Production and Mill Mechanic Synchronicity

Reducing feed ingredients to their desired PS is the second most expensive operation in a

mill after the cost of pelleting (Reece et al., 1985) and the greatest cost in all mash layer diets

(Deaton et al., 1988). Finely ground feed has a greater chance to hang up in bulk bins and

conveyance equipment, decreasing flowability, and increasing dustiness (Goodband et al., 2002).

While there may be live performance gains made with finer corn PS, there is also great savings in

more coarsely ground corn, as energy and mechanical cost put forth by the feed mills could

outweigh the benefits seen from finely ground corn included into diets. In addition, reduced

hammer mill energy consumption and increased production rate is realized when grinding whole

grains to a coarser PS. The same theme can be seen in swine production, where pigs fed grain

ground to a GMD 500 µm had a 6% improvement in FC compared to pigs fed 900 µm GMD

ground grain, and tonnes of feed ground/hr was severely reduced by 43% when decreasing PS

from 900 µm to 500 µm (Goodband et al., 2002).

While grinding corn or other cereal grain to a finer PS results in greater energy costs,

lower throughput, as well as an increased feed cost, Reece et al. (1986b) reported increasing

hammer mill screen size from 4.76 mm to 6.35 mm could result in an energy cost saving of 27%.

Martin (1985) determined the fineness of corn ground has no effect on rate or energy consumed

during the pelleting process. While broilers and pullets are still in growing phases of life, a more

finely ground PS with greater BW or BWG later in life, once bones and organs are fully grown,

finer cereal PS may be unnecessary for improved live bird performance and does not outweigh

feed manufacturing costs.

15

REFERENCES



455.




ASABE. 2008. Method of determining and expressing fineness of feed materials by sieving:

American Society of Agricultural and Biological Engineers S319.4 Feb 2009 (Rev. 2012).

American Society of Agricultural and Biological Engineers, St. Joseph, MI.

Behnke, K. C. 1996. Feed manufacturing technology: Current issues and challenges. Anim. Feed

Sci. Technol. 62:49–57.

CPM. 2017. Economics of grinding for pelleted feeds. California Pellet Mill. Available at

http://www.cpm.net/downloads/Economics of Grinding for Pelleted Feeds.pdf (verified 1

July 2017).

Carré, B. 2000. Effets de la taille des particules alimentaires sur les processus digestifs chez les

oiseaux d’élevage. INRA Prod. Anim. 13:131–136.

Carré, B., N. Muley, J. Gomez, F.-X. Oury, E. Laffitte, D. Guillou, and C. Signoret. 2005. Soft

wheat instead of hard wheat in pelleted diets results in high starch digestibility in broiler


Deaton, J. W., B. D. Lott, and J. D. Simmons. 1988. Hammer mill versus roller mill grinding of

corn for commercial egg layers. Poult. Sci. 1:1342–1344.

Denbow, D. M. 2000. Gastrointestinal Anatomy and Physiology. Pages 299–325 in Sturkie’s

Avian Physiology. Fifth Ed. Academic Press, Cambridge, MA.

16






Frikha, M., H. M. Safaa, M. P. Serrano, E. Jiménez-Moreno, R. Lázaro, and G. G. Mateos. 2011.

Influence of the main cereal in the diet and particle size of the cereal on productive

performance and digestive traits of brown-egg laying pullets. Anim. Feed. Sci. Tech.

164:106–115.

Goodband, R. D., M. D. Tokach, and J. L. Nelssen. 2002. The effects of diet particle size on

animal performance. Kansas State Univ. Agricultural Experiment Station and Cooperative

Extension Service, Manhattan, KS. MF-2050:1-6.

Hamilton, R. M. G., and F. G. Proudfoot. 1995. Effects of ingredient particle size and feed form

on the performance of Leghorn hens. Can. J. Anim. Sci. 75:109–114.

Healy, B. J., J. D. Hancock, G. A. Kennedy, P. J. Bramel-Cox, K. C. Behnke, and R. H. Hines.

1994. Optimum particle size of corn and hard and soft sorghum for nursery pigs. J. Anim.

Sci. 72:2227–2236.

Hy-Line. 2016. Hy-Line W-36 Commercial Layer Management Guide 2016. Available at

http://www.hyline.com/UserDocs/Pages/36_COM_ENG.pdf (verified 7 January 2016).

Koch, K. 2002. Hammer mills and roller mills. Kansas State Univ. Agricultural Experiment

Station and Cooperative Extension Service, Manhattan, KS. MF-2048:1-5.

Leeson, S., L. Caston, and J. D. Summers. 1997. Layer performance of four strains of Leghorn

pullets subjected to various rearing programs. Poult. Sci. 76:1–5.

Leeson, S., and J. D. Summers. 1984. Influence of nutritional modification on skeletal size of

Leghorn and broiler breeder pullets. Poult. Sci. 63:1222–1228.

17

Martin, S. A. 1985. Comparison of hammer mill and roller mill grinding and the effect of grain

particle size on mixing and pelleting. MS Thesis. Kansas State Univ., Manhattan, KS.

Milanovic, S. 2017. Literature review on the influence of milling and pelleting on granulation and

physical characteristics, and production cost of pelleted poultry feed. MS Thesis. Norwegian

University of Life Sciences, Postboks 5005, Norway.

Morgan, R., and B. Heywang. 1941. A comparison of a pelleted and unpelleted all-mash diet for

laying chickens. Poult. Sci. 20:62–65.

Nir, I., R. Hillel, I. Ptichi, and G. Shefet. 1995. Effect of particle size on performance. 3. Grinding

pelleting interactions. Poult. Sci. 74:771–783.




Sci. 73:45–49.




Portella, F. J., L. J. Caston, and S. Leeson. 1988. Apparent feed particle size preference by

broilers. Can. J. Anim. Sci. 68:923–930.

Reece, F. N., B. D. Lott, and J. W. Deaton. 1985. The effects of feed form, grinding method,

energy level, and gender on broiler performance in a moderate (21 C) environment. Poult.

Sci. 64:1834–1839.

Reece, F. N., B. D. Lott, and J. W. Deaton. 1986a. The effects of hammer mill screen size on

ground corn particle size, pellet durability, and broiler performance. Poult. Sci. 65:1257–

1261.

Reece, F. N., B. D. Lott, and J. W. Deaton. 1986b. Effects of environmental temperature and corn

particle size on response of broilers to pelleted feed. 65:636–641.

18

Safaa, H. M., E. Jimenez-Moreno, D. G. Valencia, M. Frikha, M. P. Serrano, and G. G. Mateos.

2009. Effect of main cereal of the diet and particle size of the cereal on productive

performance and egg quality of brown egg-laying hens in early phase of production. Poult.

Sci. 88:608–614.

Taylor, R. D., and G. P. D. Jones. 2004. The incorporation of whole grain into pelleted broiler

chicken diets. II. Gastrointestinal and digesta characteristics. Br. Poult. Sci. 45:237–246.

Tollenaar, M., and L. M. Dwyer. 1999. Physiology of Maize. Pages 169–199 in Crop Yield:

Physiology and Processes. Smith, D.L., Hamel, C., eds. 1st Ed. Springer, Berlin, Germany.

Wang, S., W. Chen, H. X. Zhang, D. Ruan, and Y. C. Lin. 2014. Influence of particle size and

calcium source on production performance, egg quality, and bone parameters in laying

ducks. Poult. Sci. 93:2560–2566.

19

Chapter 3 CORN PARTICLE SIZE SEPARATION AND HAMMER MILL

PERFORMANCE

ABSTRACT

Ground corn of different geometric mean diameters (GMD) was utilized for a mash fed

broiler digestibility study, a crumbled and pelleted floor pen broiler study, a mash fed pullet and

subsequent hen study. Corn particle size (PS) treatments (600, 900, 1200, or 1500 µm) were

ground and delivered in totes at one of two different intervals (Delivery 1 and Delivery 2) and

analyzed for nutrients in triplicate and PS distribution in percentage using the ASABE procedure

S319.4 to calculate the GMD and geometric standard deviation (GSD). Energy expenditures from

the feed mill (Wenger Feeds, LLC, Rheems, PA) were analyzed for electrical usage put forth

from the hammer mills used to grind the corn to each given PS treatment. Measurements included

power, amperage of the motors using during grinding, rate at which corn was ground in tonnes/hr

(TPH), efficiency, cost ($/tonne and $/KWhr), and speed of (hr/tonne) grinding. Economic

analysis showed a linear trend with reduced energy cost and higher TPH with greater PS. The

GMD was found to fall within 250 µm of the goal PS for all treatments and both deliveries and

GSD was decreased for Delivery 2 compared to Delivery 1 (0.30-0.38 vs. 0.400-0.47). Based on

the results of energy usage, TPH, rate, and consistency, feed mills would benefit from a larger

grind of corn in poultry diets whenever possible. Further exploration into the effects of varying

corn PS on poultry performance will follow.

20

INTRODUCTION

Soybean meal is utilized as the predominant protein ingredient in the United States,

however, because it is pre-processed before entering the mill, feed mills have little control over

its PS. However, feed mills have greater control over energy ingredients such as maize, wheat,

barley and other cereal grains. These can be ground at the feed mill and vary based on the PS goal

of the mill. By identifying an optimum corn PS for a given sector of poultry production, there is

an opportunity to maximize feed efficiency and nutrient absorption for broilers, pullets, and

layers (CPM, 2017).

Two types of equipment are commonly used to reduce PS; hammer mill and roller mill.

Generally, the hammer mill is used more frequently because of lower maintenance costs and a

simpler user interface. Hammer mills consist of flailing metal rods, swinging in a chamber

forcing the grains into and thorough a screen of a given size. On the other hand, roller mills have

one or more sets of horizontal rollers with the distance between rollers adjusted to arrive at the

desired PS. Due to constant pressure between the rollers, grain size tends to be more uniform

(Amerah et al., 2008). The fineness of dietary cereal grain PS plays a large role in pellet quality

and bird performance. Poor pellet quality resulting from improper PS cereals decreases the

benefits broilers receive from the pelleting process. Additionally, different cereal grains have

unique PS that is achieved with a given screen size (Amerah et al., 2007), indicating that even

with a specific PS goal, mills likely will need to adjust their roller or hammer mills when using

different cereal grains for accurate PS realization.

Broiler and layers alike have been shown to have a preference for greater PS as the bird

grows with age (Portella et al., 1988). Furthermore, PS has been shown to be more important

when in mash diets rather than as crumbles or pellets (Nir et al., 1995; Péron et al., 2005), but

there is also the question as to whether the PS is further reduced during the pelleting process as

21

there are conflicting reports regarding this process. One study by Péron et al. (2005), showed the

distribution of particles between differing grinds of wheat remained consistent both before and

after pelleting, while other studies (Engberg et al., 2002; Amerah et al., 2008) reported pelleting

nullified the effects of the original particle sizes between treatments of ground wheat. When

Amerah et al. (2008) compared wheat and corn, ground to both fine and coarse PS (297 and 528

µm, respectively), then pelleted and fed to male broilers through 21 days of age, the results still

revealed PS distribution differences after pelleting. The coarse grinding of the pelleted corn diet

improved BWG compared to the finely ground, pelleted corn diet (Amerah et al., 2008). These

results would suggest there’s an opportunity to target corn PS for a specific age, type of bird, and

form of feed to optimize bird performance. Work on PS in other species has shown similar

results. Healy et al. (1994) found weanling pigs had greater need for a finer particle size during

the first two weeks post-weaning then PS increases with age. Milling energy utilized will be

greatly affected by the PS goal, thereby allowing a potential cost savings in milling and poultry

feed fabrication.

MATERIALS AND METHODS

Corn Milling and Economics

Wenger Feeds, LLC (Rheems, PA) ground whole corn into four treatment PS (600, 900,

1200, and 1500 µm) at their Muncy, PA mill in two deliveries (Delivery 1 was received at Penn

State’s Poultry Education Research Center in February 2016, Delivery 2 was received in October

2016). Both Delivery 1 and Delivery 2 were ground using two hammer mills (both Sprout, model

#3818), one fitted with a 96.52 cm diameter coarse grind screen hole, and the other with a 45.72

cm diameter screen hole for the medium grind. The medium grind hammer mill was used to grind

22

the 600 µm and 900 µm, with a 150-HP variable frequency drive (VFD) running at a maximum

of 1800 revolutions per minute (RPM). The 1200 µm and 1500 µm corn were ground on the

coarse hammer mill, with a 100-HP motor and the VFD at a maximum of 1200 RPM. The use of

the VFD allows the mill to fine tune the PS. Wenger Feeds, LLC collected and recorded

information regarding the speed and amperage of the two respective hammer mill motors during

the grinding, as well as throughput in tonnes per hr (TPH), efficiency (KWh/tonne), cost per

KWhr and cost ($/tonne) and speed (hr/tonne) to grind whole corn to the different GMD reported

in Table 3-1. It should be noted that all values were calculated with the exception of TPH, which

was provided by Wenger Feeds, LLC as estimates from their feed processing. Therefore, TPH

values remain unchanged through Table 3-1 for this reason.

Sieving and Calculations

To determine the actual PS distribution of the 600, 900, 1200, and 1500 µm corn, three

samples were taken of each corn treatment from each Delivery (1 & 2) from random locations in

the 454 kg totes delivered from Wenger Feeds, LLC (Rheems, PA). The sieving and PS

measurements for all samples were measured in accordance with ASABE (2013) procedures.

Using a W.S. Tyler sieve shaker (W.S. Tyler Company, Cleveland, OH) in Penn State

University’s Department of Agricultural and Biological Engineering, each of the four corn

treatments were separated into three replicates of 100 g each, for a total of twenty-four 100 g

samples. Samples were shaken for 10 minutes each, with one additional minute until there was

less than a 0.1% mass change on the smallest screen. All tare weights of individual sieves were

taken before shaking, and at the conclusion of sieving. The mass of each of the sample materials

were recorded, and percent distribution was calculated, as shown in Tables 3-2 and 3-3. Percent

separation between treatments from Delivery 1 and Delivery 2 are shown in Figure 3-1, 3-2, 3-3,

23

and 3-4. The following set of calculations (ASABE, 2013) were used to determine mean

diameter, where 𝑑𝑔𝑤 is the geometric mean diameter of all particles by mass (1), 𝑆log is the log

of the mean diameter of all particles and stands for the geometric standard deviation of log-

normal distribution (2), and 𝑆𝑔𝑤 calculates the geometric standard deviation (GSD) of all particle

diameters by mass (3), with final geometric mean diameter (GMD) and standard deviation shown

in Table 3-4. In this case, GSD measures the amount of dispersion around the GMD.

(𝟏) 𝑑𝑔𝑤 = log−1 [∑ (𝑊𝑖 log �̅�𝑖)

𝑛𝑖=1

∑ 𝑊𝑖𝑛𝑖=1

]

(𝟐) 𝑆log = [∑ 𝑊𝑖(log �̅�𝑖 − log 𝑑𝑔𝑤)

2𝑛𝑖=1

∑ 𝑊𝑖𝑛𝑖=1

]

12

=𝑆ln

2.3

(𝟑) 𝑆𝑔𝑤 ≈1

2𝑑𝑔𝑤 [log−1𝑆log − (log−1𝑆log)

−1]

Statistical Analysis

Percent distributions between given screen sizes for all treatments were analyzed using

the PROC GLM procedure SAS 9.4 (SAS Institute, 2013) with Tukey’s test for multiple means

comparison with application of an arcsine transformation on all percentage data and significance

determined at a threshold of P ≤ 0.05 (Steel and Torrie, 1960).

Nutrient Analysis

Due to the duration of time between the dietary studies, there was the need to have two

batches of corn delivered. Corn treatments for the broiler digestibility, pullet and hen studies were

24

delivered as ground corn only to fabricate mash diets, whereas the corn utilized for the broiler

floor pen study was delivered as complete crumbled and pelleted commercial diets for each corn

PS treatment. The corn delivered in February of 2016 (Delivery 1), was used for the broiler

digestibility and pullet growth studies. The corn delivered in October of 2016, (Delivery 2), was

used for the hen and floor pen broiler studies. The corn for the broiler floor pen study was mixed,

pelleted, and crumbled by Wenger Feeds, LLC (Rheems, PA). Corn samples from Delivery 1 and

2 were analyzed separately for proximate analysis, amino acid concentration (ESCL, Columbia,

MO), and mineral concentration in triplicate for feed formulation purposes (Agricultural

Analytical Laboratory, University Park, PA) and shown in Table 3-5.

RESULTS AND DISCUSSION

Feed milling energy usage, efficiency, and economics for all four treatments (600, 900,

1200, and 1500 µm) for Delivery 1 and 2 provided by Wenger Feeds, LLC (Rheems, PA) are

shown in Table 3-1. Delivery 1 was similar to Delivery 2, and treatments were ground using the

same equipment for both Deliveries. By using the VFD on the hammer mills, power is slightly

variable between deliveries, and Delivery 2 corn required more greater power for all treatments

compared to Delivery 1. This same trend is also reflected in efficiency and cost with Delivery 2

being slightly less efficient and costlier than Delivery 1 ($0.51/tonne vs. $0.49/tonne for the 600

µm treatment). Both Delivery 1, 2, and the average of both deliveries show clear linear trends for

increased TPH as corn PS increases. Efficiency, cost/tonne, and hr/tonne all decrease linearly as

corn PS increases. The type of grain used with a specific hammer mill setting and screen has been

shown to influence the PS distribution produced, as previous work has shown corn and wheat run

though the same 1- and 7-mm hammer mill screens produce different results, where corn resulted

25

in a GMD of 297 µm and 528 µm, and wheat resulted in 284 µm and 890 µm PS, respectively

(Amerah et al., 2007, 2008).

Delivery 1 and 2 were evaluated separately for PS percent separation using the same

stack of sieves required for the ASABE procedure S319.4 to keep all measurements as

standardized as possible. Delivery 1, shown in Table 3-2, revealed the 3360 and 2380 µm screens

held the greatest percent (53.28%) of 1500 µm corn compared to 600, 900, and 1200 µm

treatment corn, while the remaining screens held no more than 13.89% each. Screen size 1680

µm interestingly was greatest for the 900 µm treatment corn, followed by the 600 µm corn, then

the 1500 µm and the 1200 µm corn. Screen openings 1190, 841, and 595 µm were not

significantly different between the 1200 and 1500 µm treatment corn.

Delivery 2, shown in Table 3-3, revealed the 3360, 2380, and 1680 µm screens held

significantly more of the 1500 µm corn (60.66%) than all other treatments. Screens 1190, 841,

595, and 420 µm held the greatest portion of the 600 µm corn (50.22%) compared to the 900,

1200 and 1500 µm treatments. At the 420 µm screen size, the 900 and 1200 µm screens held an

intermediate amount of corn and were not significantly different from each other (12.50 and

9.76%, respectively) compared to the 600 and 1500 µm treatments. Screens 149, 105, 74, and 52

µm were not significantly different between treatments and all screens in the range held between

3.18% - 3.56% of the total 100 g, though the 600 µm corn treatment also had significantly more

fines in the bottom pan compared to all other treatments (0.08 vs. 0.02, 0.02, and 0.01%).

Figures 3-1, 3-2, 3-3, and 3-4 compare screen distribution between the two deliveries for

each corn treatment (600, 900, 1200, and 1500 µm). In both Delivery 1 and 2, the 600 and 900

µm corn treatments track together, as do the 1200 and 1500 µm corn treatments. The comparison

between Delivery 1 and Delivery 2 for the 600 µm corns (shown in Figure 3-1) reveals Delivery 1

had a greater percentage of corn remaining in screens measuring 2380 µm and 1680 µm, whereas

Delivery 2 had a greater percentage of corn remaining in screens measuring 595 µm and 420 µm.

26

The 900, 1200, and 1500 µm treatments (Figures 3-2, 3-3, and 3-4) tracked very similarly

between Delivery 1 and Delivery 2 using the same procedure.

Geometric mean diameter and GSA were calculated and shown for all corn treatments

and both deliveries in Table 3-4. Within treatment and between Deliveries, GMDs for the 600 µm

treatment were very close at 703.21 and 702.69 µm, yet approximately 102.57 µm away from the

target PS of 600 µm. All corn treatments were within 250 µm of the goal PS of the current study.

The 900 µm calculated GMD values were very close, within 66 µm of each other in Delivery 1

and 2, and closely flanked the 900 µm target treatment. Delivery 1 and 2 GMD values for the

1200 µm treatment were within 26 µm of each other though were slightly lower than the goal of

1200 µm. Delivery 1 and 2 GMD were higher than the 1500 µm target, where Delivery 2 was

within 60 µm of the goal and Delivery 1was 214 µm greater than the 1500 µm target. Likewise,

GSD were very low herein compared to Reece et al. (1985) where roller mill (2.23 GSD) and

hammer mill (2.35 GSD) ground corn were compared.

Treatment corn from both Delivery 1 and Delivery 2 were both analyzed for proximate

nutrients (crude protein, ether extract, crude fiber, ash and dry matter), along with amino acid

(AA) and mineral concentrations (Table 3-5). These were necessary for accurate feed formulation

of the respective studies. Delivery 1 and Delivery 2 corns were approximately 100 Kcal/kg

different in metabolizable energy (ME) (3178.90 vs. 3293.83 Kcal/kg) and crude protein (CP)

(7.75 vs. 7.56%). Delivery 1 corn showed lower ether extract (EE) and greater percent ash

compared to Delivery 2 corn (1.76 vs. 3.69% EE; 2.40 vs. 1.45% ash) which impacted their final

ME values. The reduced percent ash in Delivery 2 reflects clearly onto the lower calcium, iron,

manganese, and zinc levels in Delivery 1 corn and are reflected in the lower ash content, where

calcium of Delivery 2 corn is 0.09% vs. Delivery 1 corn at 0.42%, and iron was 28.17 mg/kg in

Delivery 2 corn versus 41.17 mg/kg in Delivery 1 corn. Manganese, similarly, was decreased for

Delivery 2 corn at 10.74 mg/kg versus 29.93 mg/kg in Delivery 1 corn. Lastly, zinc shows the

27

same trend as the previous minerals, with Delivery 2 zinc reduced at 31.75 mg/kg versus 51.30

mg/kg in Delivery 1 corn. Any variations in nutrient density of Delivery 1 and 2 corn may have

varied due to growing region, as well as a potential of soil contaminated corn in Delivery 1.

Sieving of the corn clearly showed the treatment separation of PS as planned for the

study, with very close GMD to the set goal, and low accompanying GSD values, within 0.30-

0.47. Less amperage, power, and cost were associated with greater feed TPH for the larger PS

corn. There was a very linear response, with smaller particle corn having less TPH and greater

associated cost and time needed to grind compared with larger PS having greater TPH and less

grinding cost and time required. Hammer mill grinding is normally less uniform compared to

roller mill grinding. The results herein indicated the GSD to be less than 0.47. Differences in

VFD motor speed, screen size, along with percent moisture of corn could potentially affect the

final product. Energy expenditures from the feed mill strongly indicate that the energy costs

associated with PS reduction could be of as a source of cutting costs without negatively affecting

bird performance.

ACKNOWLEDGEMENTS

This study was funded through the 2015 Pennsylvania Poultry Industry Egg and Broiler

Research Check-off Program.

REFERENCES



455.

28




ASABE. 2008. Method of determining and expressing fineness of feed materials by sieving:

American Society of Agricultural and Biological Engineers S319.4 Feb 2009 (Rev. 2012).

St. Joeseph, MI.

CPM. 2017. Economics of grinding for pelleted feeds. Available at

http://www.cpm.net/downloads/Economics of Grinding for Pelleted Feeds.pdf.




Healy, B. J., J. D. Hancock, G. A. Kennedy, P. J. Bramel-Cox, K. C. Behnke, and R. H. Hines.


Sci. 72:2227–2236.






Portella, F. J., S. Leeson, and L. J. Caston. 1988. Apparent feed particle size preference by laying

hens. Can. J. Anim. Sci. 68:915–922.



Sci. 64:1834–1839.

SAS Institute. 2013. SAS User’s Guide: Version 9.4. Cary, NC.

Steel, R. G. D., and J. H. Torrie. 1960. Principles and procedures of statistics, a biometrical

approach. McGraw-Hill Kogakusha, Ltd., Tokyo, Japan.

29

Table 3-1. Hammermill economic cost (average amperage, power, TPH, efficiency, cost/tonne &

hr/tonne)

Delivery 1

Treatment Avg.

amperage

Power

(KW)

TPH

(tonnes/h)

Efficiency

(KWhr/tonne)

USD$/tonne

($0.0739/KWhr) hr/tonne

600 µm 135 101.01 16 6.19 0.46 0.061

900 µm 135 101.01 20 5.06 0.37 0.050

1200 µm 75 56.12 24 2.38 0.18 0.042

1500 µm 65 48.63 27 1.79 0.13 0.037

Delivery 2

Treatment Avg.

amperage

Power

(KW)

TPH

(tonnes/h)

Efficiency

(KWhr/tonne)

USD$/tonne


600 µm 150 112.23 16 6.87 0.51 0.061

900 µm 150 112.23 20 5.62 0.42 0.050

1200 µm 75 56.12 24 2.38 0.18 0.042

1500 µm 75 56.12 27 2.06 0.15 0.037

Average of Deliveries 1 & 2

Treatment Avg.

amperage

Power

(KW)

TPH

(tonnes/h)

Efficiency

(KWhr/tonne)

USD$/tonne


600 µm 142.5 106.62 16 6.53 0.48 0.061

900 µm 142.5 106.62 20 5.34 0.39 0.050

1200 µm 75 56.12 24 2.38 0.18 0.042

1500 µm 70 52.38 27 1.92 0.14 0.037

30


Treatment

600 µm 900 µm 1200 µm 1500 µm SEM P-value

Screen size3

3360 0.26c

0.75c

15.43b

21.19a

2.76 <0.0001

2380 6.76d

14.43c

22.79b

32.09a

2.86 <0.0001

1680 16.06b

18.87a

11.88d

13.89c

0.79 <0.0001

1190 16.74a

15.52b

9.53c

9.51c

1.01 <0.0001

841 11.41a

10.16b

6.38c

5.79c

0.73 <0.0001

595 9.16a

8.37a

5.26b

4.09b

0.64 <0.0001

420 7.38a

7.62a

4.35b

2.92c

0.62 <0.0001

297 6.07a

6.39a

6.66a

2.47b

0.56 0.0006

210 11.13a

10.65a

9.42a

2.09b

1.11 <0.0001

149 6.13a

3.57ab

3.56b

1.51b

0.55 0.0019

105 8.29a

3.41b

4.13b

2.95b

0.69 0.0021

74 0.35ab

0.13b

0.37ab

0.62a

5.97 0.0049

53 0.08b

0.08b

0.11b

0.47a

5.23 0.0002

Bottom Pan4

0.18b

0.05b

0.13b

0.41a

4.47 0.0022 a-d

Means within the same column with no common superscript differ significantly (P ≤ 0.05). 1 All corn analyses were done in triplicate with the shaker running for 11 minutes per sample.

2 All samples for each treatment and Delivery were analyzed in triplicate.

3 Screens were measured in µm per internal screen hole diameter.

4 Bottom pan catches any remaining fines that were shaken to the bottom of the stack.

31


Treatment

600 µm 900 µm 1200 µm 1500 µm SEM P-value

Screen size3

3360 0.07c

0.47c

5.02b

12.60a

1.53 <0.0001

2380 1.91d

7.82c

22.76b

30.99a

3.50 <0.0001

1680 7.90b

15.81a

16.36a

17.07a

1.16 <0.0001

1190 15.43a

16.08a

14.07a

11.80b

0.54 0.0009

841 15.40a

12.25b

9.25c

7.09d

0.95 <0.0001

595 19.39a

12.35b

7.40c

5.43c

1.68 <0.0001

420 17.30a

12.50ab

9.76ab

4.44b

1.64 0.0035

297 10.58ab

12.44a

5.49b

4.96b

1.10 0.0037

210 8.44a

6.75a

5.43ab

3.14b

0.66 0.0024

149 2.23

2.28 2.13 1.71 0.12 0.3687

105 1.20 1.16 1.52 1.26 0.08 0.4427

74 0.04 0.04 0.03 0.14 0.02 0.1961

53 0.04 0.03 0.05 0.07 0.01 0.4635

Bottom Pan4

0.08a

0.02b

0.02b

0.01b

0.01 0.0378 a-d

Means within the same column with no common superscript differ significantly (P ≤ 0.05). 1 All corn analyses were done in triplicate with the shaker running for 11 minutes per sample.

2 All samples for each treatment and Delivery were analyzed in triplicate.

3 Screens were measured in µm per internal screen hole diameter.

4 Bottom pan catches any remaining fines that were shaken to the bottom of the stack.

32

Figure 3-1. Corn particle size percent separation: 600 µm Delivery 1 vs. Delivery 2

0

5

10

15

20

25

30

35

Am

ou

nt

(%)

Screen Size (µm)

Delivery 1

Delivery 2

33

Figure 3-2. Corn particle sieving percent separation: 900 µm Delivery 1 vs. Delivery 2

0

5

10

15

20

25

30

35

Am

ou

nt

(%)

Screen Size (µm)

Delivery 1

Delivery 2

34


0

5

10

15

20

25

30

35

Am

ou

nt

(%)

Screen Size (µm)

Delivery 1

Delivery 2

35


0

5

10

15

20

25

30

35

Am

ou

nt

(%)

Screen Size (µm)

Delivery 1

Delivery 2

36

Table 3-4. Corn treatment particle size sieving: GMD and GSD1,2

Delivery 1

Treatment GMD (µm) ± GSD

600 µm 703.21 ± 0.43

900 µm 913.06 ± 0.40

1200 µm 1166.46 ± 0.47

1500 µm 1714.68 ± 0.41

Delivery 2

Treatment GMD (µm) ± GSD

600 µm 702.69 ± 0.30

900 µm 847.07 ± 0.34

1200 µm 1192.59 ± 0.38

1500 µm 1560.17 ± 0.37 1 Geometric standard deviation (GSD) is defined as the

standard deviation of log-normal distribution by mass in ten-

based logarithm (ASABE Standard S319.4, 2013). 2 All samples for each treatment and Delivery were analyzed

in triplicate.

37

Table 3-5. Nutrient composition of corn (“as is” basis)1

Delivery 1

Delivery 2

Nutrient (%)

ME (Kcal/kg)2

3178.90 3293.73

NFE2 73.75 72.59

Dry matter 87.29 87.19

Crude protein 7.75 7.56

Ether extract 1.76 3.69

Crude fiber 1.63 1.90

Ash 2.40 1.45

Amino acids (%)

Aspartic Acid 0.51 0.50

Threonine 0.28 0.27

Serine 0.33 0.33

Glutamic Acid 1.30 1.32

Proline 0.58 0.63

Glycine 0.31 0.29

Alanine 0.51 0.52

Cysteine 0.16 0.16

Valine 0.35 0.34

Methionine 0.17 0.17

Isoleucine 0.28 0.26

Leucine 0.84 0.86

Tyrosine 0.18 0.23

Phenylalanine 0.35 0.36

Lysine 0.30 0.26

Histidine 0.23 0.20

Arginine 0.34 0.34

Mineral (%)3

Calcium 0.42 0.09

Total phosphorus 0.33 0.30

Potassium 0.34 0.36

Magnesium 0.09 0.10

Sulfur 0.10 0.11

Sodium (mg/kg) 23.48 27.13

Iron (mg/kg) 41.17 28.17

Copper (mg/kg) 5.15 3.05

Manganese (mg/kg) 29.93 10.74

Zinc (mg/kg) 51.30 31.75 1 All samples for each treatment and Delivery were analyzed in

triplicate. 2 Corn was donated by cooperator Wenger Feeds, LLC (Rheems, PA)

and nutrient values were analyzed by ESCL (Columbia, MO). ME

(kcal/kg) was calculated using the NRC (1994) equation 36.21 x CP +

85.44 x EE + 37.26 x NFE (for corn grain). 3 Nitrogen free extract (NFE) was calculated using the equation NFE =

DM - Ash - CP - CF – EE (National Research Council, 1994). 4 Mineral values were obtained from the Agricultural Analytical

Laboratory at The Pennsylvania State University (University Park, PA).

38

Chapter 4

EFFECT OF CORN PARTICLE SIZE ON APPARENT AND TRUE ILEAL

DIGESTABILITY AND JEJUNUM VISCOSITY OF 35-DAY OLD MALE

BROILERS

ABSTRACT

Corn particle size (PS) treatments were compared utilizing digestibility, feed intake,

growth, and conversion of broiler chickens. Day old Cobb-500 male broilers (196) were placed

into 17 battery cages with 10-16 birds per cage. Birds were fed a standard starter and grower diet

to 29 d. At 14 days of age, birds were redistributed into 35 battery cages with 5 birds per cage for

the corn particle size treatment diets and 8 birds per cage for the protein-free (PF) diet. From days

29-30 birds transitioned to one of the five treatment diets comprised of (600 µm, 900 µm, 1200

µm, or 1500 µm PS corn, or PF). The PF diet contained only dextrose monohydrate as the sole

energy source. At 35 d birds were euthanized and ileal and jejunum portions of the intestine were

harvested for apparent, true and standardized digestibility determination. All data was analyzed

using a one-way ANOVA with the mixed procedure of SAS 9.4 and Tukey’s range test for means

comparison when necessary. There were significant differences (P < 0.05) between treatments at

35 d for body weight (BW) and 28 – 35 d body weight gain (BWG). Apparent digestibility of

Met, Lys, Ile, Pro, Tyr, and Gly were significantly less for broilers fed 600 µm and compared to

the other PS. True digestibility yielded no statistically significant results, but with standardized

endogenous losses from the literature, Met digestibility was again decreased for broilers fed the

600 µm test feed. Jejuna digesta viscosity, measured in centipoise, was highest among birds fed

the 600 and 900 µm PS. In conclusion, PS influences broiler growth performance and at 35 d

39

larger particles in a mash diet lend themselves to greater apparent and true digestibility, less

viscous digesta, allowing better gastrointestinal tract flow, improved nutrient uptake and, as a

result, better live performance.

INTRODUCTION

In the United States, a standard broiler diet consists of approximately 60% corn (Leeson

and Summers, 2005), however prices have been increasing and availability has been decreasing

over the past decade as ethanol production has taken from 10% to 30% of the US corn crop

(Donohue and Cunningham, 2009). To continue raising broilers for United States consumers and

to increase production in the future as the world population continues to rise, there is a need to

hone in on an optimum corn particle size (PS) to allow for greater bird efficiency with the US

corn available to feed mills.

Previous work has shown pellet processing can further reduce particle size, as larger

particles tend to be broken between pellet rollers and the die (Engberg et al., 2002; Péron et al.,

2005). No differences were seen in bird performance when the pelleting process evened out

differences in wheat particle size in the study by Engberg et al. (2002). In mash form, larger feed

particles are more easily consumed as birds age due to beak size (Morgan and Heywang, 1941).

Beak size and gape has been shown to influence PS preference in broilers. Previous work by

Portella et al. (1988) has shown broilers choose feed based solely on particle size and the more

uniform a diet is, the less time a bird will spend searching for larger, less uniform particles (Nir et

al., 1994a). Additionally, as a birds’ gape increases with age, chickens have been found to prefer

larger feed particles as well. The same study also reported 21 day old birds fed medium or coarse

mash diets had improved BW and BWG over those fed a finely ground mash diet (Nir et al.,

1994b). As poultry nutritionists are able to feed with greater precision, it becomes increasingly

40

important to accurately measure apparent ileal digestibility (AID) and true ileal digestibility

(TID) of not only ingredients but also the particle size of corn and other cereals, as varying

geometric mean diameter (GMD) has been shown to influence nutrient utilization and growth

performance (Reece et al., 1985, 1986). Varying corn PS affects broiler growth performance and

apparent and true ileal digestibility.


Birds and Housing

Day old male Cobb 500 broiler chicks (196) were obtained from a local hatchery

(Elizabethtown, PA). Chicks were randomly placed into 17 battery cages with 10-16 birds per

cage (372 – 232 cm2/bd). At 14 days of age, birds were redistributed into 35 battery cages with 5

birds per pen for all corn diets and 8 birds per cage for the PF diet, with 7 replicate cages for each

treatment (743 – 465 cm2/bd). All management practices were maintained throughout the study as

recommended by Cobb-Vantress (2012). The room’s temperature began at 32.2°C at day 0 of the

study, and was gradually decreased to 21.1°C by day 14 where it remained for the duration of the

study. Birds were fed a commercial starter diet from day 0-14 and a commercial grower from day

14-28, and were transitioned to the treatment diets (33% treatment diet, 66% control) on day 29,

and day 30 (66% treatment diet, 33% control) and fed 100% treatment diets from day 31-35. On

day 28, before beginning transition to treatment diets, birds were weighed individually and

redistributed as necessary to achieve a uniform body weight between replicate treatment cages.

All birds were provided water ad libitum and feed according to the procedure below. All

techniques and procedures involving the birds in this study were approved by The Pennsylvania

State University Institutional Animal Care and Use Committee (IACUC Protocol #46838).

41

Treatment Diet Formulation for the Digestibility Assay

All corn dietary treatments contained 857.4 g/kg of the test ingredient, as either 600, 900,

1200, or 1500 μm PS corn (Table 4-1). The PF diet was formulated with dextrose monohydrate

(My Spice Sage, Yonkers, NY) as the only carbohydrate source (84.34%) and was included at 5%

in all corn diets. All diets were formulated to contain 2% Celite (Sigma-Aldrich Co., St. Louis,

MO), which was mixed at a 2:3 ratio of Celite 110 and 281, 0.80% vitamin and trace mineral

premix, and 0.50% salt. To keep all treatment diets at the same percent calcium and phosphorus

levels, limestone was added to all corn diets at 0.61% and the PF diet at 1.37% and di-calcium

phosphate was added to the corn diets at 1.55%, and the PF diet at 1.99%. Additionally, both diets

included corn oil at 3.8% for the corn diets and 6.0% for the PF, and the PF diet also included

3.0% cellulose. Upon analysis, each respective corn treatment diet (600, 900, 1200, or 1500 μm)

averaged 7.25, 7.56, 7.78, and 7.94% crude protein (CP), for 600, 900, 1200, and 1500 μm,

respectively, and a calculated metabolizable energy (ME) of 3,274 kcal/kg. All analyzed amino

acids (AA) were similar across corn treatment diets, while analyzed AA for the PF diet was zero.

Digestibility Assay

At 35 days of age, birds were fasted overnight for 8 hours and re-fed their respective

treatment diet for 4 hours before being euthanized (Kadim and Moughan, 1997) to improve

uniformity of treatment birds and gut fill for the purpose of collecting ileal digesta samples,

which were collected from each bird per replicate cage (n = 5 birds/cage for all corn PS treatment

cages, and n = 8 for all PF cages) by gently squeezing from the terminal end of the jejunum at

Meckel’s diverticulum, to approximately ~1 cm proximal to the ileal-cecal junction into a pooled

100 ml sample cup per replicate cage placed on ice. Once transported back to the lab, samples

42

were frozen at -20°C until being freeze dried. After freeze drying, samples were thoroughly

ground with a mortar and pestle and pooled to achieve a minimum of 10 g per sample for

analysis. The yield of dried ileal digesta influenced the number of replicate samples that could be

analyzed per treatment (PF, n = 3; 600 μm, n = 4; 900 μm, n = 5; 1200 μm, n = 5; 1500 μm, n =

4).

Viscosity Assay

Jejuna digesta samples were collected from the end of the duodenal loop to Meckel’s

diverticulum from each replicate cage (5 birds per cage for all four corn treatments and 8 birds

per cage for each PF diet cage) by gently squeezing contents into a pooled sample cup for each

replicate cage. Jejuna digesta samples were placed on ice and brought back to the laboratory

where they were kept refrigerated until analysis. Each jejuna sample was homogenized using a

sterile stirring rod, evenly distributed into two 16 ml Eppendorf tubes with plastic Pasteur

pipettes, and then centrifuged at 14,000 revolutions per minute (RPM) at 4°C for 5 minutes. The

supernatant liquid (0.5 ml) from the jejuna samples was harvested off the surface and measured

using a digital viscometer (Brookfield model DV-II+, Brookfield AMETEK, Inc., Middleboro,

MA) at 25°C and a spindle speed of 30 RPM. Each sample was read after 30 seconds. The

average viscosity of each pair of Eppendorf tubes’ (one pair of tubes for each replicate cage) was

used as a replicate, with a total of 7 replicate measurements per treatment.

Nutrient Analysis of Digesta and Complete Treatment Diets

Replicate treatment diets (n = 3) and all pooled freeze-dried ileal samples were analyzed

at the ESCL using AOAC (2006) method 982.30 E (a,b) to measure the complete AA profile with

43

the exception of tryptophan and method 990.03 to determine CP and method 934.01 (using a

vacuum oven) to determine moisture for diets and digesta. Additionally, method 942.03 was used

to determine acid insoluble ash content, method 920.39 (A) was used to analyze for ether extract

(EE) (by ether extract), and crude fiber (CF) was determined by method 978.10.

Calculations

Apparent and true ileal amino acid digestibility were calculated on a dry matter (DM)

basis according to methods reported by Lemme et al. (2004), Burley (2012), and Li (2015), where

diet samples analyzed in triplicate (ESCL, Columbia, MO) and averaged for AA and acid

insoluble ash (AIA) were used in the calculation. Measurements of ileal digestibility are used to

ascertain estimated AA bioavailability. Apparent ileal digestibility (AID), which measures AA

bioavailability as-is from collected bird digesta, and true ileal digestibility (TID), which

standardizes AID bioavailability using the ileal endogenous amino acid losses (EAAL) from the

PF treatment birds, were calculated for each sample and then averaged for each treatment. By

pooling PF bird replicates (n = 3), EAAL were determined by freeze drying samples and analysis

at the ESCL using AOAC (2006) method 982.30 E (a,b) to measure AA concentrations, and

AOAC method 492.03 to determine acid insoluble ash content. All equations below use the

following terms: AAdiet is the AA concentration (%) in the diet, AAdigesta is the AA

concentration (%) in the digesta sample, AIAdiet is the acid insoluble ash concentration from

addition of Celite to the diets, and AIAdigesta is the acid insoluble ash concentration from the

dietary addition of Celite in the digesta samples, all on a DM basis. Additionally, a second TID

(TIDLit) was calculated using published EAAL values (Lemme et al., 2004) from five replicated,

experiments using enzymatically hydrolyzed casein, rather than ones measured herein, called

EAALLit. The endogenous ileal AA losses (g/100g DM) used to calculate the TIDLit were as

44

follows: Met, 0.0079; Cys, 0.0143; Lys, 0.0169; Thr, 0.0571; Arg, 0.0216; Ile, 0.0390; Leu,

0.0381; Val, 0.0449; His, 0.0209; Phe, 0.0237; CP, 0.9234 (Lemme et al., 2004).

(1) Apparent AA digestibility:

AID = ((AIAdiet × AAdigesta)/(AIAdigesta × AAdiet) × 100)

(2) Endogenous ileal digesta AA losses from PF diet and digesta AA values (g/ 100 g DM):

EAAL = (AAdigesta × AIAdiet)/(AIAdigesta)

(3) True AA digestibility (g/100 g DM):

TID = [AID + (EAAL/AAdiet)] × 100

(4) True AA digestibility with EAAL values from the literature (g/100 g DM):

TIDLit = [AID + (EAALLit/AAdiet)] × 100


Data was analyzed using a one-way ANOVA in the MIXED procedure of SAS software

version 9.4 (SAS Institute, 2013) where statistical significance was defined at P ≤ 0.05 and

differences between treatments were identified using Tukey’s test for multiple mean comparisons

(Steel and Torrie, 1960).

45


In this study, four differently ground corn particle sizes were evaluated to determine their

impact on digestibility for broilers. Nutrients in the Delivery 1 corn previously described in Table

3-5 (Kitto, 2017), were used exclusively for this study. Both diet formulation and nutrient

analysis and AA concentrations of all four treatment diets and the PF diet are shown in Table 4-1.

While all four treatment diets were formulated to be isocaloric and isonitrogenous, nutrient

analysis shows CP concentrations increasing as PS increases, through all corn treatments. The PF

diet had a higher CP level than expected, although similar results have been seen previously in

diets which were formulated to be PF (Burley, 2012; Li, 2015).

Body weight was not different between treatments at day 28 as birds started the transition

from the control diet to their treatment diets (Table 4-2). At day 35 PF birds were significantly

lighter than the 600, 900, and 1200 µm corn treatments. Birds fed 1500 µm were not different

from the PF or 600 and 900 µm fed birds and the BWG of birds between day 28-35, was

significantly greater for the 600, 900, and 1200 µm treatments compared to the 1500 µm and PF.

Birds fed the 1500 µm treatment diet were observed to be selecting finer particles from their

diets, and leaving the larger particles behind as orts. Portella et al., (1988) has observed reduced

BW and BWG when birds spent additional time selecting feedstuffs. Furthermore, selection of

small PS may be due to the physical size of the birds as Nir et al. (1994b) noted the small beak

and gape of the throat influenced large PS consumption. Lastly, the birds herein were slightly

reduced in BW overall compared to the Cobb-500 broiler management guide (Cobb-Vantress,

2012) as the raised wire floor batteries may have impaired growth.

Endogenous AA losses (Table 4-3) were calculated from equation (2) above and were

found to be far greater, ranging from 0.03 – 0.19 g/100g DM, than previous work by Burley

(2012). As a result of these greater EAAL values, TID calculations resulted in values over 100%.

46

The inherently low protein concentration of the corn evaluated herein could explain the TID

values and why Burley (2012) did not have TID values over 100%, as the ingredients diets from

that study ranged from 11.82 – 19.80% CP, whereas the ones used in this study ranged from 7.25

– 7.94%. One explanation for TID values greater than 100% can be from higher endogenous AA

losses for corn and also its inherent low CP concentration. Past work has noted the same issue

when evaluating low CP corn for TID with broilers raised to 21 days of age (Adedokun et al.,

2008), Peking ducks raised to 26 days of age (Kong and Adeola, 2013), and in growing pigs

(Stein et al., 2005). Furthermore, broilers raised to 5 weeks of age and given a low CP wheat

(9.2%) as a test ingredient resulted in TID values over 100% according to Kadim et al. (2002).

Previous work from Lemme et al. (2004) indicates that test ingredients naturally low in AA more

greatly affect TID calculations than those with inherently high AA concentrations. Endogenous

AA losses more greatly influence the TID calculation when AAdiet or AAdigesta are lower, as with

cereal grains or a legume. For example, wheat, with 13% CP can express a difference of 75%

AID versus 86% TID, as EAAL values cause overestimation of AA digestibility in those

inherently lower AA concentrated ingredients (Lemme et al., 2004). These authors came to the

conclusion that low corn CP levels are highly affected by the relative EAAL and results in TID

values over 100%. Another possible explanation and one that works in concert with the low corn

CP and AA concentrations would be greater EAAL from PF fed birds versus birds fed diets

including a test ingredient with adequate levels of protein (Siriwan et al., 1993). Additionally,

high endogenous losses could have resulted from too much pressure squeezing the ileum, pushing

mucous out along with the digesta and adding to the endogenous losses. Lastly, while previous

studies have sampled from the whole ileum without adverse effects, it is possible higher EAAL

values come from utilization of the whole ileum (from Meckel’s diverticulum to approximately 1

cm proximal to the ileo-cecal junction), rather than utilization of only two-thirds of the ileum

47

mostly distal from Meckel’s diverticulum. As previous work has shown there are fewer nutrients

absorbed in the first third of the ileum posterior to Meckel’s diverticulum (Kluth et al., 2005).

Apparent ileal AA digestibility calculations from equation (1) and analysis results are

shown in Table 4-4. The 600 µm treatment was found to have the lowest AID for Met, Lys, Ile,

Pro, Tyr, and Gly. Overall, apparent digestibility ranged from 59.04% (for 600µm Thr) to 87.11%

(for 900 µm Met). Ser approached significance with the 900 µm digestibility greater than the

other corn treatments at 75.31% AID. When AID was graphed including all the treatment results,

a second order polynomial line revealed a strong relationship between PS and AA digestibility

with an R2 value of 0.955 and the digestibility trend line peak at 1265.6 µm based on the data

herein (Figure 4-1).

Total ileal AA digestibility was calculated using equation (3), and the EAAL values

from the study herein (Table 4-5). The range of TID was from 92.28% for Gly to 106.27% for

Lys and were not significantly different between treatments for any AA measured, although a

repeating numerical trend indicated the 600 µm corn had lower TID values compared to 900,

1200, and 1500 µm PS treatments for both individual AA and overall as was observed for AID.

When the TID results were similarly graphed with a second order polynomial line for total AA

digestibility had an R2 value of 0.9895 and a peak value of 1237.50 µm (Figure 4-2) very similar

to the AID results shown in Figure 4-1. These results indicate that while there are no significant

TID differences between treatments for any AA evaluated, the trend line was highly correlated

with the AA digestibility values for each treatment. As previously discussed, because high EAAL

values resulted in TID values over 100% in the current study, a set of standardized EAAL values

from Lemme et al. (2004) were another approach utilized to calculate TID without concern for

high EAAL. As indicated by Lemme et al. (2004), when test ingredients have naturally low CP

concentrations, the standardization step calculating TID using EAAL values can greatly

overestimate the AAdiet and AAdigesta. Therefore, the standardized EAALLit from Lemme et al.

48

(2004) sought to rectify any overestimations caused by this study’s EAAL values using values

which were repeated five times, using enzymatically hydrolyzed casein (EHC). The TIDLit values

were recalculated using EAALLit values in equation (4), and results shown in Table 4-6. Results

for TIDLit were not significant, save Met, where the 600 µm treatment was reduced compared to

the other PS treatments and a (P < 0.10) numerical trend for Lys. Overall values were

consistently lower for the 600 µm corn treatment among all AA and for the overall mean

compared to the other PS treatments. Figure 4-3, TIDLit, shows this as well, with an R2 = 0.9995

and second order polynomial trend line indicating the AA digestibility peaked at a PS of 1362.50

µm. The apparent and true ileal AA digestibility peak PS tracked more closely together at 1265.6

and 1237.50 µm, respectively, compared to the literature TIDLit, which peaked at 1362.50 µm.

Jejunum digesta viscosity was measured, and the 900 µm treatment was significantly

greater than the PF, 1200 and 1500 µm treatments (Table 4-7). The 600 µm viscosity was

intermediate and insignificantly different from the other corn PS treatments. Broilers fed finely

ground mash feed have historically been found to have lower BWG and FI, possibly due to

reduced flow through the gastrointestinal tract caused by high digesta viscosity (Yasar, 2003).

Jejunum viscosity measurements were highest for 600 and 900 µm treatments, indicating

decreased gastrointestinal movement, nutrient digestibility, and growth. The AID of Met, Lys, Ile,

Pro, Tyr, and Gly were decreased for the 600 µm treatment compared to the other PS, and while

there were no significant results in TID, the TIDLit evaluation resulted in similar results for Met

digestibility compared to the 900, 1200, or 1500 µm.

There were significant differences between treatments for BW at 35 days of age, with

1200 µm treatment birds being significantly heavier than 1500 µm or PF birds, which agrees with

AID and TID digestibility findings seen in Figure 4-1 and 4-2. While this could be due to the

1500 µm fed birds selectively choosing the finer particles from their mash feed, the results agree

with digestibility findings. The 28-35 day BWG was greater for the 600, 900 and 1200 µm

49

treatments and reduced for 1500 µm treatment broilers. The lowest and best viscosity was the

1200 µm treatment which corresponds closely with AID, TID, and TIDLit results, indicating the

1200 µm treatment birds had the highest nutrient absorption between the corn treatments. Body

weight and BWG results corroborate viscosity and digestibility results and indicate the 1200 µm

corn particle diet allowed growing broilers the most optimum nutrient absorption, growth

performance based on jejunum viscosity, AID and TID digestibilities, as well as the best BW and

BWG through 35 days of age. For broilers in the later stages of life, these results indicate

improved growth and nutrient absorption when fed 1200 µm corn and, when paired with

decreased milling costs, the 1200 µm corn treatment may be most beneficial for both mill savings

and improved bird performance.

ACKNOWLEDEMENTS

This study was funded through the 2015 Pennsylvania Poultry Industry Broiler Research

Check-off Program.

REFERENCES

Adedokun, S. A., O. Adeola, C. M. Parsons, M. S. Lilburn, and T. J. Applegate. 2008.

Standardized ileal amino acid digestibility of plant feedstuffs in broiler chickens and turkey

poults using a nitrogen-free or casein diet. Poult. Sci. 87:2535–2548.

AOAC, 2006. Official Methods of Analysis. AOAC Int., Gaithersburg, MD.

Burley, H. K. 2012. Enrichment of methionine from naturally concentrated feedstuffs for use in

organic poultry diets. PhD dissertation. Penn State Univ., University Park, PA.

50

Cobb-Vantress. 2012. Cobb 500 Broiler Performance & Nutrition Supplement Guide. Available

at http://www.cobb-vantress.com/docs/default-source/cobb-500-

guides/Cobb500_Broiler_Performance_And_Nutrition_Supplement.pdf (verified 2 October

2016).






Kadim, I. T., and P. J. Moughan. 1997. Development of an ileal amino acid digestability assay for

the growing chicken - effects of time after feeding and site of sampling. Brit. Poult. Sci.

38:89–95.

Kadim, I. T., V. Ravindran, and P. J. Moughan. 2002. Ileal amino acid digestibility assay for the

growing meat chicken - comparison of ileal and excreta amino acid digestibility in the

chicken. Brit. Poult. Sci. 43:588–597.

Kitto. 2017. Chapter 3. Corn particle separation and hammermill performance. MS. Penn State

Univ. University Park, PA.

Kluth, H., K. Mehlhorn, and M. Rodehutscord. 2005. Studies on the intestine section to be

sampled in broiler studies on precaecal amino acid digestibility. Arch. Anim. Nutr. 59:271–

279.

Kong, C., and O. Adeola. 2013. Comparative amino acid digestibility for broiler chickens and

White Pekin ducks. Poult. Sci. 92:2367–2374.



Lemme, A., V. Ravindran, and W. L. Bryden. 2004. Ileal digestibility of amino acids in feed

ingredients for broilers. World Poult. Sci. J. 60:423–438.

51

Li, S. 2015. Naturally concentrated methionine-rich feedstuffs for organic broiler production. MS

thesis. Penn State Univ. University Park, PA.






Sci. 73:45–49.








Sci. 64:1834–1839.

Reece, F. N., B. D. Lott, and J. W. Deaton. 1986. The effects of hammer mill screen size on

ground corn particle size, pellet durability, and broiler performance. Poult. Sci. 65:1257–

1261.


Siriwan, P., W. L. Bryden, Y. Mollah, and E. F. Annison. 1993. Measurement of endogenous

amino acid losses in poultry. Br. Poult. Sci. 34:939–949.

Steel, R. G. D., and J. H. Torrie. 1960. Principles and Procedures of Statistics, a Biometrical

Approach. McGraw-Hill Kogakusha, Ltd., Tokyo, Japan.

52

Stein, H. H., C. Pedersen, A. R. Wirt, and R. A. Bohlke. 2005. Additivity of values for apparent

and standardized ileal digestibility of amino acids in mixed diets fed to growing pigs. J.

Anim. Sci. 83:2387–2395.

Yasar, S. 2003. Performance, gut size, and ileal digesta viscosity of broiler chickens fed with a

whole wheat added diet and the diets with different wheat particle sizes. Int. J. Poult. Sci.

2:75–82.

53

Table 4-1. Nutrient composition of experimental diets for digestibility (“as is” basis)

Diet1

PF 600 µm 900 µm 1200 µm 1500 µm

Ingredient (%)

Corn - 85.74 85.74 85.74 85.74

Dextrose 84.34 5.00 5.00 5.00 5.00

Cellulose 3.00 - - - -

Corn oil 6.00 3.80 3.80 3.80 3.80

Celite

2.00 2.00 2.00 2.00 2.00

Dical P 1.99 1.55 1.55 1.55 1.55

Limestone 1.37 0.61 0.61 0.61 0.61

Vit-TM premix2

0.80 0.80 0.80 0.80 0.80

Salt 0.50 0.50 0.50 0.50 0.50

Calculated composition

ME (kcal/kg) 3,656 3,274 3,274 3,274 3,274

Crude protein 0.00 6.64 6.64 6.64 6.64

Analyzed nutrients (%)3

Dry matter 90.75 88.38 88.69 88.72 88.45

Crude protein 0.81 7.25 7.56 7.78 7.94

Ether extract 3.31 4.39 4.96 4.30 3.99

Crude fiber 1.75 2.08 1.94 2.24 2.01

Ash 5.96 7.30 6.98 6.70 6.89

Aspartic Acid 0.00 0.50 0.53 0.52 0.52

Threonine 0.00 0.25 0.28 0.26 0.26

Serine 0.00 0.28 0.32 0.31 0.31

Glutamic Acid 0.00 1.18 1.27 1.23 1.31

Proline 0.03 0.51 0.53 0.44 0.58

Glycine 0.01 0.29 0.31 0.33 0.31

Alanine 0.00 0.47 0.50 0.50 0.52

Cysteine 0.00 0.16 0.16 0.16 0.16

Valine 0.00 0.33 0.35 0.35 0.35

Methionine 0.00 0.16 0.18 0.16 0.17

Isoleucine 0.00 0.26 0.28 0.28 0.29

Leucine 0.02 0.77 0.81 0.79 0.86

Tyrosine 0.00 0.28 0.28 0.29 0.30

Phenylalanine 0.00 0.33 0.35 0.34 0.36

Lysine 0.00 0.38 0.45 0.40 0.40

Histidine 0.00 0.18 0.19 0.19 0.20

Arginine 0.00 0.33 0.36 0.36 0.35 1 PF = protein-free diet for endogenous amino acid loss determination; 600µm = Diet containing corn with a

majority particle size of 600 micrometers; 900µm = Diet containing corn with a majority particle size of 900

micrometers; 1200µm = Diet containing corn with a majority particle size of 1200 micrometers; 1500µm =

Diet containing corn with a majority particle size of 1500 micrometers. 2 Supplied per kilogram of diet: vitamin A, 7,937 IU; vitamin D, 2,646 IU; vitamin E, 19.8 IU; riboflavin, 5.3

mg; pantothenic acid, 9.3 mg; niacin, 39.7 mg; choline, 401 mg; vitamin B12, 10.6 µg; biotin, 66.0 µg; Mn,

79.4 mg; Fe, 33.1 mg; I, 1.0 mg; Cu, 5.3 mg; Zn, 66.1 mg; and Se, 180 µg. 3 All diets were analyzed in triplicate by the University of Missouri Agricultural Experimental Station

Chemical Laboratories (ESCL) (Columbia, MO).

54

Table 4-2. Mean body weight (BW, kg/bird) and body weight gain (BWG, kg/bd) 1,2

Treatment

d 28 BW (kg) d 35 BW (kg) d 28-35 BWG (kg)

PF 1.40 1.48c

0.08c

600µm 1.43 1.73ab

0.30a

900µm 1.42 1.74ab

0.32a

1200µm 1.48 1.81a

0.33a

1500µm 1.35 1.62bc

0.21b

SEM3

0.05 0.06 0.02

P-value 0.3336 0.0025 <0.0001 a-c

Means within the same column with no common superscript differ significantly (P ≤ 0.05). 1 N = 7 cage replicates/treatment where all corn treatments (600, 900, 1200, 1500 µm) birds n =

5, and PF birds n = 8. 2 Birds were fed a commercial corn-soy starter diet from day 0-21 and commercial grower from

day 21-28; birds were fed transitional diets from day 29 to 30 and were fed 100% treatment diets

from day 31-35. 3 SEM = Pooled standard error of the means.

55

Table 4-3. Mean ileal endogenous amino acid losses (g/100 g DM) collected from the terminal

end of the ileum1,2

Amino acid Current study Burley, 2014 Lemme et al., 20043

Aspartic Acid 0.14 0.05 -

Threonine 0.09 0.04 0.0571

Serine 0.08 0.04 -

Glutamic Acid 0.19 0.06 -

Proline 0.08 0.04 -

Glycine 0.07 0.03 -

Alanine 0.08 0.03 -

Cysteine 0.03 0.02 0.0169

Valine 0.11 0.04 0.0449

Methionine 0.03 0.01 0.0079

Isoleucine 0.07 0.02 0.0390

Leucine 0.12 0.04 0.0381

Tyrosine 0.05 0.02 -

Phenylalanine 0.07 0.02 0.0237

Lysine 0.12 0.02 0.0255

Histidine 0.03 0.01 0.0209

Arginine 0.09 0.03 0.0216

Total 1.45 0.52 0.2956 1 All endogenous loss values were calculated from protein free diet (PF).

2 Analysis was performed in triplicate by the University of Missouri Agricultural

Experimental Station Chemical Laboratories (ESCL) (Columbia, MO). 3 Original data from Lemme (2004): Values were converted from mg/kg DM to

g/100g DM.

56

Table 4-4. Apparent ileal AA digestibility (%)1

Diet

2

600 µm 900 µm 1200 µm 1500 µm SEM3

P-value

Aspartic Acid 72.15 75.73 76.31 75.31 6.01 0.1817

Threonine 59.04 65.40 65.48 65.26 6.95 0.0514

Serine 70.27 75.31 75.25 74.14 6.06 0.0706

Glutamic Acid 83.51 85.92 86.35 86.65 5.23 0.1431

Proline 78.74b

80.02b

77.29b

83.10a

4.95 0.0069

Glycine 66.26b

70.88a

72.78a

71.30a

6.04 0.0328

Alanine 81.91 83.55 84.60 85.06 5.13 0.1632

Cysteine 71.85 72.59 74.62 74.03 5.39 0.3697

Valine 64.83 68.76 70.61 70.05 6.48 0.0805

Methionine 82.17b

87.11a

86.60a

85.46a

5.71 0.0237

Isoleucine 71.95b

76.39a

77.86a

77.91a

6.34 0.0346

Leucine 83.51 85.34 85.95 86.90 5.19 0.1376

Tyrosine 78.92b

81.31ab

82.51a

83.31a

4.96 0.0425

Phenylalanine 78.24 81.90 81.57 82.28 6.52 0.1871

Lysine 72.08b

78.76ab

76.74a

76.03a

6.86 0.0464

Histidine 74.68 78.49 78.13 79.22 6.06 0.1281

Arginine 78.59 82.50 82.15 81.01 6.71 0.2212

Overall Mean 74.63 78.23 78.52 78.65 5.68 0.1175

1 Percentage data analyzed with arcsine transformation.

2 All values are the analyzed means of 3-5 replicates; 600 µm (4), 900 µm (5), 1200 µm (5), 1500

µm (4). 3 SEM = Pooled standard error of the means.

57

Figure 4-1. Apparent ileal AA digestibility (%, DM basis)

58

Table 4-5. True ileal AA digestibility (%)1

Diet

600µm 900µm 1200µm 1500µm SEM2

P-value

Aspartic Acid 100.18 102.08 103.23 102.36 1.31 0.4521

Threonine 95.20 97.37 99.71 99.41 1.67 0.2574

Serine 99.39 101.42 102.00 100.83 1.34 0.5795

Glutamic Acid 99.88 101.18 102.03 101.36 0.92 0.4536

Proline 93.74 94.64 94.74 96.46 1.00 0.3540

Glycine 92.28 94.80 95.10 95.16 1.38 0.4525

Alanine 98.25 99.09 100.02 100.00 0.94 0.5258

Cysteine 91.18 91.98 93.13 92.50 1.19 0.7054

Valine 97.04 99.32 100.86 100.23 1.50 0.3530

Methionine 102.41 104.50 105.98 104.35 1.04 0.1664

Isoleucine 100.08 102.37 103.85 103.50 1.36 0.2646

Leucine 98.85 99.95 100.84 100.60 0.91 0.4631

Tyrosine 98.09 100.54 101.24 101.07 0.97 0.1412

Phenylalanine 99.45 101.80 101.91 101.73 1.28 0.5111

Lysine 103.24 105.36 106.27 106.04 1.48 0.5078

Histidine 93.62 96.36 96.36 96.38 1.26 0.3765

Arginine 104.04 106.18 105.84 105.40 1.32 0.6985

Overall Mean3

98.05 99.94 100.77 100.43 1.19 0.4288



3 Overall means = mean of true digestibility values for 17 amino acids from each treatment diet.

59

Figure 4-2. True ileal AA digestibility (%, DM basis)

60

Table 4-6. True AA ileal digestibility (%) from literature EAAL values1

Diet

600 µm 900 µm 1200 µm 1500 µm SEM2

P-value

Threonine 81.94 85.65 87.16 86.89 1.67 0.1696

Cysteine 82.67 83.44 84.97 84.36 1.19 0.5545

Valine 80.07 83.22 84.93 84.33 1.50 0.1671

Methionine 87.23b

91.46a

91.44a

90.18ab

1.04 0.0434

Isoleucine 86.92 90.22 91.69 91.53 1.36 0.1054

Leucine 88.46 90.05 90.75 91.31 0.91 0.2153

Phenylalanine 85.48 88.69 88.52 88.92 1.28 0.2616

Lysine 78.73 84.44 83.04 82.44 1.48 0.0930

Histidine 86.38 89.54 89.40 89.83 1.26 0.2545

Arginine 85.04 88.50 88.15 87.19 1.32 0.3030

Overall Mean3

87.90 90.62 91.15 91.48 1.12 0.1671



3 Overall means = mean of true digestibility values for 10 amino acids from each treatment diet.

61

Figure 4-3. True ileal AA digestibility with literature EAAL values (%, DM basis)

62

Table 4-7. Jejunum digesta viscosity of male broilers at 35 days (cP)1,2

Treatment3

Viscosity (cP)1

PF 2.097c

600 µm 2.591ab

900 µm 2.727a

1200 µm 2.461b

1500 µm 2.500b

SEM4

0.08

P-value <0.0001 a-c

Means within the same column with no common superscript differ significantly (P ≤ 0.05). 1 cP = centipoises.

2 N = 7 cage replicates/treatment where all corn treatments (600, 900, 1200, 1500 µm) birds n =

5, and PF birds n = 8. 3 PF = Protein free diet; 600 = 600 µm ground corn; 900 = 900 µm ground corn; 1200 = 1200

µm ground corn; 1500 = 1500 µm ground corn. 4 SEM = Pooled standard error of the means.

63

Chapter 5 CORN PARTICLE SIZE EFFECTS IN PELLETED AND CRUMBLED

DIETS ON BROILER GROWTH PERFORMANCE AND CARCASS

CHARACTERISTICS

ABSTRACT

Particle size (PS) is an important contributing factor to broiler growth, feed intake and

conversion, as well as the amount of fines and pellet durability in complete commercial broiler

diets. Therefore, identification of an ideal corn PS to maximize bird growth performance and

carcass characteristics is desirable. Day old Cobb-500 straight run broiler chicks (1728) were fed

nutritionally complete commercial diets of one of four different corn PS (600 µm, 900 µm, 1200

µm, or 1500 µm) to 12 replicate pens of 36 birds in each and grown to 42 days of age. Birds were

fed crumbled starter from 0-18 d, pelleted grower from 18-32 d, and pelleted finisher from 32-42

d ad libitum.

Body weight (BW) was significantly greater at 18, 32, and 42 d among birds fed 600 µm

and significantly less among 1200 µm birds (2.89 vs. 2.80 kg at 42 d), while body weight gain

(BWG) was significantly greater from d 0-18 for 600 µm and 900 µm treatments and less for

1200 µm and 1500µm treatments. Overall BWG was also greater among 600 µm and less in 1200

µm fed birds (2.85 vs. 2.76 kg). Feed conversion ratio (FC) was poorer from d 0 – 18 for 1500

µm and less for 1200, 600, and 900 µm PS treatments. Overall FC was most efficient in the 1500

and 600 µm PS treatments (1.67), followed by 900 and 1200 µm PS (1.68 and 1.69, respectively).

There was no effect of PS on mortality or feed intake (FI) throughout the study. Gizzard weight

among males was significantly greater in the 600 µm compared to both 1200 and 900µm

treatments (35.88 vs. 30.73 and 30.29 g). Ceca weight among females was greatest in the 600 µm

64

PS treatment, and significantly less for 900, 1200, and 1500 µm PS Combined (male and female)

organ measurements revealed duodenum length to be significantly shorter in 900 µm birds and fat

pad was greater among 1500µm birds compared to all other treatments. In conclusion, smaller PS

treatments tended to have greater BW and BWG throughout production with more efficient FC

early in grow-out, while larger PS tended to have greater fat pad in male and pooled male and

female birds.

INTRODUCTION

Optimizing corn PS in a commercial setting for growth, development, and carcass

characteristics is invaluable to the poultry industry, as corn remains approximately 60% of a

standard commercial US poultry diet (Leeson and Summers, 1984). The availability of corn has

decreased in part due to greater ethanol production in the United States in recent years because

the majority of ethanol is made from corn. The amount of corn being used for ethanol has

increased to nearly 30% of all available US corn (Donohue and Cunningham, 2009). Between

2006 and 2007 the cost of corn increased 61% per bushel. These costs have decreased since but

still can effect on the poultry industry’s decisions, including the desire to hone in on the most

optimum corn PS. By doing so, feed mills will be able to utilize their time spend grinding corn

most effectively, and poultry producer’s feed costs will hopefully reflect these mill associated

costs with increased broiler growth performance and carcass characteristics. Feed costs are the

greatest cost for a broiler production, at nearly 70% (Donohue and Cunningham, 2009).

A concern for the poultry industry remains the desire for high quality pellets or crumbles,

as it is believed that more finely ground corn lends itself to more durable, higher quality pellets

with fewer fines. There is little historical work regarding corn PS both pre- and post-pelleting and

whether there are any bird performance effects due to changes in the pelleting process as most

65

studies focus on bird performance when fed a mash diet. However, a previous study in which

corn was ground using a hammer mill to a GMD of 679, 987, or 1289 µm reported the pellets

made with 1289 µm corn had higher pellet durability index (PDI) than more finely ground corn

while the birds fed either the 679 µm or 1289µm corn had higher BWG and FC than those fed

987 µm corn pelleted diets (Reece et al., 1986). Another study ground corn to a GMD of either

1343µm, using a roller mill, or 814 µm, using a hammer mill, and reported broilers fed the roller

mill corn performed equally or slightly better than those fed the hammer mill ground corn (814

µm), though both treatments performed equally when fed in a crumbled diet rather than a mash

diet (Reece et al., 1985). Both studies indicated that while there may be gains made with finer

corn PS, there is also great cost savings in more coarsely ground corn. That said, energy and

mechanical cost put forth by the feed mills could outweigh the benefits seen from finely ground

corn included into pelleted or crumbled diets, including a decreased hammer mill energy

consumption and increased production rate when grinding whole grains to coarser PS.

Poultry producers prefer to pellet or crumble broiler feeds rather than feed them in a

mash form as there’s an inherently greater FI for broilers with pelleted feed, and therefore a

greater BWG (Engberg et al., 2002). By pelleting, producers avoid broilers selectively choosing

larger particles of feed. While it’s already known that birds prefer larger particles to smaller ones

when selecting their feed, it was found that they do select finer particles at the end of a 24 hr

period once larger particles have disappeared (Portella et al., 1988). In situations where mash feed

is fed versus crumbled or pelleted feed, PS and selection is a greater concern, but also uniformity

of the feed ingredients is of high importance. For example, birds fed a mash diet of coarse (2010

µm), medium (897 µm), or fine (482 µm) hammer mill ground corn were found to have improved

performance when fed the medium ground corn, which also had the lowest geometric standard

deviation (GSD) when compared to the other treatments (Nir et al., 1994).

66


Birds and Housing

Straight run Cobb-500 broiler chicks (1728) were acquired from a local hatchery and

placed in 48 pens with 36 birds per pen at a stocking density of 0.07m2. Birds were given feed

and water ad libitum while photoperiod began at 23:1 hours L:D and decreased to 18:6 hours

L:D by 7 days of age and continued until 28 days of age, following the Cobb-500 broiler

management guide (Cobb-Vantress, 2012). At 28 days, lighting increased to 20:4 L:D and

remained until 42 days of age. Brooding temperature began at 32.2°C at day 0 of the study, and

was gradually decreased to 21°C by 14 days of age. Birds were fed standard commercial corn-soy

based diets and from d 0 -18, first as a crumbled commercial broiler starter, then from d 18-32

birds were fed a pelleted commercial grower diet, and from d 32- 42 birds were given a pelleted

commercial finisher diet which met all bird nutrition requirements and provided one of the four

corn PS treatments (600, 900, 1200, or 1500 µm) (Wenger Feeds, LLC, Rheems, PA). All diets

were analyzed on an as-is basis (Table 5-1). Corn was ground using a hammer mill to a geometric

mean diameter (GMD) of 600, 900, 1200, or 1500 µm, respectively. The study and bird handling

procedures involved were approved by The Pennsylvania State University Institutional Animal

Care and Use Committee (#47085). At placement and days 18, 32, and 42 BW and FI were

measured on a pen basis and FC, BW and BWG were calculated on a per bird basis, and then

averaged by treatment.

At d 42, after weighing all birds and calculating the mean BW and standard deviation for

each pen, the pen closest to the overall mean for each treatment was selected and 10 males and 10

females were randomly selected for processing to determine carcass parts and yield

measurements. Birds were electrically stunned and exsanguinated, followed by soft-scalding and

67

batch de-feathering. Evisceration and parting of birds were done by hand by the same two

individuals for standardization. All carcasses were parted out into boneless, skinless breasts,

while wings, thighs, and drums had left skin on. Shell (backbone, ribcage and breast skin) and

abdominal fat pad were also weighed. All carcass parts were weighed individually and later used

for dressing percentage determination.


Data was analyzed with a one-way ANOVA using the GLM procedure of SAS software

version 9.4 (SAS Institute, 2013) and values were deemed significant if P ≤ 0.05. When

significant differences between treatments were identified Tukey’s test was used for multiple

mean comparisons. All percentage data had an arcsine transformation applied before analysis



The nutrient profile of the corn (Delivery 2) utilized for the study herein is described

further in Table 3-5, with all corn treatments (600, 900, 1200, and 1500 µm) ground pre-pelleting.

Proximate analyses, including crude protein (CP), ether extract (EE), crude fiber (CF), dry matter

(DM), and ash for all treatment diets as shown in Table 5-1.

The floor-pen broiler study yielded no significantly different chick weights at placement,

but at day 18, the 600 and 900 µm treatments were significantly heavier than the 1200 and 1500

µm birds (Table 5-2). At day 32 and 42, 600 µm treatment birds were heavier than 1200 µm birds

(P < 0.05) and the 900 and 1500 µm birds were intermediate and did not differ from the 600 and

1200 µm treatments. Body weight gain (BWG) from day 0-18 showed birds fed the 600 and 900

68

µm treatment diets being heavier than 1200 and 1500 µm (P < 0.05). There were no significant

differences between treatments from day 18-32 or 32-42, but overall, 600 µm birds gain was

significantly greater than 1200 µm treatment birds and the 900 and 1500 µm treatments were

intermediate and non-significant (Table 5-3). Throughout the study there were no significant

differences between treatments in feed intake (Table 5-4). Feed conversion (FC) from day 0-18

was significantly better for 600 and 900 µm, poorer for 1200 µm birds, and poorest for the 1500

µm birds (P < 0.0001). Overall FC was significant, with 600 and 1500 µm having the best

conversion (Table 5-5). Previous reports have indicated that PS can be maintained through

pelleting (Nir et al., 1995), and growth performance on crumbled starter (Reece et al., 1986) and

pelleted grower diets utilizing two grinds of wheat (either 300 or 955 µm geometric mean

diameter) (Péron et al., 2005) indicated broilers perform equally with no negative performance

effects as a result of utilizing a greater PS. Percent mortality was not different between

treatments throughout the study (Table 5-6).

After processing, female broilers had no significant treatment differences between bled

weight, skinless breasts, thighs (skin on), drums (skin on), wings, shell with breast skin,

abdominal fat pad, or carcass (Table 5-7), and no differences in processing weights expressed as a

percent of carcass weight (Table 5-8). Male processing weights yielded no differences between

treatments except for abdominal fat pad, where the 900 µm and 1500 µm were significantly

greater than the 1200 µm treatment birds (Table 5-9). Male processing weights expressed as a

percent of carcass weight yielded no differences except for drums (skin on) and abdominal fat

pad. Drums of birds fed the 900 µm treatment were significantly smaller than birds fed the 1200

µm treatment diets and the fat pad of 1200 µm was less than the 1500 µm treatment (Table 5-10).

For the combined carcass weights of both males and females, birds fed the 1500µm diet had

significantly greater abdominal fat pads than those fed 1200µm feed, and no other significant

differences were seen between treatments (Table 5-11). Lastly, the combined broiler mean

69

processing weights expressed as a percent of carcass weight showed no differences between

treatments in the parameters measured (Table 5-12).

The digestive tract organs were also measured, and female ceca weight of the 600 µm

treatment was significantly greater than all other treatments (15.73 vs. 11.12, 13.12, 12.86 g) but

no other significant differences were observed (Table 5-13). Male broiler digestive tract

measurements showed no differences except in empty gizzard weights, where the 600 µm was

significantly heavier than 900 and 1200 µm treatment birds (35.88 vs. 30.29 and 30.73 g) and the

1500 µm birds were intermediate and nonsignificant compared to the other treatments (Table 5-

14). Previous work has found conflicting results on gastrointestinal length relative to feeding

differing PS diets. Amerah et al. (2007) found all digestive tract segments to be longer in broilers

fed a mash diet with finely ground corn compared to coarse ground corn. But when the same diets

were pelleted, no significant differences in digestive organ length were ascertained. Another

study reported greater duodenum lengths but no differences in duodenum weight in broilers fed

whole wheat particles included into pelleted diets (Taylor and Jones, 2004). Multiple studies have

shown gizzard and small intestine segment lengths to be decreased when broilers were fed

pelleted or crumbled diets, rather than mash diets (Nir et al., 1995; Engberg et al., 2002).While

neither male or female birds herein revealed any differences in gastrointestinal tract lengths,

combined (male and female) broiler digestive tract weights and lengths showed duodenum length

(cm) in the 900 µm treatment birds was significantly shorter than 600, 1200, and 1500 µm

treatment birds (25.96 vs. 27.74, 27.82, and 27.77 cm) (Table 5-15). Lastly, combined male and

female bird results showed differences between treatments for duodenum length (cm), with the

900 µm treatment birds being significantly shorter than all other treatments. This would indicate

there is no clear impact of dietary corn PS on gastrointestinal organ weights or lengths herein.

Energy costs related to grinding the corn used in the current study was reported in Table

3-1 and showing a clear linear trend of energy usage as PS decreases. Energy cost, as well as time

70

spent grinding corn decreased linearly as PS increased, and throughput (tonnes/hr) through the

hammer mill (TPH) was also greater. Historically, grinding feed ingredients to their desired PS is

the second most expensive operation, after the cost of pelleting (Reece et al., 1985). By reducing

energy cost and minimizing time spent grinding corn particles, reduced milling costs could be

realized while maintaining current standards for broiler growth performance and carcass

characteristics.

In conclusion, BW and BWG of floor raised broilers were greater for birds fed smaller

particle size treatments throughout the study and overall. While FC was also better from smallest

PS treatments from day 0-18, these differences became muted over time with the overall results.

No differences were seen in female carcass weights or percent of carcass, and the only difference

seen in males and in combined carcass weight and percent of carcass weight data between

treatments were the abdominal fat pad, where 1200 µm was significantly smaller in 1500 µm

treatment birds. Broiler producers and feed mills in the US could find savings by increasing the

GMD particle size of corn included into broiler pelleted and crumbled diets with less machine

energy and greater TPH. However, broiler BW and BWG from placement through 18 d of age

benefitted from the 600 and 900 µm PS treatment corn. This small amount feed, ~18% of the

total feed a 42 day old broiler would consume, might be worth incurring the greater milling costs,

while the grower and finisher phases from 18 – 42 d of age did not reveal a clear advantage or

impact of corn PS that would warrant greater milling expenses for smaller PS.

ACKNOWLEDGEMENTS

This study was funded through the 2015 Pennsylvania Poultry Industry Broiler Research

Check-off Program.

71

REFERENCES



455.

Cobb-Vantress. 2012. Cobb 500 Broiler Performance & Nutrition Supplement Guide. Available

at http://www.cobb-vantress.com/docs/default-source/cobb-500-

guides/Cobb500_Broiler_Performance_And_Nutrition_Supplement.pdf (verified 2 October

2016).










Nir, I., G. Shefet, and Y. Aaroni. 1994. Effect of particle size on performance: 1. Corn. Poult. Sci.

73:45–49.






72



Sci. 64:1834–1839.

Reece, F. N., B. D. Lott, and J. W. Deaton. 1986. Effects of environmental temperature and corn

particle size on response of broilers to pelleted feed. 65:636–641.




Taylor, R. D., and G. P. D. Jones. 2004. The incorporation of whole grain into pelleted broiler

chicken diets. II. Gastrointestinal and digesta characteristics. Br. Poult. Sci. 45:237–246.

73

Table 5-1. Proximate analysis of completed broiler feed (%)1

Phase Treatment DM EE CP CF Ash

Starter 600 µm 88.86 3.88 21.70 2.80 4.71

900 µm 88.29 3.64 21.65 2.53 4.82

1200 µm 88.38 3.45 20.85 2.57 4.83

1500 µm 89.79 3.98 19.56 2.67 4.72

Grower 600 µm 89.49 3.87 19.70 2.27 4.95

900 µm 87.89 3.59 19.47 2.37 4.62

1200 µm 88.51 3.49 19.27 2.37 4.21

1500 µm 88.87 3.60 19.03 2.60 4.93

Finisher 600 µm 88.33 5.65 18.13 2.97 3.62

900 µm 88.43 5.53 18.40 2.87 4.29

1200 µm 88.18 5.79 18.74 2.87 4.46

1500 µm 90.61 6.80 18.69 2.87 4.20

1 All samples analyzed in triplicate (Barrow-Agee Laboratory, Memphis, TN).

74

Table 5-2. Floor-pen broiler body weight (BW, kg/bd)

Treatment n d 01 d 18 d 32 d 42

600 µm 12 0.43 0.69a

1.88a

2.89a

900 µm 12 0.43 0.69a

1.87ab

2.84ab

1200 µm 12 0.43 0.65b

1.81b

2.80b

1500 µm 12 0.43 0.64b

1.84ab

2.87ab

SEM1

- 0.08 0.01 0.01 0.01

P-value - 0.8774 <0.0001 0.0106 0.0280 a-b

Means within the same column with no common superscript differ significantly (P ≤ 0.05). 1 SEM = Pooled standard error of the means.

75

Table 5-3. Floor-pen broiler body weight gain (BWG, kg/bd)

Treatment n d 0-18 d 18-32 d 32-42 Overall

600 µm 12 0.65a

1.19 1.00 2.85a

900 µm 12 0.64a

1.18 0.98 2.80ab

1200 µm 12 0.61b

1.16 1.00 2.76b

1500 µm 12 0.60b

1.20 1.03 2.83ab

SEM1

- 0.01 0.01 0.01 0.01

P-value - <0.0001 0.1572 0.2492 0.0282 a-b


76

Table 5-4. Floor-pen broiler feed intake (FI, kg feed/bd)


600 µm 12 0.86 1.96 1.94 4.75

900 µm 12 0.85 1.97 1.89 4.70

1200 µm 12 0.84 1.94 1.89 4.66

1500 µm 12 0.85 1.96 1.93 4.72

SEM1

- 0.01 0.01 0.01 0.02

P-value - 0.3729 0.7139 0.2196 0.1725 a-b


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Table 5-5. Floor-pen broiler feed conversion (FC, kg feed/kg BWG)


600 µm 12 1.32c

1.64 1.93 1.67c

900 µm 12 1.32c

1.65 1.94 1.68b

1200 µm 12 1.39b

1.66 1.91 1.69a

1500 µm 12 1.42a

1.62 1.87 1.67c

SEM1

- 0.007 0.008 0.012 0.003

P-value - <0.0001 0.2711 0.1668 0.0451 a-b


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Table 5-6. Floor-pen broiler percent mortality and culls (%)1

Treatment n d 0-18 d 18-322

d 32-42 Overall

600 µm 12 2.20 3.22 2.60 8.02

900 µm 12 1.44 1.21 2.00 4.65

1200 µm 12 2.42 1.23 1.24 4.89

1500 µm 12 1.93 2.74 3.15 7.82

P-value - 0.7385 0.1000 0.4254 0.1463 a-b

Means within the same column with no common superscript differ significantly (P ≤ 0.05). 1 Percentage data analyzed using an arcsine transformation.

2 Birds culled due to bad legs were increased at 32 d of age.

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Table 5-7. Floor-pen broiler female mean processing weights (g)1

Treatment n Bled

weight

Skinless

breasts

Thighs

(skin on)

Drums

(skin on) Wings

Shell with

breast skin

Abdominal

fat pad Carcass

600 µm 10 2566.7 659.7 326.9 244.8 193.5 558.8 38.9 1983.7

900 µm 10 2567.8 635.4 329.2 251.7 205.5 569.5 40.2 1991.3

1200 µm 10 2494.6 623.8 324.8 247.4 201.4 533.4 40.1 1930.7

1500 µm 10 2543.7 641.2 324.2 246.7 196.6 551.8 46.6 1960.5

P-value - 0.8862 0.8667 0.9886 0.9461 0.5849 0.4704 0.4318 0.9107 1 N = 10 females from each treatment (600, 900, 1200 or 1500 µm).

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Table 5-8. Floor-pen broiler female mean processing weights as a percent of carcass weight at 42d1,2

(%)

Treatment n Carcass yield3

Breasts Thighs

(skin on)

Drums

(skin on) Wings

Shell with

breast skin

Abdominal

fat pad

600 µm 10 77.15 33.09 16.48 12.37 9.83 28.23 1.99

900 µm 10 77.47 31.70 16.59 12.64 10.37 28.69 2.02

1200 µm 10 77.37 32.22 16.82 12.84 10.44 27.67 2.08

1500 µm 10 77.05 32.69 16.54 12.59 10.04 28.15 2.36

P-value - 0.9450 0.6252 0.7680 0.5493 0.3785 0.3080 0.4373 1 Percentage data analyzed using an arcsine transformation.

2 N = 10 females from each treatment (600, 900, 1200 or 1500 µm).

3 Carcass yield (%) calculated as 100 x carcass weight (g) / bled weight (g).

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Table 5-9. Floor-pen broiler male mean processing weights (g)1

Treatment n Bled

weight

Skinless

breasts

Thighs

(skin on)

Drums

(skin on) Wings

Shell with

breast skin

Abdominal

fat pad Carcass

600 µm 10 3007.2 732.9 394.3 303.4 238.7 642.4 39.4ab

2311.8

900 µm 10 3004.5 775.1 394.3 298.3 238.6 640.7 45.5a

2346.9

1200 µm 10 2881.6 701.3 385.8 307.5 226.5 593.6 31.1b

2214.7

1500 µm 10 2994.3 714.0 404.8 299.4 240.7 660.1 45.5a

2318.9

P-value - 0.2555 0.1088 0.6703 0.7721 0.1545 0.1094 0.0125 0.2094 a-b

Means within the same column with no common superscript differ significantly (P ≤ 0.05). 1 N = 10 males from each treatment (600, 900, 1200 or 1500 µm).

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Table 5-10. Floor-pen broiler male mean processing weights as a percent of carcass weight at 42d (%)1,2

Treatment n Carcass

yield3 Breasts

Thighs

(skin on)

Drums

(skin on) Wings

Shell with

breast skin

Abdominal

fat pad

600 µm 10 76.88 31.67 17.05 13.13ab

10.34 27.82 1.70ab

900 µm 10 78.13 33.02 16.79 12.71b

10.17 27.31 1.93ab

1200 µm 10 76.86 31.64 17.46 13.96a

10.26 26.69 1.41b

1500 µm 10 77.42 30.78 17.43 12.94ab

10.38 28.46 1.97a

P-value - 0.6153 0.1040 0.3911 0.0432 0.8395 0.2782 0.0302 a-b

Means within the same column with no common superscript differ significantly (P ≤ 0.05). 1 Percentage data analyzed using an arcsine transformation.

2 N = 10 males from each treatment (600, 900, 1200 or 1500 µm).


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Table 5-11. Floor-pen broiler combined male and female mean processing weights (g)1

Treatment n Bled

weight

Skinless

breasts

Thighs

(skin on)

Drums

(skin on) Wings

Shell with

breast skin

Abdominal

fat pad Carcass

600 µm 20 2787.0 696.3 360.6 274.1 216.1 600.6 39.1ab

2147.8

900 µm 20 2786.2 705.3 361.7 275.0 222.0 605.1 42.8ab

2169.1

1200 µm 20 2688.1 662.5 355.3 277.4 213.9 563.5 35.6b

2072.7

1500 µm 20 2769.0 677.6 364.5 273.0 218.6 606.0 46.1a

2139.7

P-value - 0.6767 0.4936 0.9459 0.9839 0.7873 0.1728 0.0223 0.6243 a-b

Means within the same column with no common superscript differ significantly (P ≤ 0.05). 1 N = 10 males and 10 females from each treatment (600, 900, 1200 or 1500 µm).

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Table 5-12. Floor-pen broiler combined male and female mean processing weights as a percent of carcass weight at 42d (%)1,2

Treatment n Carcass

yield3 Breasts

Thighs

(skin on)

Drums

(skin on) Wings

Shell with

breast skin

Abdominal

fat pad

600 µm 20 77.02 32.38 16.76 12.75 10.08 28.03 1.84

900 µm 20 77.80 32.36 16.69 12.68 10.27 28.00 1.97

1200 µm 20 77.12 31.93 17.14 13.40 10.35 27.18 1.75

1500 µm 20 77.24 31.73 16.99 12.76 10.21 28.30 2.17

P-value - 0.6327 0.7605 0.4053 0.0544 0.6747 0.1826 0.0697 1 Percentage data analyzed using an arcsine transformation.

2 N = 10 males and 10 females from each treatment (600, 900, 1200 or 1500 µm).


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Table 5-13. Floor-pen broiler female organ weights (g) and lengths (cm)1,2

Treatment Liver

(g)

Gizzard

(g)

Proventriculus

(g)

Duodenum,

pancreas (g)

Jejunum

(g)

Ileum

(g)

Total small

intestine (g)

Duodenum

(cm)

Jejunum

(cm)

Ileum

(cm)

Total small

intestine

(cm)

Ceca

(g)

600 µm 43.42 28.59 8.87 14.26 19.86 17.22 51.34 27.76 74.32 72.68 174.76 15.73a

900 µm 43.52 29.07 7.38 13.46 18.14 17.13 48.73 25.42 64.18 72.82 162.42 11.12b

1200 µm 41.17 30.16 7.19 13.42 17.84 16.08 47.34 27.73 72.41 73.30 173.44 13.12b

1500 µm 46.44 30.52 6.96 14.32 19.23 18.22 51.77 28.14 68.48 71.11 167.73 12.86b

P-value 0.1873 0.5141 0.0903 0.4358 0.2676 0.3690 0.2152 0.0803 0.2965 0.9138 0.4189 0.0033

a-b Means within the same column with no common superscript differ significantly (P ≤ 0.05). 1 All organs were weighed empty, after removing all digesta contents by gentle squeezing and/or cutting open. 2 N = 10 females from each treatment (600, 900, 1200 or 1500 µm).

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Table 5-14. Floor-pen broiler male organ weights (g) and lengths (cm)1,2

Treatment Liver

(g)

Gizzard

(g)

Proventriculus

(g)

Duodenum,

pancreas (g)

Jejunum

(g)

Ileum

(g)

Total small

intestine

(g)

Duodenum

(cm)

Jejunum

(cm)

Ileum

(cm)

Total small

intestine

(cm)

Ceca

(g)

600 µm 48.87 35.88a 8.64 14.74 21.09 19.03 54.86 27.71 77.09 77.69 182.49 16.28

900 µm 48.27 30.29b 7.85 15.09 21.25 18.49 54.83 26.49 71.62 76.07 174.18 16.53

1200 µm 47.42 30.73b 8.09 14.33 20.50 18.13 52.96 27.91 72.20 76.11 176.22 16.74

1500 µm 50.74 34.17ab 8.51 14.62 20.24 18.95 53.81 27.40 72.45 76.85 176.70 16.10

P-value 0.6514 0.0404 0.6086 0.7411 0.7531 0.8820 0.8418 0.3209 0.1067 0.9421 0.3524 0.9909 a-b Means within the same column with no common superscript differ significantly (P ≤ 0.05). 1 All organs were weighed empty, after removing all digesta contents by gentle squeezing and/or cutting open. 2 N = 10 males from each treatment (600, 900, 1200 or 1500 µm).

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Table 5-15. Floor-pen broiler combined organ weights (g) and lengths (cm)1,2

Treatment Liver

(g)

Gizzard

(g)

Proventriculus

(g)

Duodenum,

pancreas (g)

Jejunum

(g)

Ileum

(g)

Total small

intestine

(g)

Duodenum

(cm)

Jejunum

(cm)

Ileum

(cm)

Total small

intestine

(cm)

Ceca

(g)

600 µm 46.14 32.24 8.76 14.50 20.48 18.13 53.10 27.74a 75.71 75.19 178.63 16.01

900 µm 45.90 29.68 7.92 14.28 19.70 17.81 51.78 25.96b 67.90 74.45 168.30 13.83

1200 µm 44.30 30.45 7.64 13.88 19.17 17.11 50.15 27.82a 72.31 74.71 174.83 14.93

1500 µm 48.59 32.34 7.69 14.47 19.74 18.59 52.79 27.77a 70.47 73.98 172.21 14.48

P-value 0.1783 0.1772 0.0937 0.5936 0.4879 0.4020 0.3727 0.0181 0.0843 0.9602 0.1861 0.4072

a-b Means within the same column with no common superscript differ significantly (P ≤ 0.05). 1 All organs were weighed empty, after removing all digesta contents by gentle squeezing and/or cutting open. 2 N = 10 males and 10 females from each treatment (600, 900, 1200 or 1500 µm).

88

Chapter 6 EFFECTS OF CORN PARTICLE SIZE ON PULLET GROWTH

PERFORMANCE AND REPRODUCTIVE TRACT DEVELOPMENT

ABSTRACT

The current study was conducted to evaluate how laying hen pullets growth performance

is affected by one of three differing corn particle sizes (600, 900, or 1500 µm) included into

nutrient balanced, complete pullet diets. Research with broilers would suggest dietary particle

size (PS) is important, though little information is available regarding the impact on pullet growth

or performance. Day old Hy-Line W-36 chicks (325) were placed 25 birds per cage and fed

isonitrogenous, isocaloric mash diets with 600 µm, 900 µm, or 1500 µm treatment corn. Body

weight (BW) and body weight gain (BWG) were measured at placement and weeks 5, 10, 16,

and 17. Feed intake (FI) and feed conversion (FC) were calculated at each time point. Among the

pullets there was a significant trend for the birds fed the 600 µm mash treatment diet to be heavier

than birds fed the 900 µm or 1500 µm treatment diets at week 5, 10, 16, and trending towards the

same at 17 weeks of age (P = 0.0521). Pullet BWG reflected BW from placement to week 5,

pullets fed the 600 µm treatment gained significantly more than the 900 and 1500 µm treatments,

though the significance disappeared between 5-10 weeks and 10-16 weeks of age, the same trend

linear trend continued and by 16 – 17 weeks BWG of 600 µm fed birds was greater numerically

than the 900 and 1500 µm fed pullets (P = 0.0541). There were no differences in feed intake,

conversion, or mortality. This study indicated finely milled corn (600 µm) was more beneficial to

89

optimum pullet growth and reproductive development leading to successful hen performance,

while larger PS could reduce pullet BW, delay fleshing, and overall growth performance.

INTRODUCTION

Little research has been conducted specifically looking at how corn PS affects pullet growth

performance before entering into the laying hen stage of life. Light weight pullets at 18 weeks of

age have been reported to consume less feed, reach sexual maturity later, lay smaller eggs and lay

less egg mass by 70 weeks of age than a heavier pullets (Leeson et al., 1997). Recently, a study

by Frikha et al. (2011) evaluated brown egg laying pullets fed either corn or wheat (at 50% of

their diet) ground through a 6-, 8-, or 10-mm screen and found finely ground corn (929 µm

geometric mean diameter) was significantly better than greater corn PS (991 µm and 1042 µm

GMD) and all wheat treatments (967, 1119, 1216 µm) were better than corn for pullet BWG and

FC from placement through 6 weeks of age.

The Hy-Line's W-36 commercial manamgent guide (2016) recommends pullets be fed a

crumbled starter and later have a range of PS with 25% less than 1000 µm, 65% between 1000-

2000 µm and 10% between 2000-3000 µm for the grower phase, and increasing the PS to include

35% between 1000-2000 µm and 2000-3000 µm plus 5% of particles greater than 3000 µm for

both developer diets and into production. Hy-Line’s PS recommendations for pullets vary widely,

by over 1000 µm. Portella et al. (1988) reported more uniform feed is less selectively chosen for

larger particles by birds.

In growing broilers, Nir et al. (1994a) reported chickens fed mash diets, with greater

uniformity, spent less time a bird spent looking for and ultimately choosing larger particles. Bird

90

PS selection increases with age and as mouth gape increases (Morgan and Heywang, 1941; Nir et

al., 1994b). Weanling pigs fed pelleted diets based on ground corn, hard endosperm sorghum, or

soft endosperm sorghum found 6% better FC and 23% better BWG among corn fed piglets than

either sorghum based diet (Healy et al., 1994) and concluded PS to be most influential for the first

two weeks of life, with the smallest particles (300 µm) being most beneficial for piglet growth,

and greater PS selection was observed as pigs age.


Birds and Housing

Day old Hy-Line W-36 chicks (325) were acquired from Hy-Line USA (Elizabethtown,

PA), and randomly placed into 13 pullet cages, with 25 birds per cage, at 142 cm2 per bird. There

were three corn particle size treatments with 4 replicate cages for each of the 600 and 1500 µm

corn and 5 replicate cages of the 900 µm corn treatment diet. Management practices followed the

Hy-Line management guide for the W-36 pullets, with a dark grow to dark lay program created

for 41N latitude following Hy-Line’s lighting guide (Hy-Line, 2016). All feed and water were

provided ad libitum throughout the entire study. At 10 days of age, all birds were hot blade beak

trimmed to avoid feather picking or cannibalism later in life. At five weeks of age, each cage of

birds was weighed, separated into two cages of 12-13 birds per cage, at 284 cm2 per bird and feed

intake and feed conversion were calculated (600 and 1500 µm treatments had 8 replicate cages

each and the 900 µm treatment had 10 replicate cages). Birds were fed a standard phase fed

dietary program with the same energy and nutrient levels in all diets with only GMD of corn

91

varying as the treatment (600, 900, or 1500 µm). Birds were fed a starter diets from 1-5 weeks of

age (Appendix A.1), grower diets from 5-10 weeks of age (Appendix A.2), developer diets from

10-17 weeks of age (Appendix A.3), and pre-lay diets from 17-19 weeks of age (Appendix A.4).

At each diet change, birds were weighed and feed intake was measured. All study procedures and

methods for this study were approved by The Pennsylvania State University Institutional Animal

Care and Use Committee (IACUC Protocol #46838).

Body Weight, Growth Performance, and Organ Measurements

Birds were weighed as a cage group at placement, 5, 10, 16, and 17 weeks of age. From

these weights, BWG from placement through 5 weeks, 5 – 10 weeks, 10 – 16 weeks, and 16 – 17

weeks was calculated. At these same time points, feed intake was measured as g/bd/d. At 16

weeks of age (one week before lighting was increased to 13:11 L:D from 12:12 L:D), 6 pullets

per treatment were randomly selected and euthanized to evaluate growth and reproductive

development utilizing the Hy-Line (0-3) breast score (Hy-Line, 2016). Gastrointestinal organ

weights (g) were measured for the gizzard, proventriculus, and small intestine (duodenum, ileum,

and jejunum), ceca, and lengths (cm) were measured for the small intestine sections.

Additionally, the ovary was weighed and examined to quantify differences between treatments in

reproductive maturation, such as larger ovary cortical weight by 16 weeks of age.

92


Data was analyzed with a one-way ANOVA using the MIXED procedure of SAS 9.4

(SAS Institute, 2013). Means were deemed significant when P ≤ 0.05. Tukey’s test was used for

multiple mean comparisons when significant differences were determined between treatments



At placement, there were no differences between pullet chick body weights (P = 0.3524).

Later at 5, 10, and 16 weeks of age, pullet BW was significantly higher for the finest PS treatment

(600 µm), intermediate for 900µm, and was lowest for the 1500 µm PS and trended the same at

17 weeks of age (P < 0.10) (Table 6-1). At 5 weeks of age, pullets were between 2 – 20 g of the

goal weight (Hy-Line, 2016), and at 10 weeks of age, all treatment birds were 50 – 80 g less than

the Hy-Line management guide. However, by 16 weeks of age the 600 µm treatment fed pullets

reached the Hy-Line guide goal. The 900 µm treatment pullets reached the Hy-Line set goal at 17

weeks, but the 1500 µm birds were still 32 g below. Body weight gain (BWG) was significant

from 0-5 weeks of age, with birds fed 600 µm gaining the most weight, compared to 900 and

1500 µm treatments (279.87 vs. 269.36 and 258.16 g) though from 16 – 17 weeks of age, the 600

µm bird BWG was significantly less compared to the 900 and 1500 µm treatment birds (53.84 vs.

77.62 and 75.36 g) (Table 6-1). Previous work by Leeson et al. (1997) evaluated four strains of

Leghorn pullets (Babcock, DeKalb, H & N, and Shaver) fed either standard (19.5%) or low levels

(16.5%) of protein through 18 weeks of age and found regardless of strain, pullets with lighter

93

BW matured more slowly (P < 0.01) and produced less egg mass (P < 0.05) through 70 weeks of

age.

Pullet FI (Table 6-2) did not significantly differ between treatments from placement to 17

weeks of age. Compared to the Hy-Line management guide (2016), pullets fed the 900 and 1500

µm corn treatment diets ate slightly less than the standard for 0 – 5 weeks of age, while the 600

µm treatment birds ate slightly more. Frikha et al. (2011) evaluated pullets fed wheat or corn

passed through a 6-, 8-, or 10-mm hammer mill screen and found from 0 – 45 days of age birds

fed finer PS, regardless of cereal type, had significantly greater BWG and better FC compared to

those fed greater PS cereal grains. From 5 – 10 weeks of age, all corn treatment pullets had

comparable FI to the Hy-Line standard for that age (44.84 g/bd/d). Again, all treatment (600, 900,

and 1500 µm) pullets had comparable FI (54.29 g/bd/d average across treatments) from 10 – 16

weeks of age to the calculated Hy-Line W-36 average for the same time frame at 56.25 g/bd/day.

From 16-17 weeks of age, both the 600 and 900 µm PS treatment birds ate less than the Hy-Line

guidelines for the same timeframe (0 – 17 weeks of age) with the exception of birds fed 1500 µm

treatment corn diets, which ate more and were likely in part due to the 1500 µm birds

compensating for lower BW (5, 10 and 16 weeks of age) with greater intake, whereas 600 µm fed

pullets were able to consume and utilize the nutrients and able to reach the Hy-Line W-36 BW

goal for pullets more quickly. Overall, pullets fed the 600 µm treatment feed ate an average of

48.95 g/bd/day, where the 900 and 1500 µm treatments ate an average of 49.46 and 50.92

g/bd/day. Other research has found the need for finer PS in diets for animals in the growth phase

of life. For example, weanling pigs were found to have benefitted from a finer particle size during

the first two weeks post weaning and optimum PS increased with age (Healy et al., 1994).

94

Pullet FC (Table 6-3) was not significantly different between treatments (600, 900, or

1500 µm) from placement to 5 weeks of age, 5 – 10, or 10 – 16 weeks of age (P < 0.10).

Comparing these time periods to the averaged Hy-Line W-36 FC indicates the treatment pullets

herein grew more efficiently from 0 – 5 weeks of age. From placement thorough 5 weeks of age

all treatment birds had a FC ratio under the 3.13 Hy-Line average at 2.99, 3.07, and 3.11 for the

600, 900, and 1500 µm treatments, respectively. From 5 – 10 weeks of age treatment birds had a

FC ratio of 3.82, 3.79, and 3.84 (600, 900, and 1500 µm, respectively). From 10 – 16 weeks of

age all treatment diets had better FC ratios than the Hy-Line guide (5.63). From 16 – 17 weeks of

age FC was significantly higher for the 600 µm birds compared to the 900 µm birds (7.43 vs. 5.66

g feed/g gain), where the 1500 µm treatment birds were an intermediate value with a FC of 6.57

and all treatments were greater compared to the Hy-Line management guide estimate of 4.36,

possibly due to feed wastage from small feed troughs at that time. Lastly, FC as a time weighted

average over 17 weeks for the 900 and 1500 µm corn treatments were more efficient throughout

the study compared to the 600 µm treatment (4.46 and 4.71 vs. 5.10 g feed/g gain).

At 16 weeks of age pullets showed no significant differences in organ weights, including

gizzard, proventriculus, small intestine segments, ceca, fat pad, or ovary (Table 6-4). The ovary

was examined to establish a baseline of ovary and follicle condition of each dietary treatment

before increasing lighting and stimulating lay. There were no significant differences between

ovary weights nor were there pre-selection follicles large enough to weigh separately.

Furthermore, the weights and lengths of the gastrointestinal tract showed no differences between

treatments. Interestingly, at 16 weeks of age the 600 µm fed pullets had greater breast scores and

fleshing at a score of 2.00 where the 900 and 1500 µm pullets had scores of 1.30 and 1.20,

respectively. Breast score is an indication of fleshing and birds with a higher score are more in

95

line with degree of maturity and readiness to enter the hen house. Ovary weight showed no

significant difference but numerically greater ovary weight was associated with smaller PS (600

µm) and greater PS treatment pullets had reduced ovary size (900 and 1500 µm).

The current study revealed pullets could benefit from feeding finer corn PS, such as 600

µm. Pullet live performance was found to have the greatest benefit from the 600 µm PS treatment

at 5, 10, and 16 weeks of age leading in BW and BWG compared to the other PS treatments.

Pullets fed the 600 µm treatment diet reached Hy-Line W-36 commercial laying hen target BW

more quickly (16 weeks of age) than did the 900 µm treatment birds, which took until 17 weeks

of age and the 1500 µm treatment birds never reached target weight by 17 weeks of age. Pullets

fed the 600 µm treatment diets had greater fleshing by 16 weeks of age compared to the other

treatments, and while there were no follicles present for enumeration, there was a numerical trend

indicating the 600 µm treatment fed pullets had greater cortical ovary mas than the 900 or 1500

µm treatments. However, from a feed milling perspective, smaller particle sizes are a financial

burden as there is a linear trend towards greater cost/tonne ($) and milling time as particle size is

made smaller. Additionally, throughput (tonnes/hour) is reduced as particle size decreases, so

corn is less efficient to grind. The pullet study herein showed birds have a better start and better

BW and BWG up through 16 weeks of age when fed the 600 µm treatment corn and it may be

worth incurring the cost of extra milling to benefit pullet growth performance and reproductive

maturation by 17 weeks of age.

96

ACKNOWLEDGEMENTS

This study was funded through the 2015 Pennsylvania Poultry Industry Egg Research

Check-off Program.

REFERENCES

Frikha, M., H. M. Safaa, M. P. Serrano, E. Jiménez-Moreno, R. Lázaro, and G. G. Mateos. 2011.

Influence of the main cereal in the diet and particle size of the cereal on productive

performance and digestive traits of brown-egg laying pullets. Anim. Feed. Sci. Tech.

164:106–115.

Healy, B. J., G. A. Kennedy, P. J. Bramel-Cox, K. C. Behnkes, R. H. Hines, and J. D. Hancock.


Sci. 72:2227–2236.







Nir, I., R. Hillel, G. Shefet, and Z. Nitsan. 1994a. Effect of grain particle size on performance. 2.


Nir, I., G. Shefet, and Y. Aaroni. 1994b. Effect of particle size on performance. 1. Corn. Poult.

Sci. 73:45–49.

97



SAS Institute. 2013. SAS User’s Guide. Version 9.4. SAS Inst. Inc., Cary, NC.



98

Table 6-1. Pullet body weight (BW, g/bird) and body weight gain (BWG, g/bird) 1,2

BW BWG

Treatment d 0 wk 5 wk 10 wk 16 wk 17

d 0 – wk 5 wk 5 - 10 wk 10 - 16 wk 16 – 17

600 µm 38.38 318a

740a

1188a

1242 280a

421 449 53.84b

900 µm 37.96 307b

721b

1160ab

1238 269b

413 440 77.62a

1500 µm 38.36 297c

705c

1140b

1198 258c

408 435 75.36a

SEM3

0.23 2.41 5.30 9.01 12.98 2.41 4.45 6.65 5.93

P-value 0.3524 <0.0001 0.0007 0.0047 0.0521 <0.0001 0.1447 0.3804 0.0166 a-c

Means within the same column with no common superscript differ significantly (P ≤ 0.05). 1 Placement – 5 weeks: 600 and 1500 µm, N = 4 cages; 900 µm, N = 5 cages (25 birds/cage for all treatments).

2 5 – 17 weeks: 600 and 1500 µm, N = 8 cages; 900 µm, N = 10 cages (11-13 birds/cage for all treatments).

3 SEM = Pooled standard error of the means.

99

Table 6-2. Pullet feed intake (FI, g/bird/day)1,2

Treatment d 0 – wk 5 wk 5 –10 wk 10 – 16 wk 16 – 17

Average3

600 µm 24.06 45.98 54.08 58.66

48.95

900 µm 23.53 44.66 54.18 61.45

49.46

1500 µm 23.13 44.72 54.60 65.66

50.92

SEM4

0.69 1.28 0.67 2.51 1.60

P-value 0.6679 0.7219 0.8540 0.2312 0.6996

Hy-Line

Guide5 23.70 44.84 56.25 61.50 44.11

a-b Means within the same column with no common superscript differ significantly (P ≤

0.05).

1 Placement – 5 weeks: 600 and 1500 µm, N = 4 cages each; 900 µm, N = 5 cages (25

birds/cage for all treatments). 2 5 – 17 weeks: 600 and 1500 µm, N = 8 cages each; 900 µm, N = 10 cages (12-13

birds/cage for all treatments). 3 Time weighted average for 17 week old pullets.


5 All values averaged from Hy-Line W-36 commercial management guide by week and

averages of both low and high ends of given estimates (2016).

100

Table 6-3. Pullet feed conversion (FC, g feed/g gain)1,2

Treatment d 0 – wk 5 wk 5 –10 wk 10 – 16 wk 16 – 173

Overall4

600 µm 2.99 3.82 5.07 7.43a

5.10

900 µm 3.07 3.79 5.18 5.66b

4.49

1500 µm 3.11 3.84 5.28 6.57ab

4.71

SEM5

0.09 0.12 0.07 0.45 0.17

P-value 0.6980 0.9424 0.1861 0.0312 0.0695

Hy-Line

Guide6

3.13 3.41 5.63 4.35 4.41

a-b Means within the same column with no common superscript differ significantly (P ≤ 0.05).

1 Placement – 5 weeks: 600 and 1500 µm, N = 4 cages; 900 µm, N = 5 cages (25 birds/cage for

all treatments). 2 5 – 17 weeks: 600 and 1500 µm, N = 8 cages; 900 µm, N = 10 cages (12-13 birds/cage for all

treatments). 3 At 16 -17 weeks, 600 and 1500 µm, N = 7 cages; 900 µm, N = 10 cages (12-13 birds/cage for

all treatments). 4 Time weighted average for 17 week old pullets.


6 All values averaged from Hy-Line W-36 commercial management guide by week and

averages of both low and high ends of given estimates (2016).

101

Table 6-4. Pullet organ weights and lengths (16 weeks)1

Trt Breast

score

Gizzard

(g)

Provent-

riculus

(g)

Duodenum,

pancreas

(g)

Jejunum

(g)

Ileum

(g)

Total

small

intestine

(g)

Duodenum

length (cm)

Jejunum

length

(cm)

Ileum

length

(cm)

Total

length

(cm)

Ceca

(g)

Cortical

ovary

(g)

Fat

pad

(g)

600 µm 2.00a 28.28 4.55 7.68 9.77 9.42 26.87 20.47 36.42 42.25 102.13 7.30 0.48 18.92

900 µm 1.30b 26.50 4.38 7.33 9.33 8.58 25.25 20.70 42.35 39.68 102.73 6.25 0.45 22.52

1500 µm 1.20b 29.57 5.13 7.97 9.06 9.23 24.75 23.03 47.55 44.80 115.38 6.80 0.43 16.35

SEM 0.16 1.13 0.25 0.31 0.53 0.73 1.30 1.02 3.42 1.61 4.39 0.37 0.03 3.77

P-value 0.0042 0.1902 0.1115 0.3746 0.6557 0.7046 0.5013 0.1775 0.1033 0.0503 0.0857 0.1720 0.3811 0.5244 a-b

Means within the same column with no common superscript differ significantly (P ≤ 0.05).

1 600 µm, N = 6 birds; 900 µm, N = 3 birds; 1500 µm, N = 6 birds.

102

Chapter 7

EFFECT OF CORN PARTICLE SIZE ON HEN PERFORMANCE, EGG

QUALITY AND ECONOMICS

ABSTRACT

This laying hen study continued evaluating corn particle size (PS) fed in isocaloric mash

diets at one of four sizes (600, 900, 1200, or 1500 µm) from 19 – 43 weeks of age. At 19 weeks

of age, 108 Hy-Line W-36 pullets (27 per treatment) were moved to the hen house with 4

replicate groups of two cages with 6 birds per treatment and an additional single cage containing

3 birds, for a total of 9 replicate cages per treatment. Hens were weighed at placement and every

period (23, 27, 31, 35, 39, and 43 weeks of age), along with feed intake (FI) and feed conversion

(FC) in kg feed/kg egg weight, and kg feed/dozen eggs was calculated. At the end of each 28 d

period, eggs were weighed and at alternating periods either egg proportions (percent shell,

albumen, and yolk) or egg quality (albumen height, Haugh units, meat or blood spot enumeration,

and yolk color) measurements were performed. A small sample of hens was euthanized and

gastrointestinal organ weights and lengths were measured and the number of preovulatory

follicles was enumerated at 19, 31, and 43 weeks of age. While there were no significant

differences found in egg production, eggs per 28 d period, hen body weight (BW), FI, FC, or egg

proportions, hens fed the 600 µm diets were found to have significantly lighter yolk color than

900, 1200, or 1500 µm treatment fed birds at 35 and 43 weeks of age, and overall. Visual

examination of the 600 µm treatment corn had less yellow color compared to the 900, 1200, and

1500 µm corn treatments. Perhaps greater surface area and exposure led to oxidation of the

xanthophyll pigments contained in the seed coat. Hens at 19 weeks of age fed the 600 and 1500

103

µm treatment diets had heavier fat pads than the 900 µm treatments (34.38, 32.38 vs. 21.10g; P =

0.0002). At 31 weeks of age, organ measurements indicated the 600 and 1200 µm fed birds ileum

weights were significantly heavier than the 900 µm treatment (16.13, 15.67 vs. 11.88g) and

overall small intestine weight of the 1200 µm birds was significantly heavier than the 900 µm

(41.25 vs. 34.85g). As a percent of body weight at 31 weeks of age, ileum and proventriculus

from the 600 µm treatment birds were found to be significantly heavier than either the 900 or

1500 µm, but none of these results repeated themselves at 43 weeks of age. Based on the results

from the current study, hens fed corn with greater PS in a mash diet performed equally in all

parameters to hens fed finely ground corn with the only exception that yolk color was decreased

when feeding 600 µm corn compared to the other treatments.

INTRODUCTION

Corn remains the most common energy ingredient used for commercial poultry in the US,

at 60% of a standard commercial poultry diet (Leeson and Summers, 1984), and grinding of

ingredients is the greatest single energy expense in creating mash feed for laying hens (Deaton et

al., 1988). Feed is the greatest cost in poultry production, and taking extra steps to reduce PS

further for a mash layer diet increases energy consumption and decreases throughput (TPH)

resulting in greater production costs at the feed mill. Reducing energy expenditures in laying hen

feed manufacture could greatly benefit the US poultry industry if there is no loss in hen

performance or production by doing so. Little research has focused directly on laying hen PS

preference and whether one PS over another benefits percent egg production or results in higher

egg weights earlier in life. A study by Portella et al. (1988) comparing hen PS preference in mash

or crumbed diets found FI was not different between these treatments. Researchers also found FI

104

increased in hens fed mash diets when more finely ground corn particles were fed and decreased

when feed was changed quickly to a larger PS. Laying hens (Portella et al., 1988) and broilers

(Nir et al., 1994a) have been found to prefer larger particles when given the choice, so a more

uniform diet is beneficial as birds can less easily take time looking for the larger particles to

consume because ingredient selection can result in altered nutrient consumption.

Deaton et al. (1988) fed laying hens mash diets including corn ground either by roller

mill or hammer mill, where roller mill corn ranged from 1,343 – 1,501 µm and hammer mill

ground corn ranged from 814 – 873 µm. They found these PS did not influence laying hen

percent egg production, BW, egg weight, FI, FC, eggshell breaking strength or percent mortality.

Pelleting diets for laying hens has also been studied, and determined the process of pelleting

improved laying hen nutrient uptake, reduces feed wastage and reduces energy spend eating or

choosing feed (Morgan and Heywang, 1941).

Work on pullets has shown pullets with lighter BW at 18 weeks of age consumed less

feed overall and reached sexual maturity later in life, with lighter weight eggs by 70 weeks of age

compared to heavier pullets (Leeson et al., 1997). Other pullet work (Leeson et al., 1997) focused

on four strains (Babcock, DeKalb, H & N, and Shaver) of Leghorn pullets and evaluated pullet,

then later, hen performance by feeding either a low protein diet (16.5% CP) enriched with Lys

and Met + Cys, or a conventional hen diet (19.5% CP) in mash form and found only minor

differences between strains for pullets and through early lay, with very little long-term effect on

laying performance.

105


Birds and Housing

At 19 weeks of age (108) Hy-Line W-36 pullets were transferred to hen housing with

stacked cages and manure belts at Penn State’s Poultry Education Research Center. All treatments

birds were housed with 3 hens per cage and there were 4 replicate groups (2 cages/group) and one

lone cage per treatment for a total of 27 birds/treatment. Hy-Line’s management guide for W-36

hens followed the dark grow to dark lay lighting program (Hy-Line, 2016) which was continued

from the birds’ time as pullets. Feed and water were given ad libitum through the length of the

study, and all birds were fed the same nutritional profile. Phase 1 hen diets (Appendix B.1 and

Appendix B.2) were fed from 19 to 36 weeks of age and through period 4, at which time Phase 2

hen diets (Appendix B.3) began from 36 to 43 weeks of age during periods 5 and 6.

Treatment Diet Formulation

Hen diets were formulated to be isocaloric for all phases, and included 53.15% ground

corn for phase 1 (periods 1 and 2), 54.38% ground corn for phase 1 (periods 3 and 4), and 61.76%

ground corn for phase 2 (periods 5 and 6) hen diets. Phase 1, period 1 and 2 only included

granulated limestone, where Phase 1, period 2 and 3 treatments included 50:50 granulated

limestone:Ca chips. All diets included mono-dicalcium phosphate as feed P and as another dietary

source of calcium.

106

Data Collection

Body Weight and Production Data

All hens were individually wing banded as they were housed in their hen cages at 19

weeks of age, and weighed individually at the end of every 28 d period. Feed intake and

conversation (feed/dozen eggs and kg feed/kg eggs) were calculated on an average bird basis

within a replicate group of cages (2 cages of 3 birds each for a total N = 6 birds per replicate

group).

Egg Production & Quality Parameters

The numbers of eggs laid per cage were recorded daily and sample eggs were collected

and labeled the second to last day of a given period, refrigerated and stored for 24 h and then

analyzed. Age at first egg was measured and analyzed. At the conclusion of periods 1, 3, and 5

egg proportions (percent of egg yolk, albumen, or shell) were measured. Albumen height, Haugh

units, yolk color, and any meat or blood spots were enumerated at the conclusion of period 2, 4,

and 6. Albumen height was measured (in mm) using a digital QCD and QCH albumen height

gauge (TSS York, York, England), and Haugh units were calculated using egg albumen height

and individual egg weight, where Haugh unit is a measure of albumen quality. Yolk color was

measured with a Roche yolk color fan by one individual throughout the study. When yolk color

was determined the incidence of blood or meat spots were also recorded. Blood and meat spots

can result from ruptured blood vessels during ovulation or from sloughed epithelial cells from the

hen’s reproductive tract.

107

Gastrointestinal Tract Measurements and Preovulatory Follicle Determination

A sample of young hens from each treatment of the preceding pullet study fed 600, 900,

or 1500 µm corn treatments were euthanized at 19 weeks of age for gastrointestinal tract and

follicle measurements, whereas all other hens that continued into the hen house were fed 900 µm

the corn as pullets to keep flock uniformity at the beginning of the hen study. At peak lay (31

weeks), and at the conclusion of the study when hens were 43 weeks of age, hens from all four

treatment diets, were randomly selected and euthanized for gastrointestinal tract and follicle

measurements (600 µm n = 15, 900 µm n = 12, and 1500 µm n = 15). All birds were weighed and

the gastrointestinal tract organs and intestine segments were weighed (g) and measured (cm).

Additionally, ovary and preovulatory follicle weights were measured, and preovulatory follicles

were enumerated. All data was analyzed by weight also expressed as a percentage of bird BW,

save enumeration of preovulatory follicles and lengths (cm) of small intestine sections.

Preovulatory follicles are defined as the rapid growth phase of ovarian follicles. They

were selected based on maturity; specifically color and size, as preovulatory follicles to document

reproductive status. Recruited follicles lowest on the pre-ovulatory hierarchy were distinguished

from the other follicles which had not been recruited, by relatively larger size, yellow color, and

increased vasculature. This is based on the theory that as a yolk is released from the ovary, a

signal is sent to the ovary to recruit another follicle to take its place in the hierarchy (Johnson,

2015).

108


Data was analyzed using with a one-way ANOVA using the MIXED procedure of SAS

9.4 (SAS Institute, 2013) and percentage data was analyzed with an arcsine transformation.

Means were deemed significance at P ≤ 0.05 and differences between treatments were identified

using Tukey’s test for multiple mean comparisons when necessary (Steel and Torrie, 1960).


Mean hen day egg production was calculated (Table 7-1) along with mean eggs per hen

housed for each 28 d period (Table 7-2). All hens peaked in percent egg production at the end of

period 2, at 27 weeks of age, with percent production peaking at 97.26%, 96.07%, 94.52%, and

96.19% for 600, 900, 1200 and 1500 µm fed birds, respectively. There were no significant

differences between treatments at any time point or overall hen day egg production. Age at first

egg was also recorded but no significant differences were seen between treatments, because all

hens came into lay within three days of each other (data not shown).

Birds were weighed every period (Table 7-3) and although there were no significant

differences between treatments throughout the study, all treatment hens remained within the Hy-

Line W-36 management guide (2016) BW targets for period 1 and 2, though they exceeded the

target BW for the remainder of the study (periods 3 – 6).

Egg weight was measured at the conclusion of each 28-d period (Table 7-4) and no

significant differences were seen as a result of the corn PS treatments. Treatment eggs all reached

large size (at least 57 g) by the end of period 4, at 35 weeks of age, while the Hy-Line W-36

guide suggests average egg weight should reach 57.1 g by 26 weeks of age.

109

Feed intake was measured at the conclusion of each 28-d period and calculated on a per

bird/day basis (Table 7-5), though no differences were seen between treatments throughout the

study. Additionally, mean feed conversion as kg feed consumed per dozen eggs (Table 7-6) and

kg feed consumed/kg eggs produced per bird (Table 7-7) were calculated, but no differences were

seen between treatments. Deaton et al. (1988) found similar results by feeding laying hens mash

diets including either roller mill (1,343 – 1,501µm GMD) or hammer mill (814 – 873µm GMD)

corn and determined this range in PS did not influence laying hen percent egg production, BW,

egg weight, FI, FC, eggshell breaking strength or percent mortality.

Egg quality was measured every other period, and is shown in Table 7-8. Though there

were no significant differences between treatments at 27 weeks of age for any parameters

measured (albumen height in mm, Haugh units, numbers of meat or blood spots, or yolk color), at

35 and 43 weeks of age, yolk color was significantly reduced (P < 0.0001) by the 600 µm

treatment compared to all others. At 35 weeks of age, yolk color was measured as 6.69 vs. 7.65,

7.88, and 7.67 (600 vs. 900, 1200, and 1500 µm). The 43 week and overall means for yolk color

followed this same trend, and while there is no explanation for this coloring difference, the same

person measured yolk color for all dates measured and therefore do not suspect an intra-observer

bias to be an issue with these data. Egg proportions (percent shell, albumen, and yolk) were also

measured and no significant differences resulted from these measurements (Appendix B.4).

A sample of hens from each treatment was euthanized at 19, 31, and 44 weeks of age for

reproductive tract and gastrointestinal tract measurements. While all pullets entering the study

were fed 900 µm corn to ensure uniformity, a random sample of 600 and 1500 µm corn fed

pullets were kept through 19 weeks for organ weights, lengths, and preovulatory and follicle

evaluation. At 19 weeks of age no differences were seen in organ weight or length as a result of

corn PS treatments except for fat pad, where 600 µm and 1500 µm fed hens were significantly

110

greater than 900 µm (34.38 and 32.38 vs. 21.10g). There were no preovulatory follicles present

among any of the treatments at 19 weeks of age for enumeration; therefore only cortical ovary

was weighed. At 31 weeks of age (Table 7-10), there were no significant differences seen

between treatments for any gastrointestinal organ lengths, ovary weight, or number of

preovulatory follicles. There were differences between ileum weight, with the 600 and 1200 µm

treatments being significantly heavier than the 900 µm treatment (16.13 and 15.67 vs. 11.88 g)

and in overall small intestine weight, with the 1200 µm treatment being significantly heavier than

the 900 and 1500 µm (41.25 vs. 34.85 and 35.57 g), however none of these results repeated

themselves at 43 weeks of age and all parameters were nonsignificant (Appendix B.5).

Organ weight measurements were also analyzed as a percent of bird BW at 31 and 43

weeks of age. Though there were no differences seen between treatments for most parameters at

31 weeks (Table 7-11), the percent ileum and proventriculus weight, for the 600 µm treatment

was significantly greater than either the 900 or 1500 µm, but these results were not repeated at 43

weeks of age (Appendix B.6) and no differences between treatments in any parameters were seen.

Greater length and overall digestive tract development has been thought to be influenced by

dietary particle size, with coarser particles slowing the rate of passage through the digestive tract,

allowing for more exposure to digestive enzymes, which can break down the particles more

thoroughly and possibly improve nutrient digestibility and utilization (Carré, 2000). Any

gastrointestinal tract results became muted by the end of the study at 43 weeks of age, with

nonsignificant differences between treatments. However, previous work indicated that feeding

fine mash diets can cause hypertrophy of the small intestine (Nir et al., 1994b), and more coarsely

ground particles result in lower duodenal weights (Nir et al., 1995).

While hen performance was not impacted, birds fed 600 µm PS corn had lighter color

yolks than other treatments at 31, and 43 weeks of age but no differences were seen in albumen

111

height, Haugh units, and blood or meat spots. The outer layers of the corn kernel, especially the

seed coat, contribute the grand majority of the xanthophylls to a diet from corn (Corke, 2016).

Visual examination of the ground corn treatments indicated the 600 µm grind had less yellow

color than the 900, 1200, and 1500 µm treatments. Perhaps the greater surface area and exposure

led to oxidation of these seed coat pigments. Hens showed no significance in egg production, or

number of eggs per bird per period, BW, feed conversion (both kg feed/kg eggs and kg

feed/dozen eggs) related to dietary corn PS treatments. Safaa et al. (2009) ground dent corn or

Durum wheat to pass through either a 6-, 8-, or 10-mm screen on a hammer mill, where the

ground corn GMDs were 774, 922, or 1165 µm and ground wheat GMDs were 998, 1111, or

1250 µm and fed to Lohmann Brown hens from 20 to 48 weeks of age. These authors reported

there were no significant differences between grain type, or coarseness of grind, for all production

and egg quality parameters measured. Hamilton and Proudfoot (1995) fed ground wheat (coarse

or finely ground) to White Leghorn hens and reported hen BW, egg production, and FC were not

significantly impacted by PS treatments throughout the study.

Where Hy-Line (2016) recommends hens in production to have feed consisting of 25%

particles less than 1,000 µm, 35% of particles between 1,000 – 2,000 µm, 35% of particles

between 2,000 – 3,000 µm and 5% of particles greater than 3,000 µm, the current study revealed

finer particles to minimally impact layer performance. These findings suggest that although

younger pullets can benefit from finer corn PS through 17 weeks of age, larger particle sizes

(1200 or 1500 µm) are satisfactory once birds are in the hen house, and no further milling to finer

PS (600 or 900 µm) is necessary.

112

ACKNOWLEDGEMENTS

This study was funded through the 2015 Pennsylvania Poultry Industry Egg Research

Check-off Program.

REFERENCES

Carré, B. 2000. Effets de la taille des particules alimentaires sur les processus digestifs chez les

oiseaux d’élevage. INRA Prod. Anim. 13:131–136.

Corke, H. 2016. Grain: Morphology of Internal Structure. Pages 41–50 in Encyclopedia of Food

Grains. Wrigley, C.W., Corke, H., Seetharaman, K., Faubion, J., eds. 2nd ed. Academic

Press, Kidlington, Oxford, England.

Deaton, J. W., B. D. Lott, and J. D. Simmons. 1988. Hammer mill versus roller mill grinding of

corn for commercial egg layers. Poult. Sci. 1:1342–1344.

Hamilton, R. M. G., and F. G. Proudfoot. 1995. Effects of ingredient particle size and feed form

on the performance of Leghorn hens. Can. J. Anim. Sci. 75:109–114.



Johnson, A. L. 2015. Ovarian follicle selection and granulosa cell differentiation. Poult. Sci.

94:781-785.



Leeson, S., and J. D. Summers. 1984. Influence of nutritional modification on skeletal size of

Leghorn and broiler breeder pullets. Poult. Sci. 63:1222–1228.

113





Nir, I., R. Hillel, G. Shefet, and Z. Nitsan. 1994a. Effect of grain particle size on performance. 2.


Nir, I., G. Shefet, and Y. Aaroni. 1994b. Effect of particle size on performance. 1. Corn. Poult.

Sci. 73:45–49.



Safaa, H. M., E. Jimenez-Moreno, D. G. Valencia, M. Frikha, M. P. Serrano, and G. G. Mateos.

2009. Effect of main cereal of the diet and particle size of the cereal on productive

performance and egg quality of brown egg-laying hens in early phase of production. Poult.

Sci. 88:608–614.

SAS Institute. 2013. SAS User’s Guide. Version 9.4. SAS Inst. Inc., Cary, NC.



114

Table 7-1. Mean hen day egg production (%) by dietary treatment1

Hen Age (wk) 23 27 31 35 39 43 Average

Period 1 2 3 4 5 6

600 µm 59.29 97.26 94.64 97.02 95.24 93.30 89.91

900 µm 59.17 96.07 93.93 96.13 95.39 92.86 89.29

1200 µm 56.79 94.52 91.67 95.98 94.05 93.01 88.22

1500 µm 58.81 96.19 95.60 97.02 94.64 93.60 89.48

SEM 0.04 0.01 0.01 0.01 0.01 0.01 0.80

P-value 0.9625 0.3113 0.2628 0.7860 0.6991 0.9534 0.5141 1 Period 1-3: N = 5 replicates for all treatments. Period 4-6: N = 4 replicates for all

treatments.

115

Table 7-2. Mean eggs per period (28d) per hen housed by dietary treatment1


Period 1 2 3 4 5 6

600 µm 16.60 27.23 26.50 27.17 26.67 26.13 25.17

900 µm 16.57 26.90 26.30 26.92 26.71 26.00 25.00

1200 µm 15.90 26.47 25.67 26.88 26.33 26.04 24.70

1500 µm 16.47 26.93 26.77 27.25 26.50 26.21 25.07

SEM 1.09 0.28 0.38 0.31 0.23 0.29 0.23

P-value 0.9645 0.3081 0.2440 0.7823 0.6666 0.9588 0.5180 1 Period 1-3: N = 5 replicates for all treatments. Period 4-6: N = 4 replicates for all

treatments.

116

Table 7-3. Hen body weight (BW, kg)


Period 1 2 3 4 5 6

600 µm 1.46 1.54 1.57 1.62 1.62 1.58 1.53

900 µm 1.44 1.52 1.55 1.62 1.63 1.61 1.53

1200 µm 1.48 1.54 1.62 1.64 1.63 1.61 1.54

1500 µm 1.49 1.54 1.58 1.60 1.63 1.63 1.54

SEM 0.02 0.02 0.02 0.02 0.02 0.02 0.02

P-value 0.2420 0.8323 0.2391 0.6423 0.9967 0.2741 0.9645

117

Table 7-4. Egg weights (g)


Period 1 2 3 4 5 6

600 µm 50.32 54.49 55.99 57.08 56.84 56.73 55.71

900 µm 49.46 54.13 55.85 57.38 56.98 56.58 55.42

1200 µm 51.44 53.82 56.41 58.14 56.73 58.02 56.00

1500 µm 51.08 53.69 56.91 57.02 57.10 56.98 55.86

SEM 0.96 0.56 0.54 0.69 0.69 0.56 0.29

P-value 0.4498 0.7515 0.5229 0.6503 0.9845 0.2807 0.5444

118

Table 7-5. Feed intake (g/hen/day)1


Period 1 2 3 4 5 6

600 µm 74.35 91.43 94.11 99.85 103.57 101.12 103.36

900 µm 74.58 90.71 93.93 101.86 105.43 103.05 103.92

1200 µm 75.12 90.71 95.00 103.87 104.69 103.65 104.64

1500 µm 73.27 92.56 93.15 101.41 109.08 99.93 104.33

SEM 1.30 0.81 5.23 3.97 2.25 1.33 1.51

P-value 0.7861 0.3538 0.4932 0.9120 0.3801 0.2298 0.9383 1 Period 1-3: N = 5 replicates for all treatments. Period 4-6: N = 4 replicates for all treatments.

119

Table 7-6. Feed conversion (kg feed/dozen eggs)1


Period 1 2 3 4 5 6

600 µm 1.54 1.13 1.07 1.23 1.31 1.30 1.27

900 µm 1.54 1.13 1.20 1.27 1.33 1.33 1.30

1200 µm 1.61 1.15 1.24 1.30 1.34 1.34 1.31

1500 µm 1.51 1.15 1.17 1.25 1.38 1.28 1.29

SEM 0.09 0.01 0.07 0.05 0.03 0.02 0.02


120

Table 7-7. Feed conversion (kg feed/kg eggs)1


Period 1 2 3 4 5 6

600 µm 2.54 1.73 1.76 1.56 1.66 1.68 1.80

900 µm 2.60 1.74 2.16 1.59 1.68 1.71 1.85

1200 µm 2.60 1.78 2.21 1.60 1.70 1.68 1.84

1500 µm 2.46 1.79 2.05 1.59 1.76 1.64 1.82

SEM 0.15 0.02 0.32 0.20 0.22 0.24 0.11


121

Table 7-8. Egg quality

Hen age (wk) 27

Albumen height (mm) HU Blood spots Meat spots Yolk color

600 µm 9.97 100.13 0.00 0.05 7.41

900 µm 9.50 97.61 0.00 0.03 7.32

1200 µm 9.52 98.25 0.00 0.18 7.38

1500 µm 9.62 98.77 0.00 0.08 7.42

SEM1

0.19 0.96 - 0.06 0.13

P-value 0.2506 0.2987 - 0.2382 0.9499

Hen age (wk) 35

600 µm 9.74 98.48 0.03 0.03 6.69b

900 µm 9.87 98.98 0.00 0.04 7.65a

1200 µm 9.62 97.79 0.00 0.00 7.88a

1500 µm 9.57 97.80 0.07 0.00 7.67a

SEM1

0.21 0.93 0.03 0.02 0.11

P-value 0.7526 0.7766 0.3465 0.5714 <0.0001

Hen age (wk) 43

600 µm 9.20 96.00 0.00 0.07 6.55b

900 µm 9.28 96.07 0.00 0.03 7.29a

1200 µm 8.94 94.44 0.00 0.17 7.53a

1500 µm 8.75 93.48 0.08 0.14 7.35a

SEM1

0.22 1.25 0.05 0.09 0.09

P-value 0.2942 0.3632 0.4923 0.7134 <0.0001

Hen age (wk) Average

600 µm 9.67 98.37 0.01 0.05 6.93b

900 µm 9.52 97.43 0.00 0.03 7.40a

1200 µm 9.35 96.88 0.00 0.13 7.56a

1500 µm 9.29 96.57 0.05 0.08 7.47a

SEM1

0.12 0.64 0.02 0.04 0.07

P-value 0.1180 0.2025 0.1577 0.3204 <0.0001

a-b Means within the same column with no common superscript differ significantly (P ≤ 0.05).


122

Table 7-9. Pullet organ weights and lengths (19 weeks)1

Trt Breast

score

Mouth

lesions

Tongue

lesions Gizzard (g)

Proventriculus

(g) Ceca (g) Ovary (g) Fat pad (g)

600 µm 1.17 0.00 0.00 30.25 5.68 7.05 1.22 34.38a

900 µm 1.00 0.00 0.00 26.90 5.10 7.07 0.93 21.10b

1500 µm 1.33 0.00 0.00 29.43 4.62 7.47 1.03 32.38a

SEM2

0.20 0.00 0.00 1.40 0.42 0.61 0.24 2.74

P-value 0.5414 - - 0.3200 0.1722 0.8415 0.7108 0.0200

Trt

Duodenum,

pancreas

(g)

Jejunum

(g)

Ileum

(g)

Small intestine

(g)

Duodenum

(cm)

Jejunum

(cm)

Ileum

(cm)

Small intestine

(cm)

600 µm 9.63 13.83 14.10 37.56 23.22 45.30 46.40 114.92

900 µm 8.97 11.77 11.27 32.00 23.03 43.30 40.70 107.03

1500 µm 9.65 12.28 13.76 35.69 25.48 43.45 46.28 115.22

SEM2

0.70 0.96 1.34 3.09 1.97 1.84 1.82 4.21

P-value 0.7900 0.3058 0.3704 0.4262 0.3682 0.6683 0.1244 0.4157 a-c

Means within the same column with no common superscript differ significantly (P ≤ 0.05). 1 600 µm, N = 6 birds; 900 µm, N = 3 birds; 1500 µm, N = 6 birds.


123

Table 7-10. Hen organ weights and lengths (31 weeks)1

Trt BW

(kg)

Gizzard

(g)

Proventriculus

(g)

Pancreas,

duodenum (g) ceca (g) Fat pad (g)

Ovary +

follicles

(g)

# Preovulatory

follicles

Pre-

ovulatory

follicles (g)

600 µm 1.60 28.55 9.67 11.22 10.48 40.52

48.30

6.50 40.40

900 µm 1.55 26.22 7.35 9.88 12.25 43.75

43.51

6.17 36.03

1200 µm 1.68 32.83 9.00 11.87 11.48 53.27

45.54

6.33 38.20

1500 µm 1.64 32.75 8.78 10.97 9.63 35.13

48.42

6.50 42.67

SEM2

2.78 2.57 0.62 0.50 0.79 5.52 3.09 0.31 3.21

P-value 0.6231 0.2167 0.0907 0.0726 0.1350 0.1617 0.6308 0.8437 0.5140

Trt Jejunum

(g)

Ileum

(g)

Small intestine

(g)

Duodenum

(cm)

Jejunum

(cm)

Ileum

(cm)

Small

intestine

(cm)

600 µm 13.23 16.13a 40.58

ab 28.08 54.95 58.30 141.33

900 µm 13.08 11.88b 34.85

c 26.10 51.02 54.73 131.85

1200 µm 13.72 15.67a 41.25

a 27.40 58.75 60.01 146.17

1500 µm 11.25 13.35ab

35.57bc

27.78 52.87 55.68 136.33

SEM2

0.94 0.96 1.86 1.28 2.67 2.13 4.50

P-value 0.2920 0.0164 0.0467 0.7084 0.2343 0.3077 0.1630 a-c

Means within the same column with no common superscript differ significantly (P ≤ 0.05). 1 N = 6 birds/treatment.


124

Table 7-11. Hen organ weights as a percent of BW (%) (31 weeks)

1,2

Treatment Gizzard Proventriculus Pancreas,

duodenum Jejunum Ileum

Total small

intestine Ovary Fat pad

600µm 1.79 0.60a

0.70 0.82 1.01a

2.54 3.00 2.54

900µm 1.70 0.40b

0.64 0.85 0.77b

2.26 2.82 2.83

1200µm 1.97 0.54ab

0.70 0.82 0.94ab

2.48 2.71 3.09

1500µm 1.97 0.53b

0.67 0.69 0.81b

2.17 2.96 2.15

SEM3

0.14 0.02 0.04 0.05 0.06 0.12 0.16 0.28

P-value 0.3857 0.0054 0.3797 0.1792 0.0460 0.1064 0.6388 0.1554 1 Percentage data analyzed using an arcsine transformation.

2 N = 6 birds/treatment.


a-c Means within the same column with no common superscript differ significantly (P ≤ 0.05).

125

Chapter 8

CONCLUSIONS AND FUTURE WORK

Based on the studies conducted herein, corn particle size (PS) can greatly affect feed mill

energy usage, bird nutrient uptake and digestibility, and growth performance. Generally, smaller

PS (600 or 900 µm corn) are more beneficial to chick growth and later performance in

commercial phases, specifically, 0 – 18 d for broilers and 0 – 17 weeks for pullets. As birds

mature and reach some threshold of critical size and age, PS doesn’t affect performance

significantly, and the reduced milling inputs necessary to grind corn to either 1200 or 1500 µm, in

concert with the lack of a clear benefit to feeding finer PS after 18 d of age for broilers and 17

weeks of age for young layers substantiates the practice. The studies conducted aimed to

document potential benefits and downfalls of varying corn PS in broiler, pullet and layer diets.

Nutrient concentration differences between Delivery 1 and Delivery 2 corn were minimal. Rather,

the greatest differences between treatments in Delivery 1 and Delivery 2 resulted from

differences in screen size, amperage, and power used between deliveries causing small variations

in the corn PS percent separations. Despite minor energy differences incurred by the hammer

mills between the two deliveries, the trend was consistent between Delivery 1 and Delivery 2 that

greater PS treatments had greater throughput in tonnes/hr, and linearly less cost and time spent

grinding corn to the desired PS.

Jejunum viscosity results from the broiler digestibility study indicated the 600 and 900

µm treatment diets were the most viscous compared to the 1200 and 1500 µm treatment diets,

suggesting the smaller PS treatments would have decreased digesta flow. These results were

corroborated by apparent and true ileal digestibility values showing the 600 µm treatment had

126

significantly reduced amino acid (Met, Lys, Ile, Pro, Tyr, and Gly) digestibility. Body weight and

body weight gain of broilers fed the treatment diets (600, 900, 1200, or 1500 µm) were found to

be greater for the 1200 µm birds compared to the PF and 1500 µm treatments, though the

decreased body weight and body weight gain seen in the 1500 µm treatment birds may be

explained by the young broilers’ inability to consume the largest particles in the diet. The broiler

floor pen study revealed broiler body weight from 0 – 18 days of age was increased in birds fed

either the 600 or 900 µm corn PS, but from 18 – 42 days of age, broilers fed the 1200 or 1500 µm

treatment performed equally to those fed finer particles. Like the broiler digestibility study, birds

fed crumbled starter and pelleted grower and finisher in floor pens fared equally by the end of the

study, indicating larger corn PS may be beneficial when fed from 18 – 42 d of age, with a finer

corn PS being utilized at the beginning of life.

Pullet body weight was significantly influenced by corn PS treatments at 5, 10 and 16

weeks of age, with results trending at 17 weeks of age, where all pullets fed the 600 µm corn

treatment diets were the heaviest. Body weight gain was greatest for the 600 µm treatment birds

from week 0 – 5 and trended again at 16 – 17 weeks of age, indicating the 600 µm treatment had

the best feed to gain ratio in those weeks. Unlike the pullets, laying hens age 17 weeks and on

showed very few differences between the corn PS treatments. Layer body weight, percent

mortality, percent egg production, mean number of eggs per 28 d period, feed intake, feed

conversion (in kg feed/kg egg and kg feed/dozen eggs) and egg proportions were not significantly

different between treatments. Egg quality parameters (albumen height, Haugh units, meat spot

and blood spot enumeration) were not significantly different. Only yolk color was reduced in the

600 µm treatment yolks at 35 and 43 weeks of age and overall, possibly due to damaged

xanthophyll levels from the grinding or storage process of the 600 µm treatment corn.

Future work with broilers could focus on whether dietary corn particle size is affected by

the pelleting process and whether there is a post-pelleting effect on bird growth performance and

127

whether pellet durability index is affected by PS. Particle size of soybean meal could merit

similar research as that conducted herein, and a future digestibility study could help determine

whether there is an ideal PS where amino acids are best absorbed from soybean meal. Further

studies with pullets using greater numbers of replicates to hone in on the growing phase of

pullets, from hatch through 17 weeks of age could be beneficial. The layer study could be

replicated using different commercial strains of hens or in a different management style, such as

cage-free. All studies described previously indicate that while birds excel in growth and meet

current standards of production when full grown, there is further work to be done to hone in on an

optimum small corn particle size for young birds, especially in regard to growth, body weight

gain, and feed conversion for pullets.

128

APPENDIX A

Chapter 6 Summary Tables

Appendix A.1. Pullet starter diets

Ingredient % 600µm 900µm 1500µm

Corn1

61.17 61.17 61.17

Soybean meal (48%) 30.40 30.40 30.40

Limestone 0.90 0.90 0.90

Soybean oil 4.67 4.67 4.67

Mono-Dical Phos 1.86 1.86 1.86

Vit-TM premix2 0.40 0.40 0.40

Salt 0.41 0.41 0.41

DL-Methionine 0.19 0.19 0.19

L-Lysine 0.01 0.01 0.01

Calculated nutrients

ME(kcal/kg)3

3071.91 3071.91 3071.91

Crude protein 19.01 19.01 19.01

Lys 1.07 1.07 1.07

Met 0.49 0.49 0.49

Met + Cys 0.79 0.79 0.79

Trp 0.22 0.22 0.22

Ca 1.10 1.10 1.10

Available P 0.49 0.49 0.49

Analyzed Nutrients (%)4

Crude protein 18.71 19.11 18.86

Dry matter 92.27 88.53 89.71

Ether extract 6.36 7.15 6.92

Crude fiber 2.10 2.17 2.37

Ash 5.98 6.35 5.96 1 Corn was donated by cooperator Wenger Feeds, LLC (Rheems, PA).

2 Supplemented per kilogram of diet: vitamin A, 7,937 IU; vitamin D, 2,646 IU; vitamin E, 19.8 IU; riboflavin,

5.3 mg; pantothenic acid, 9.3 mg; niacin, 39.7 mg; choline, 401 mg; vitamin B12, 10.6 µm; biotin, 66.0 µg; Mn,

794 mg; Fe, 33.1 mg; I, 1.0 mg; Cu, 5.3 mg; Zn, 66.1 mg; and Se, 180 µg. 3 ME (kcal/kg) was calculated using the NRC (1994) equation 36.21 x CP + 85.44 x EE + 37.26 x NFE (for

corn grain). 4 All diets were analyzed in triplicate (N = 3) by Barrow-Agee Laboratories (Memphis, TN).

129

Appendix A.2. Pullet grower diets


Corn1

62.04 62.04 62.04

Soybean meal (48%) 26.00 26.00 26.00

Naked Oats 5.00 5.00 5.00

Limestone 0.96 0.96 0.96

Soybean oil 3.23 3.23 3.23


Vit-TM premix2 0.40 0.40 0.40

Salt 0.41 0.41 0.41



ME(kcal/kg)3

3039.04 3039.04 3039.04

Crude protein 17.63 17.63 17.63

Lys 4.84 4.84 4.84

Met 0.44 0.44 0.44

Met + Cys 0.74 0.74 0.74

Trp 0.19 0.19 0.19

Ca 1.10 1.10 1.10

Available P 0.47 0.47 0.47


Crude protein 18.71 18.08 17.54

Dry matter 89.16 88.01 89.54


Crude fiber 2.37 2.17 2.57






130

Appendix A.3. Pullet developer diets


Corn1

65.59 65.59 65.59

Soybean meal (48%) 23.00 23.00 23.00

Naked Oats 5.00 5.00 5.00

Limestone 0.96 0.96 0.96

Soybean oil 2.75 2.75 2.75


Vit-TM premix2 0.40 0.40 0.40

Salt 0.38 0.38 0.38



ME(kcal/kg)3

3038.99 3038.99 3038.99

Crude protein 16.50 16.50 16.50

Lys 0.89 0.89 0.89

Met 0.41 0.41 0.41

Met + Cys 0.69 0.69 0.69

Trp 0.18 0.18 0.18

Ca 1.09 1.09 1.09

Available P 0.46 0.46 0.46


Crude protein 16.39 17.06 16.64

Dry matter 88.66 87.94 89.32


Crude fiber 2.33 2.03 2.17






131

Appendix A.4. Pullet pre-lay diets


Corn1

54.57 54.57 54.57

Soybean meal (48%) 28.00 28.00 28.00

Naked Oats 5.00 5.00 5.00

Limestone 5.26 5.26 5.26

Soybean oil 4.19 4.19 4.19


Vit-TM premix2 0.40 0.40 0.40

Salt 0.40 0.40 0.40



ME(kcal/kg)3

2930.26 2930.26 2930.26

Crude protein 17.99 17.99 17.99

Lys 1.00 1.00 1.00

Met 0.47 0.47 0.47

Met + Cys 0.77 0.77 0.77

Trp 0.20 0.20 0.20

Ca 2.75 2.75 2.75

Available P 0.50 0.50 0.50


Crude protein 17.94 18.51 17.21

Dry matter 89.39 88.78 89.68


Crude fiber 2.17 2.07 2.40


2 Supplemented per kilogram of diet: vitamin A, 7,937 IU; vitamin D, 2,646 IU; vitamin E, 19.8 IU;

riboflavin, 5.3 mg; pantothenic acid, 9.3 mg; niacin, 39.7 mg; choline, 401 mg; vitamin B12, 10.6 µm; biotin,

66.0 µg; Mn, 794 mg; Fe, 33.1 mg; I, 1.0 mg; Cu, 5.3 mg; Zn, 66.1 mg; and Se, 180 µg. 3 ME (kcal/kg) was calculated using the NRC (1994) equation 36.21 x CP + 85.44 x EE + 37.26 x NFE (for


132

APPENDIX B

Chapter 7 Summary Tables

Appendix B.1. Hen diets phase 1, periods 1 & 2

Dietary treatments2

Ingredient % 600µm 900µm 1200µm 1500µm

Corn1

53.15 53.15 53.15 53.15

Soybean meal (48%) 28.30 28.30 28.30 28.30

Limestone 9.44 9.44 9.44 9.44

Soybean oil 6.27 6.27 6.27 6.27

Mono-Dical Phos 1.88 1.88 1.88 1.88

Vit-TM premix2 0.40 0.40 0.40 0.40

Salt 0.40 0.40 0.40 0.40

DL-Methionine 0.16 0.16 0.16 0.16


ME(kcal/kg)3

2900.01 2900.01 2900.01 2900.01

Crude protein 17.40 17.40 17.40 17.40

Lys 0.98 0.98 0.98 0.98

Met 0.43 0.43 0.43 0.43

Met + Cys 0.71 0.71 0.71 0.71

Trp 0.20 0.20 0.20 0.20

Ca 4.31 4.31 4.31 4.31

Available P 0.48 0.48 0.48 0.48


Crude protein 16.10 17.52 16.54 17.05

Dry matter 90.32 90.33 89.20 90.80

Ether extract 8.52 7.74 6.53 8.09

Crude fiber 2.30 2.37 4.60 2.30

Ash 13.10 12.45 11.25 12.76 1 Corn was donated by cooperator Wenger Feeds, LLC (Rheems, PA).


riboflavin, 5.3 mg; pantothenic acid, 9.3 mg; niacin, 39.7 mg; choline, 401 mg; vitamin B12, 10.6 µm;

biotin, 66.0 µg; Mn, 794 mg; Fe, 33.1 mg; I, 1.0 mg; Cu, 5.3 mg; Zn, 66.1 mg; and Se, 180 µg. 3 ME (kcal/kg) was calculated using the NRC (1994) equation 36.21 x CP + 85.44 x EE + 37.26 x NFE (for


133


Dietary treatments2


Corn1

54.38 54.38 54.38 54.38

Soybean meal (48%) 28.30 28.30 28.30 28.30

Calcium chips 4.72 4.72 4.72 4.72

Limestone 4.72 4.72 4.72 4.72

Soybean oil 5.06 5.06 5.06 5.06

Mono-Dical Phos 1.87 1.87 1.87 1.87

Vit-TM premix2 0.40 0.40 0.40 0.40

Salt 0.40 0.40 0.40 0.40

DL-Methionine 0.16 0.16 0.16 0.16


ME(kcal/kg)3

2900.06 2900.06 2900.06 2900.06

Crude protein 17.39 17.39 17.39 17.39

Lys 0.96 0.96 0.96 0.96

Met 0.43 0.43 0.43 0.43

Met + Cys 0.71 0.71 0.71 0.71

Trp 0.21 0.21 0.21 0.21

Ca 4.31 4.31 4.31 4.31

Available P 0.48 0.48 0.48 0.48


Crude protein 16.97 17.66 17.49 17.06

Dry matter 90.35 90.49 90.46 90.63

Ether extract 7.20 6.66 6.74 6.92

Crude fiber 2.30 2.33 2.23 2.20






134


Dietary treatments2


Corn1

61.76 61.76 61.76 61.76

Soybean meal (48%) 24.15 24.15 24.15 24.15

Calcium chips 4.28 4.28 4.28 4.28

Limestone 4.27 4.27 4.27 4.27

Soybean oil 3.06 3.06 3.06 3.06

Mono-Dical phos 1.67 1.67 1.67 1.67

Vit-TM premix2 0.40 0.40 0.40 0.40

Salt 0.37 0.37 0.37 0.37

DL-Methionine 0.04 0.04 0.04 0.04


ME(kcal/kg)3

2875.01 2875.01 2875.01 2875.01

Crude protein 16.00 16.00 16.00 16.00

Lys 0.86 0.86 0.86 0.86

Met 0.30 0.30 0.30 0.30

Met + Cys 0.56 0.56 0.56 0.56

Trp 0.18 0.18 0.18 0.18

Ca 3.95 3.95 3.95 3.95

Available P 0.44 0.44 0.44 0.44


Crude protein 15.51 15.31 16.54 15.69

Dry matter 90.28 90.45 90.19 90.73

Ether extract 4.95 5.09 5.18 5.10

Crude fiber 2.10 2.17 2.13 2.20






135

Appendix B.4. Egg proportions (g)

Hen age (wk) 23

Shell weight Yolk weight Albumen wt.

600µm 5.57 11.29 33.60

900µm 5.42 10.90 33.40

1200µm 5.64 11.58 34.22

1500µm 5.53 11.00 34.55

SEM 0.11 0.25 0.81

P-value 0.6147 0.2309 0.7222

Hen age (wk) 31

600µm 5.93 13.96 35.97

900µm 6.02 13.46 36.47

1200µm 6.03 14.05 36.33

1500µm 6.00 13.63 37.28

SEM 0.06 0.27 0.54

P-value 0.6556 0.3848 0.3555

Hen age (wk) 39

600µm 5.94 15.11 35.88

900µm 5.98 14.76 36.19

1200µm 5.94 14.84 35.09

1500µm 5.92 15.21 35.97

SEM 0.07 0.19 0.55

P-value 0.9607 0.2773 0.9787

Hen age (wk) Average

600µm 5.88 13.93 35.57

900µm 5.90 13.43 35.80

1200µm 5.93 13.86 35.86

1500µm 5.89 13.74 36.32

SEM 0.05 0.21 0.36

P-value 0.8835 0.3637 0.5187

136

Appendix B.5. Hen organ weights and lengths (43 weeks)1

Trt BW (kg) Mouth

Score

Tongue

score Gizzard (g)

Proventriculus

(g) Ceca (g)

Fat pad

(g)

# Preovulatory

follicles

Ovary +

preovulatory

follicles (g)

600 µm 1.57 0.33 0.00 22.97 7.27 7.80 44.80 5.33 39.07

900 µm 1.61 0.00 0.00 26.53 7.43 9.03 49.00 5.67 43.93

1200 µm 1.63 0.67 0.00 27.00 7.07 7.87 46.53 5.67 45.20

1500 µm 1.65 0.00 0.00 30.23 8.30 9.53 33.93 6.00 47.20

SEM 0.09 0.37 - 2.69 0.36 1.11 10.67 0.29 3.56

P-value 0.9419 0.5607 - 0.3632 0.1624 0.6295 0.7647 0.4872 0.4628

Trt

Pancreas,

duodenum

(g)

Jejunu

m (g)

Ileum

(g)

Small

intestine (g)

Duodenum

(cm)

Jejunum

(cm)

Ileum

(cm)

Small intestine

(cm)

600 µm 10.87 10.63 9.83 31.33 26.23 54.23 53.87 134.33

900 µm 11.07 10.43 10.03 31.53 28.97 52.03 53.87 134.87

1200 µm 11.90 12.93 12.27 37.10 29.83 57.77 55.17 142.77

1500 µm 12.07 13.07 13.77 38.90 28.10 54.17 53.87 136.27

SEM 0.59 0.97 1.27 2.32 1.36 2.54 1.71 4.51

P-value 0.4271 0.1677 0.1663 0.1113 0.3446 0.4944 0.9358 0.5547 1 N = 3 birds/treatment.

137

Appendix B.6. Hen organ weight as a percent of body weight (%) (43 weeks)1,2

Treatment Gizzard Proventriculus Pancreas,

duodenum Jejunum Ileum

Total small

intestine Ceca Fat pad

Ovary,

preovulatory

follicles

600µm 1.46 0.46 0.69 0.687 0.63 2.00 0.50 2.84 2.50

900µm 1.64 0.46 0.69 0.65 0.62 1.96 0.56 3.04 2.73

1200µm 1.65 0.44 0.73 0.80 0.76 2.29 0.48 2.81 2.75

1500µm 1.89 0.51 0.73 0.79 0.83 2.36 0.58 2.04 2.90

SEM 0.17 0.03 0.04 0.06 0.06 0.13 0.06 0.64 0.22

P-value 0.4583 0.5387 0.7245 0.3055 0.1146 0.1316 0.5514 0.7255 0.6348 1 Percentage data analyzed using an arcsine transformation.

2 N = 3 birds/treatment.

EFFECT OF CORN PARTICLE SIZE MILLING ON BROILER, PULLET ...

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