Nutritional factors influencing value of forages used as substrates for silage

Basim Refat

Nutritional factors influencing

value of forages used as

substrates for silage

Introduction

Russell et al 1992

Average distribution of protein and nitrogen

fractions in some feedstuffs

Soybean meal, 44% 49.9 11.0 9.0 75 3.0 2.0

Poor N utilization from silages is a product

of two consequences of ensilage

Solubilization of protein Protein solubilization reduces the proportion of undegraded

protein passing from the rumen to the small intestine.

Fermentation of soluble sugars to VFA

and lactic acid Energy yield and utilization from VFA and lactic acid is

considerably less than from non-fermented carbohydrate

(ARC1984)

Efficiency of utilization of fermented organic matter for microbial protein synthesis is only approximately

60 to 70% of that for energy from non-fermented feeds

Thomas and Thomas1985

Relationship between non-protein N intake, rumen

ammonia and voluntary intake of silage

Concentration of Ammonia :

threshold level for microbes requirements (50 mg/L; Satter and Slyter, 1974)

Forage type –Red clover and timothy seem to have lower NPN levels than

alfalfa

Select carbohydrate sources that break down rapidly in the rumen (Barley,

Molasses)

Processing: Increasing crop DM or by reducing crop pH / combination of both

Acid-type additives: formic acid

Polyphenolic compounds (Tannins) (tannins protein complex;= pH3.5- 8.0)

Inoculant(LAB)

Charmley et al. (1994)

Tabacco et al 2006

Inhibiting Proteolysis

Fate of dietary protein in dairy cows fed

combinations of alfalfa and corn silages

LAB

Increase the silage shelf-life by

inhibiting deleterious epiphytic microbial populations

Antibacterial activity

Produce ferulate esterase enzymes during fermentation

increase neutral detergent fiber degradation of the inoculated crop during ensiling.

Enhance animal performance when treated silage is fed to

ruminants

Lactobacillus plantarum

Positive effects on milk production : + 4.6% above untreated silage

(summarize of 9 published studies; Kung et al. 2003)

Improve protein preservation during ensiling

Soluble nonprotein N (NPN) fractions in silage

Produce greater microbial biomass

Contreras-Govea et al. (2011)

Silage fermentation characteristics (pH and g/kg DM) of

four combined experiments with no inoculant (Control), L.

plantarum (LP) or formic acid (FA).

Treatment P>F

Control LP FA

pH 4.38a 4.28b 4.25c <0.001

Lactic acid 61.0b 66.3a 12.1c <0.001

Acetic acid 20.5a 17.1b 5.7c <0.001

L:A ratio 3.1b 4.1a 1.8c <0.001

Ethanol 5.1a 4.5a 2.1b <0.001

Formic acid 0.0b

0.2b

19.5a

<0.001

Contreras-Govea et al. (2013)

Silage nutritive characteristics (g/kg DM) of four

combined experiments

Treatment P>F

Control LP FA

DM 339.1b 336.4b 350.0a 0.002

CP 189.7b 190.2b 193.7a 0.05

aNDF 327.7 317.0 323.2 0.127

ADF 227.7 218.5 222.4 0.090

WSC 11.1b 10.1b 63.0a <0.001

Contreras-Govea et al. (2013)

Silage soluble N fractions (g/kg total N) of four

combined experiments

Characteristic Treatment

Control LP FA P>F

NH3-N 34.0a 27.7b 12.4c <0.001

FAA-N 286.6a 262.1b 187.9c <0.001

Peptide-N 151.8b 162.6b 190.1a <0.001

NPN (total) 472.5a 440.7a 390.4b <0.001

Contreras-Govea et al. (2013)

LP vs. FA

Formic acid preserved the most protein and peptides during ensiling

Lactobacillus plantarum provided an intermediate level of

preservation relative to the untreated control.

Plant protease activity is highest on the first day of very high

after ensiling

FA treatment, which immediately drops pH, preserve more

protein than LAB.

lower pH and greater lactic acid concentration, lower acetic

acid and ethanol concentrations, homolactic fermentation in

LP than in the control

Contreras-Govea et al. (2013)

In vitro ruminal fermentation characteristics of

four combined experiments

Characteristic Treatment P>F

Control LP FA

Acetate (mM) 27.3 28.2 29.5 0.638

Propionate (mM) 10.6 10.7 10.0 0.687

Butyrate (mM) 4.7 4.7 4.4 0.659

A:P ratio 2.7b 2.7b 3.1a <0.001

Total VFA (mM) 42.6 43.5 43.9 0.936

Gas (mL/g DM) 155.5 152.3 155.2 0.402

Contreras-Govea et al. (2013)

In vitro ruminal fermentation characteristics of

four combined experiments

Characteristic Treatment P>F

Control LP FA

MNAN (mg/g DM) 10.3b 12.4ab 14.4a 0.002

MDM (mg/g DM) 343.5 356.4 361.1 0.376

MBY(mg MDM/100 mg TDM)

43.7b 47.3a 47.5a 0.012

MNAN = microbial non-ammonia N

MDM = microbial DM

MBY = microbial biomass yield

TDM = truly digested DM Contreras-Govea et al. (2013)

LP vs. FA

Ruminal microbial biomass production as measured by two methods

was highest on formic acid, intermediate on L. plantarum, and lowest

on untreated control.

Increased ruminal microbial biomass production on L. plantarum-

treated silage

related to its effects on protein preservation in the silo, which may

explain its positive effects on milk production in other studies.