A Department of Cattle Physiology and Nutrition, Institute of Animal Science and b Department of Natural Resources, Institute of Field and Garden Crops,

aaDepartment of Cattle Physiology and Nutrition, Institute of Animal Science Department of Cattle Physiology and Nutrition, Institute of Animal Science

andand

bbDepartment of Natural Resources, Institute of Field and Garden Crops,Department of Natural Resources, Institute of Field and Garden Crops, Agricultural Research Organization, The Volcani Center, Agricultural Research Organization, The Volcani Center,

P.O. Box 6, Bet Dagan 50 250, Israel.P.O. Box 6, Bet Dagan 50 250, Israel.

ccRange Science Department, Utah State University, Logan 84322, USARange Science Department, Utah State University, Logan 84322, USA

Use of Tannin-Binding Chemicals to Assay Use of Tannin-Binding Chemicals to Assay for Tannins and their Negative Postingestive for Tannins and their Negative Postingestive

Effects in RuminantsEffects in RuminantsN. SilanikoveN. Silanikoveaa, A. Perevolotsky, A. Perevolotskybb and F. D. Provenza and F. D. Provenzacc

00 0-4990-499 500-1000500-100099

1010

1111

1212

1313

aa aa

bb

Effect of Q on Daily Feed Intake

Fee

d In

take

, K

g F

resh

Fee

d In

take

, K

g F

resh

Q Intake, g/dayQ Intake, g/day

00 1010 2020 3030 4040 5050 606055

66

77

88

99

1010

1111

1212

1313

00

200200

400400

600600

800800

10001000

12001200

Effect of Q on Daily Feed Intake

Fee

d In

take

, K

g F

resh

Fee

d In

take

, K

g F

resh

Q I

ntak

e, g

/day

Q I

ntak

e, g

/day

Days in ExperimentDays in Experiment

00-- 00 0-10000-1000 40-100040-1000 80-100080-100099

1010

1111

1212

1313

aa

bb

bbabab

Fee

d In

take

, K

g F

resh

Fee

d In

take

, K

g F

resh

Effects of PEG and Q on Feed Intake

PEG-Q Intake, g/dayPEG-Q Intake, g/day

00 55 1010 1515 2020 2525 3030 353500

55

1010

1515

2020Switching rationsSwitching rations CC

QQ

QQ -- PEGPEG

PEGPEG

Effect of Q on Daily Feed IntakeF

eed

Inta

ke,

Kg

Fre

shF

eed

Inta

ke,

Kg

Fre

sh

Days in ExperimentDays in ExperimentQ - 650 g/dayQ - 650 g/day

- -250250 g/day PEGg/day PEG

00 55 1010 1515 2020 2525 3030 353500

1010

2020

3030

4040

5050

6060

Switching rationsSwitching rationsCC

QQ

QQ -- PEGPEG

PEGPEG

Days in ExperimentDays in Experiment

Effects of Q and PEG on the Number of Eating Bouts

Num

ber

of E

atin

g B

outs

Num

ber

of E

atin

g B

outs

Q - 650 g/dayQ - 650 g/day - -250250 g/day PEGg/day PEG

00 55 1010 151500

1010

2020

3030

4040

5050

CC

QQ

QQ -- PEGPEG

PEGPEG

Effects of Q and PEG on the Duration of Eating Bouts

Dur

atio

n of

Eat

ing

Bou

ts,

min

Dur

atio

n of

Eat

ing

Bou

ts,

min

Sequential Number of Eating BoutSequential Number of Eating Bout

Q - 650 g/dayQ - 650 g/day - -250250 g/day PEGg/day PEG

00 55 1010 151500

5050

100100

150150

200200

250250CC

QQ

QQ -- PEGPEG

PEGPEG

Sequential Number of Eating BoutSequential Number of Eating Bout

Effects of Q and PEG on Eating Rate

Eat

ing

Rat

e, g

/min

Eat

ing

Rat

e, g

/min

Q - 650 g/dayQ - 650 g/day - -250250 g/day PEGg/day PEG

00 55 1010 151500

11

22

33

44

55

CC

QQ

QQ -- PEGPEG

PEGPEG

Sequential Number of Eating BoutSequential Number of Eating Bout

Effects of Q and PEG on Feed Intake per Eating Bout

Fee

d In

take

per

Eat

ing

Bou

t, K

gF

eed

Inta

ke p

er E

atin

g B

out,

Kg

Q - 650 g/dayQ - 650 g/day - -250250 g/day PEGg/day PEG

Tannins are plant secondary metabolites that have a Tannins are plant secondary metabolites that have a large number of free phenolic hydroxyl groups that form large number of free phenolic hydroxyl groups that form strong hydrogen bonds at multiple sites with proteins strong hydrogen bonds at multiple sites with proteins and carbohydrates. Tannins are found in the cell sap of and carbohydrates. Tannins are found in the cell sap of approximately 80% of woody and 15% of herbaceous approximately 80% of woody and 15% of herbaceous dicotyledenous species and occur at high levels in dicotyledenous species and occur at high levels in various forages. Tannins protect plants from herbivory various forages. Tannins protect plants from herbivory by inducing complex and multifactorial effects such as by inducing complex and multifactorial effects such as deterrence (i.e., rejection based on odour and taste), deterrence (i.e., rejection based on odour and taste), toxicity, and aversive postingestive feedback signals.toxicity, and aversive postingestive feedback signals.

Some artificial polymers such as water-soluble Some artificial polymers such as water-soluble polyvinyl pyrrolidone (PVP), water-insoluble polyvinyl pyrrolidone (PVP), water-insoluble polyvinyl polypyrrolidone (PVPP), and water-soluble polyvinyl polypyrrolidone (PVPP), and water-soluble polyethylene glycol (PEG) contains sufficient polyethylene glycol (PEG) contains sufficient oxygen molecules in their chain to form strong oxygen molecules in their chain to form strong hydrogen bonds with the phenol and hydroxyl hydrogen bonds with the phenol and hydroxyl groups in tannins.groups in tannins.

This review highlight the applied aspects of tannin-This review highlight the applied aspects of tannin-binding agents, particularly PEG, as an assay of tannins binding agents, particularly PEG, as an assay of tannins and their negative effects on feed intake and digestion in and their negative effects on feed intake and digestion in ruminants.ruminants.

NNOO

CHCH CHCH22

xx

(17)(17) ~~

++

++ (17)(17) ~~proanthocyanidinsproanthocyanidins

PolysaccharidePolysaccharidematrixmatrix

Effect of once-a-day supplementation of PEGEffect of once-a-day supplementation of PEG40004000on the activity of amylase and trypsin in faecal sampleson the activity of amylase and trypsin in faecal samples

from sheep fed carob leaves (n=4, mean ± SD).from sheep fed carob leaves (n=4, mean ± SD).

Trypsin ActivityTrypsin Activity unit/g DMunit/g DM

0.600.60aa ± 0.4 ± 0.40.980.98aa ± 0.3 ± 0.31.381.38bb ± 0.4 ± 0.41.891.89cc ± 0.4 ± 0.42.072.07cc ± 0.5 ± 0.5

Amylase ActivityAmylase Activityunit/g DMunit/g DM

0.50.5a a ± 0.3± 0.31.21.2b b ± 0.4± 0.43.73.7c c ± 0.5± 0.54.014.01cd cd ± 0.5± 0.54.304.30d d ± 0.5± 0.5

PEG IntakePEG Intakeg/dayg/day

00 12.5 12.5

252530305050

a,b,ca,b,c Values marked by different superscript letters are significantly Values marked by different superscript letters are significantly different (at least p<0.05). different (at least p<0.05).

Extractions of Tannins from Lyophilized Leaves Extractions of Tannins from Lyophilized Leaves with Various Solvents (After Hagerman, 1987)with Various Solvents (After Hagerman, 1987)

SolventSolvent

70% acetone70% acetone50% methanol50% methanol50% methanol, boiling50% methanol, boiling1% HCl in methanol1% HCl in methanol

OakOak

546546387387359359343343

MapleMaple

13831383111711179949949797

Extractions of Tannins from Lyophilized Maple Leaves Extractions of Tannins from Lyophilized Maple Leaves Collected on Various Dates in 1996 Collected on Various Dates in 1996

(After Hagerman, 1987)(After Hagerman, 1987)

SolventSolvent

70% 70% acetoneacetone

50% 50% methanolmethanol

MayMay2727

17941794

12281228

JulyJuly99

13811381

11171117

AugustAugust1313

692692

802802

Feed Intake and Growth in Lambs Fed Acacia cyanophylla Feed Intake and Growth in Lambs Fed Acacia cyanophylla Lindl. Foilage and Supplemented with Feed Block containing Lindl. Foilage and Supplemented with Feed Block containing Various Levels of PEG (After Ben Salem et al, Tunis, Lives. Various Levels of PEG (After Ben Salem et al, Tunis, Lives.

Prod. Sci., in press)Prod. Sci., in press)

PEG in Feed Blocks (%)PEG in Feed Blocks (%)

DM intake DM intake (g/d)(g/d)

AcaciaAcaciaFeed blockFeed blockDaily gain, g/dDaily gain, g/d

00DM intake DM intake

(g/d)(g/d)

3573571291291414

66DM intake DM intake

(g/d)(g/d)

4294291501503939

1212DM intake DM intake

(g/d)(g/d)

4614611451455050

1818DM intake DM intake

(g/d)(g/d)

5395391281286161

2424DM intake DM intake

(g/d)(g/d)

5165161451456363

Feed blocks were composed of: Olive cake (42%), wheat bran (27%), Feed blocks were composed of: Olive cake (42%), wheat bran (27%), wheat flour (11%), Quicklime (11%), urea (4.4%), salt (4.4%), mineral wheat flour (11%), Quicklime (11%), urea (4.4%), salt (4.4%), mineral and vitamin supplement (1%), and various level of PEGand vitamin supplement (1%), and various level of PEG

Digestibility (%) in sheep Fed Acacia Digestibility (%) in sheep Fed Acacia cyanophylla Lindl. Foilage and Supplemented cyanophylla Lindl. Foilage and Supplemented

with Feed Block containing Various Levels of PEG with Feed Block containing Various Levels of PEG (After Ben Salem et al, Tunis, Lives. Prod. Sci., in press)(After Ben Salem et al, Tunis, Lives. Prod. Sci., in press)

PEG in feed blocks (%)PEG in feed blocks (%)

OMOMCPCPNDFNDF

00

33.333.343.543.5

-8.4-8.4

66

39.539.550.950.9 5.85.8

1212

40.340.354.954.914.814.8

1818

43.243.255.155.117.517.5

2424

51.251.257.257.226.326.3

Feed blocks were composed of: Olive cake (42%), wheat bran (27%),Feed blocks were composed of: Olive cake (42%), wheat bran (27%),wheat flour (11%), Quicklime (11%), urea (4.4%), salt (4.4%), mineral wheat flour (11%), Quicklime (11%), urea (4.4%), salt (4.4%), mineral and vitamin supplement (1%), and various level of PEGand vitamin supplement (1%), and various level of PEG

PEG-b = (Cst - Cbl) - (Csm - Cbl) x APEG / (Cst - Cbl) x SwPEG-b = (Cst - Cbl) - (Csm - Cbl) x APEG / (Cst - Cbl) x Sw

Where: Cst, Cbl, and Csm are the 14C counts of the Where: Cst, Cbl, and Csm are the 14C counts of the standard, blank and sample, receptively, APEG is the standard, blank and sample, receptively, APEG is the amount of PEG in the test tube and Sw is the dry weight of amount of PEG in the test tube and Sw is the dry weight of the plant tissue. PEG-b was expressed as g / 100 g Sw.the plant tissue. PEG-b was expressed as g / 100 g Sw.

Food intake, g DM/dFood intake, g DM/d

Digestibility, g/kgDigestibility, g/kg

OMOM

ProteinProtein

Cell wall (NDF)Cell wall (NDF)

805805aa

451 451 aa

102 102 aa

351 351 aa

12021202bb

605605bb

405 405 bb

557 557 bb

3030

1010

88

77

a,ba,b Within rows, values marked by different superscript letters Within rows, values marked by different superscript letters are significant at P < 0.001.are significant at P < 0.001.

Dry matter intake, and digestibility of organic matter, Dry matter intake, and digestibility of organic matter, protein, and cell wall of goats fed carob leaves with protein, and cell wall of goats fed carob leaves with

or without PEG supplementation.or without PEG supplementation.

No PEGNo PEG With PEGWith PEG SESE

Rumen volumeRumen volumeAbsolute, littersAbsolute, littersFraction of BW, g/kgFraction of BW, g/kgFraction of Intake, g/KgFraction of Intake, g/KgRumen DM contentRumen DM contentAbsolute, kgAbsolute, kgFraction of BW, g/kgFraction of BW, g/kgFraction of Intake, g/KgFraction of Intake, g/Kg

3.853.85aa

110.1 110.1 aa

4.784.78

1.16 1.16 aa

33.0 33.0 aa

1.441.44

5.115.11bb

145.1 145.1 bb

4.254.25

1.52 1.52 bb

43.5 43.5 bb

1.261.26

0.10.144

0.30.3

0.080.0811

0.20.2 a,ba,b Within rows, values marked by different superscript letters Within rows, values marked by different superscript letters are significant at P < 0.01.are significant at P < 0.01.

No PEGNo PEG With PEGWith PEG SESE

Rumen volume and dry matter content* in goats fed carob Rumen volume and dry matter content* in goats fed carob leaves with, or without PEG supplementationleaves with, or without PEG supplementation

MRT, hoursMRT, hours

RumenRumenOmasum + abomasumOmasum + abomasumForegutForegutIntestineIntestineTotal GITTotal GIT

No PEGNo PEG With PEG With PEG

24.924.9 21.7 21.7 2.72.7aa 9.2 9.2bb 27.6 27.6 aa 30.9 30.9 bb 19.4 19.4 aa 6.1 6.1 bb 47.2 47.2 aa 35.1 35.1 bb

No PEGNo PEG With PEG With PEG

33.2 31.0 33.2 31.0 11.5 11.7 11.5 11.7 44.7 42.7 44.7 42.7 16.9 16.9 aa 10.4 10.4 bb 61.7 61.7 aa 53.7 53.7 bb

a,ba,b Within rows, values marked by different superscript letters are significant at P < 0.01, Within rows, values marked by different superscript letters are significant at P < 0.01, except for the passage rate of the liquid phase in the foregut, for which P < 0.05.except for the passage rate of the liquid phase in the foregut, for which P < 0.05.

Liquid phaseLiquid phase Particulate phaseParticulate phase

Passage rate of the digesta liquid and particulate phases in Passage rate of the digesta liquid and particulate phases in goats fed carob leaves with, or without PEG supplementation goats fed carob leaves with, or without PEG supplementation

Tannin + Protein = Tannin-Protein complexesTannin + Protein = Tannin-Protein complexes

Tannin + PVP/PEG = Tannin-PVP/PEG ComplexesTannin + PVP/PEG = Tannin-PVP/PEG Complexes

PEG, polyethylene glycolPEG, polyethylene glycol

PVP, polyvinyl pyrrolidonePVP, polyvinyl pyrrolidone

Tannin-Protein complexes + PEG = Tannin-Protein complexes + PEG = Tannin-PEG complexes + ProteinTannin-PEG complexes + Protein

Tannin + Protein + PVP/PEG = Tannin + Protein + PVP/PEG = Tannin-PVP/PEG complexes + ProteinTannin-PVP/PEG complexes + Protein

Gas (ml)Gas (ml)

25.325.335.335.335.335.336.036.035.235.233.833.828.428.426.226.226.026.025.625.6

ControlControl

PEG 2000PEG 2000PEG 4000 PEG 4000 PEG 6000PEG 6000PEG 10000PEG 10000PEG 20000PEG 20000PEG 35000PEG 35000PVP 10000PVP 10000PVP 40000PVP 40000PVP 360000PVP 360000PVPPPVPP

Effect of addition of polyethylene glycol (PEG), Effect of addition of polyethylene glycol (PEG), and polyvinyl pyrrolidone (PVP)and polyvinyl pyrrolidone (PVP)

Dichostachys cinereaDichostachys cinerea

Increase(%)Increase(%)

39.539.539.539.542.142.141.441.439.139.133.633.612.212.2 3.33.3 2.72.7 0.90.9

Tannic acidTannic acid

0.5200.5200.6100.6100.6050.6050.5920.5920.6130.6130.6000.6000.2260.2260.2020.2020.2140.214

Quebracho tanninsQuebracho tannins

0.2930.2930.3140.3140.2930.2930.2900.2900.3030.3030.2870.2870.2660.2660.2800.2800.2730.273

PEG 2000PEG 2000PEG 4000PEG 4000PEG 6000PEG 6000PEG 10000PEG 10000PEG 20000PEG 20000PEG 35000PEG 35000PVP 10000PVP 10000PVP 40000PVP 40000PVP 360000PVP 360000

Binding (turbidity at 500nm) of polyethylene glycol (PEG), Binding (turbidity at 500nm) of polyethylene glycol (PEG), and polyvinyl pyrrolidone (PVP) with tannins at pH 6.6and polyvinyl pyrrolidone (PVP) with tannins at pH 6.6

Quantification of cell wall constituentsQuantification of cell wall constituents......

Standard procedure (Direct)Standard procedure (Direct)

Leaves/faecesLeaves/faeces NDF, ADF or ADLNDF, ADF or ADL

Sequential procedureSequential procedure

Leaves/faecesLeaves/faeces NDFNDF ADFADF ADLADL

Fiber levels in Fiber levels in Acacia salignaAcacia saligna leaves leaves & faeces of sheep & goats& faeces of sheep & goats

ADFADF ADLADL

ADF/ADLADF/ADLContentsContents

LeavesLeaves

Sheep feacesSheep feaces

Goat feacesGoat feaces

Direct Direct (mg/g)(mg/g)

298298

618618

625625

Sequential Sequential (mg/g)(mg/g)

431431

581581

586586

Direct Direct (mg/g)(mg/g)

155155

469469

472472

Sequential Sequential (mg/g)(mg/g)

237237

440440

445445

Protein in ADF & ADL in Protein in ADF & ADL in Acacia salignaAcacia saligna leaves leaves & faeces of sheep & goats & faeces of sheep & goats

ADFADF ADLADL

ADF/ADLADF/ADLContentsContents

LeavesLeaves

Sheep feacesSheep feaces

Goat feacesGoat feaces

Direct Direct (mg/g)(mg/g)

1515

107107

101101

Sequential Sequential (mg/g)(mg/g)

46.246.2

104104

101101

Direct Direct (mg)(mg)

11.911.9

102102

9797

Sequential Sequential (mg)(mg)

34.234.2

93.593.5

88.788.7

Condensed tannins (CT) in ADF & ADL in Condensed tannins (CT) in ADF & ADL in Acacia salignaAcacia saligna leaves & faeces of sheep & goats leaves & faeces of sheep & goats

ADFADF ADLADL

CTCT(A550nm)(A550nm)

Leaves..Leaves..

Sheep feacesSheep feaces

Goat feacesGoat feaces

Direct Direct (mg)(mg)

7.37.3

23.423.4

21.621.6

Sequential Sequential (mg)(mg)

46.246.2

17.417.4

18.318.3

Direct Direct (mg)(mg)

4.44.4

12.512.5

12.712.7

Sequential Sequential (mg)(mg)

2020

10.510.5

13.213.2

0010102020303040405050606070708080

33 44 44 .. 77 55 .. 55 66 66 .. 66 77

Tannic acidTannic acid QuebrachoQuebracho Acioa barteriAcioa barteri Piliostigma reticulatumPiliostigma reticulatum

Binding of PVPP with tannins at different pHBinding of PVPP with tannins at different pH

pHpH

Bin

din

g (

%)

Bin

din

g (

%)

Correlations between tannin levels & Correlations between tannin levels & increase in gasincrease in gas

* * PP < 0.05, ** < 0.05, ** PP < 0.01, *** < 0.01, *** PP < 0.001, n = 15 < 0.001, n = 15

% Increase in:% Increase in:

Gas at 24 hGas at 24 hRateRateExtentExtentArea up to 24 hArea up to 24 hArea up to 96 hArea up to 96 h

TanninsTannins

0.64*0.64*0.490.49

0.75**0.75** 0.64*0.64*

0.78**0.78**

Condense Condense d taninsd tanins

0.75**0.75** 0.78**0.78**

0.320.32 0.77**0.77** 0.64*0.64*

PPC-BSA PPC-BSA dyedye

0.84***0.84***0.69**0.69**

0.85***0.85*** 0.84***0.84*** 0.94***0.94***

PPC-BSA PPC-BSA pptionpption

0.98***0.98*** 0.90***0.90***0.71**0.71**

0.97***0.97*** 0.96***0.96***

Binding of tannins with PVPP was highest at pH 3 Binding of tannins with PVPP was highest at pH 3 to 4 and lowest at pH 7.to 4 and lowest at pH 7.

In the pH range 3 to 7, binding of PEGs was In the pH range 3 to 7, binding of PEGs was higher than that of PVPs. higher than that of PVPs.

For all the tannins studied except tannic acid, For all the tannins studied except tannic acid, binding to PVPs was the same from pH 4.7 to 7. binding to PVPs was the same from pH 4.7 to 7. Similar results were obtained for PEGs of 6000 or Similar results were obtained for PEGs of 6000 or higher mol. wt. except quebracho tannins for higher mol. wt. except quebracho tannins for which binding increased as the pH was increased which binding increased as the pH was increased from pH 3 to 7.from pH 3 to 7.

Per cent increase in gas was highest with PEGsPer cent increase in gas was highest with PEGsfollowed by PVPs & PVPPs. followed by PVPs & PVPPs.

Among PEGs, PEG 35000 was least effective. Among PEGs, PEG 35000 was least effective. Efficiency of other PEGs was almost similar.Efficiency of other PEGs was almost similar.

PEG 6000 was preferred as binding was highest PEG 6000 was preferred as binding was highest at near neutral pH.at near neutral pH.

The information obtained from PEG-b to plants seemsThe information obtained from PEG-b to plants seems to be equivalent to that obtained from PPC. to be equivalent to that obtained from PPC.

However, PEG-b has advantage over PPC in cases where However, PEG-b has advantage over PPC in cases where there is no alternative for preservation of the samples there is no alternative for preservation of the samples except by air-drying, and in cases where the tannins except by air-drying, and in cases where the tannins extractability is low. extractability is low.

Lignin - another major component of plant cell walls - and Lignin - another major component of plant cell walls - and tannins have similar effects on forage use by herbivores. tannins have similar effects on forage use by herbivores.

The separation between the effects of lignin and tannin is The separation between the effects of lignin and tannin is also difficult because tannins and tannin-protein complexes also difficult because tannins and tannin-protein complexes may be analyzed as lignin, neutral detergent insoluble may be analyzed as lignin, neutral detergent insoluble nitrogen, and therefore will increase artificially the content nitrogen, and therefore will increase artificially the content of neutral detergent fiber and acid detergent fiber in plant of neutral detergent fiber and acid detergent fiber in plant and fecal samples.and fecal samples.

The tannin effects showed a non-linear dependence on the The tannin effects showed a non-linear dependence on the tannin content of the tested material. tannin content of the tested material.

This effect could be explained in terms of combination of a This effect could be explained in terms of combination of a reduction in the rate of degradation of potentially reduction in the rate of degradation of potentially degraded material, and of a capacity to bind and hold free degraded material, and of a capacity to bind and hold free material. material.

The tannin effect was not related to the content of non-The tannin effect was not related to the content of non-degradable material. degradable material.

Different tannins in different plant samples may different Different tannins in different plant samples may different not on basis of content, but also on the basis of ability to not on basis of content, but also on the basis of ability to affect degradation, and to bind free materials. affect degradation, and to bind free materials.

According to Provenza (1995), there is a fine line between According to Provenza (1995), there is a fine line between satiety (positive postingestive feedback) and surfeit satiety (positive postingestive feedback) and surfeit (negative postingestive feedback), hence, preferences (negative postingestive feedback), hence, preferences and aversions to energy sources or specific nutrients are and aversions to energy sources or specific nutrients are a compromise response.a compromise response.

Consequently, neutralization of the negative effects of a Consequently, neutralization of the negative effects of a fodder will accentuate its positive effects.fodder will accentuate its positive effects.

However, supplemental PEG will not lead inevitably to However, supplemental PEG will not lead inevitably to greater use of high-tannin plants, or better animal greater use of high-tannin plants, or better animal performance. Unless the alternative forages are equal to or performance. Unless the alternative forages are equal to or lower in quality - nutritionally (e.g., macronutrients) and lower in quality - nutritionally (e.g., macronutrients) and toxicologically (e.g., tannins, alkaloids, terpens) - than the toxicologically (e.g., tannins, alkaloids, terpens) - than the high-tannin plants, animals may eat low-tannin plants of high-tannin plants, animals may eat low-tannin plants of higher nutritional quality, regardless of supplemental PEG.higher nutritional quality, regardless of supplemental PEG.

Overall, feeding Q was associated with lowered FI and Overall, feeding Q was associated with lowered FI and shorter duration of eating bouts, mainly of the first eating shorter duration of eating bouts, mainly of the first eating bout, immediately after distribution of the diet. bout, immediately after distribution of the diet.

Larger portion of the diet was consumed posterior to 180 Larger portion of the diet was consumed posterior to 180 min after distribution in Q-fed heifers. Eating rate and the min after distribution in Q-fed heifers. Eating rate and the water to food ratio were not affected by Q.water to food ratio were not affected by Q.

The effects of Q on FI were attenuated by feeding PEG. The effects of Q on FI were attenuated by feeding PEG.

Heifers adapted effectively to the CT-rich CMD by Heifers adapted effectively to the CT-rich CMD by increasing the number eating bouts and the portion of diet increasing the number eating bouts and the portion of diet consumed posterior to 180 min after distribution, so that consumed posterior to 180 min after distribution, so that no differences in FI were noted on the last day of each no differences in FI were noted on the last day of each feeding cycle. feeding cycle.

Data are interpreted to show that: Data are interpreted to show that:

Negative effects of Q on FI derive from astringency of Negative effects of Q on FI derive from astringency of CT and\ short-term post-ingestive malaise; CT and\ short-term post-ingestive malaise;

The increased number of eating bouts and their wider The increased number of eating bouts and their wider partition throughout the day are means to preserve the partition throughout the day are means to preserve the ruminal environment in Q-fed heifers; ruminal environment in Q-fed heifers;

PEG has the potential to neutralize negative effects of PEG has the potential to neutralize negative effects of CT in cattle.CT in cattle.