Effect of Exogenous Fibrolytic Enzyme on Digestibility of Ammoniated or Non-ammoniated Bluegrass Seed Straw Fed to Beef Cattle

 J.I. Szasz†, C.W. Hunt†, L.R. Kennington†, and K.A. Johnson‡

†University of Idaho and ‡Washington State University

Research ObjectiveThe objective of this research was to determine the effect of

exogenous fibrolytic enzyme on the digestibility of ammoniated or non-ammoniated bluegrass seed straw

Introduction

Open-field burning of crop aftermath has been a critically important management practice for grass seed production. This practice serves numerous agronomic benefits and provides for sustained (>10 yr) seed production from perennial grass fields. Environmental and health concerns have resulted in legislation that restrict the burning of crop residues in many portions of the NW.

As a result, bluegrass straw has become a readily available forage source for livestock producers. However, high fiber content characteristic of straws requires that methods be implemented that improve its feeding value. Research has indicated that exogenous fibrolytic enzymes may increase fiber digestibility (Beauchemin et al., 1995 and Feng et al., 1996). By improving fiber digestibility, fibrolytic enzymes may have a practical application in feeding systems that utilize bluegrass straw.

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Enzyme Ammoniation

%

Effect or ammoniation and fibrolytic enzyme on total-tract NDF digestibility

Ammoniation effect; P = 0.002

SE = 0.8

Implications Few ammoniation by fibrolytic enzyme interactions

were observed for variables measured, suggesting lack of potential for an additive benefit.

Consistent with literature on other low quality roughages, ammoniation enhanced ruminal and total tract digestion. Addition of fibrolytic enzymes did not enhance digestion of bluegrass straw, perhaps indicating that optimal fiber digestion was achieved by ruminal microorganisms without the complement of exogenous enzymes

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Non-ammoniatedAmmoniated

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*†

††

† = Straw main effect (P < 0.10)* = Straw main effect (P < 0. 05)

Pooled SE = 3.4

0102030405060708090

%

No enzymeEnzyme

No enzyme main effect was noted (P > 0.10)

8 16 24 36 48 96

Hour of ruminal incubation

Effect of ammoniation and exogenous fibrolytic enzyme on in situ NDF disappearance of bluegrass straw

Materials and Methods

4 x 4 Latin square design metabolism study 4 yearling Angus crossbred heifers (mean BW 406 kg) 14 d of diet adaptation followed by 7 d of sampling 2 x 2 factorial arrangement of treatments testing the main effects and interactions of ammoniation (5 percent) and exogenous fibrolytic enzyme supplementation Chemical composition of straws:

Exogenous fibrolytic enzyme:

Enzyme application method:

Ammoniated – 93% DM, 94% OM, 70.4% NDF, 15.2% CP Non-ammoniated – 93% DM, 94% OM, 84% NDF, 4.3% CP

Contained xylanase and cellulase activity 676 mol reducing sugars/g CP/min (20.9% CP)

Freshly prepared enzyme solution was mixed with straw at a rate of 0.22 g enzyme (4.4 IU xylanase)/kg.

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DM fill IADF turnover pH Ace:prop

kg or %

/h

Control

Ammoniation

No Enzyme Enzyme

Ammoniated

Non- ammoniated

Effect of ammoniation of bluegrass straw on ruminal kinetics and ruminal fluid characteristics

Ammoniation effect; P < 0.05

SE: 0.37 0.001 0.07 0.10

(fibrolytic enzyme main effects were not observed)