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 Objective The 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. Effect or ammoniation and fibrolytic enzyme on total-tract NDF digestibility Ammoniation effect; P = 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 Home of “Idaho Gem” * * † † † † = Straw main effect (P < 0.10) * = Straw main effect (P < 0. 05) Pooled SE = 3.4 No enzyme main effect was noted (P > 0.10) 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. 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: (fibrolytic enzyme main effects were not observed)