Effect of an exogenous fibrolytic enzyme on the performance of dairy cows consuming a diet with a high proportion of bermudagrass silage

We previously reported that milk production by dairy cows was increased by adding specific xylanase-rich (XYL) and xylanase-cellulase enzymes to corn silage-based diets containing 0 or 10% bermudagrass silage. This study examined effects of adding XYL on the intake and performance of lactating dairy cows consuming a totally mixed ration (TMR) formulated with a greater proportion of bermudagrass silage. Endoglucanase and xylanase activities of XYL were 3,283 and 46,281 μmol/min/mL, respectively. Forty lactating Holstein cows (16 multiparous and 24 primiparous; 21 ± 3 days in milk; body weight 589 ± 73 kg) were stratified by milk production and parity and assigned randomly to Control and XYL diets. The TMR (crude protein of 16.2% of dry matter [DM], neutral detergent fiber of 36.4% of DM, and net energy for lactation of 1.65 Mcal/kg of DM) contained 20% bermudagrass silage, 25% corn silage, and 55% concentrate (DM basis). Immediately before the a.m. (0700 h) and p.m. (1300 h) feedings, the enzyme was sprayed on the XYL diet at the rate of 1 mL/kg of TMR DM in a Calan data ranger and mixed. A second data ranger was used to feed control cows. Cows were fed experimental diets for 70 d after they were fed a common diet for a 9-d covariate period. The experiment had a randomized complete block design. The statistical model included effects of enzyme, parity, week, and their interactions as well as covariate milk production or DM intake. The random effect was cow nested within treatment. Application of XYL did not (P > 0.10) affect milk yield (35.1 vs. 36.2 kg/d), DM intake (24.0 vs 23.7 kg/d for XYL and Control), 3.5% fat-corrected milk (FCM) (36.1 vs. 36.9 kg/d), yields of milk fat (1.29 vs. 1.31 kg/d) and protein (1.07 vs. 1.08 kg/d), milk fat concentration (3.65 vs. 3.61%), and body weight change (0.26 vs. 0.33 kg/d) compared with control cows. However, cows fed the diet treated with XYL had greater milk protein concentration (P = 0.01; 3.02 vs. 2.95%) and tended to have less feed efficiency (P = 0.06; 1.52 vs. 1.57 kg of FCM/kg of DMI) compared with cows fed the control diet. Adding XYL to a diet containing 20% bermudagrass silage and 25% corn silage did not improve DM intake or milk production.