Effects of maturity at ensiling of bermudagrass and fibrolytic enzyme application on the performance of early-lactation dairy cows

Abstract

The objective of this study was to examine effects of adding fibrolytic enzymes to diets containing bermudagrass ensiled after 4 or 7 wk of regrowth on the diet digestibility, ruminal fermentation and performance of lactating cows, and the interaction of the treatments. In experiment 1, 64 Holstein cows (22 ± 4 d in milk) were assigned to an experiment with a 2 × 2 factorial treatment arrangement and a 56-d duration. Treatments were diets containing 4 or 7 wk regrowth bermudagrass silage without or with an exogenous fibrolytic enzyme cocktail. The cellulase-xylanase enzyme was applied at 2.33 g/kg of total mixed ration dry matter (DM) during mixing immediately before feeding. Experiment 2 was aimed at examining treatment effects on the ruminal fermentation profile. Four ruminally cannulated cows were assigned to the 4 treatments using a 4 × 4 Latin square design with 14-d periods. No enzyme by maturity interaction was detected for any measurement. Regardless of forage maturity, applying the fibrolytic enzyme did not affect DM intake, milk yield, apparent digestibility, feed efficiency, energy balance, and ruminal fermentation though it tended to increase milk lactose concentration (4.88 vs. 4.81%). Feeding the 4-wk diet instead of the 7-wk diet increased DM intake (22.4 vs. 21.3 kg/d), digestibility of DM, neutral detergent fiber, and acid detergent fiber, and tended to increase 3.5%-fat corrected milk yield (47.2 vs. 44.3 kg/d) and milk fat yield (1.88 vs. 1.73 kg/d). Therefore, daily intake of net energy and secretion of milk energy were greater for the 4-wk diet. In addition, the 4-wk diet increased the ruminal concentrations of acetate, propionate, valerate, lactate, and total volatile fatty acids, and decreased ruminal pH, without affecting the acetate:propionate ratio. Feeding fibrolytic enzymes did not improve the performance of early-lactation dairy cows, but harvesting the forage earlier tended to improve milk production.