Forty-four lactating Holstein cows (173±30 DIM, 42.5±6.8 kg of milk, 4.03±0.69% fat, 674±78 kg of
body weight) were used in an 8-wk, completely randomized trial with a 2 × 2 factorial arrangement of treatments to determine the effect of forage source and supplemental
cellulase enzyme on performance. Treatments included 2 forage combinations (corn silage plus 12.2% dry matter, DM, from either alfalfa hay or Tifton 85 bermudagrass haylage) with or without a commercial
cellulase enzyme applied to the total mixed ration at the rate of 4 g/head per day (Promote N.E.T.-L, Cargill Animal Nutrition, Minneapolis, MN). Experimental diets were formulated to provide similar concentrations of
protein (16.5% of DM), energy (1.63 Mcal of net energy for lactation/kg of DM), and neutral
detergent fiber (41.7% of DM) and were fed once daily as a total mixed ration behind
Calan doors for ad libitum intake. The
cellulase enzyme provided 1,200
cellulase units of activity/g of product and was applied to the total mixed ration and allowed to mix for 5min before feeding. Before beginning the trial, all cows were trained to use
Calan (American
Calan, Northwood, NH) doors and then fed the alfalfa hay-based diet for 2 wk. Data collected during wk 2 were used as a covariate in the statistical analysis. At the beginning of the 6-wk experimental period, cows were assigned randomly to 1 of the 4 experimental diets. No interactions were observed between forage and
enzyme for any measures. Daily DM intake; milk yield; concentrations of milk fat, true
protein,
lactose, and solids not fat; energy-corrected milk yield; and dairy efficiency were not different among alfalfa or Tifton 85 bermudagrass rations with or without
cellulase enzyme supplementation. The results of this trial indicate that Tifton 85 bermudagrass haylage can replace alfalfa hay in diets fed to high-producing, lactating dairy cows without depressing DM intake or milk yield when rations are balanced for NDF. Although supplemental
cellulase enzymes have been shown to improve ration digestibility and animal performance in previous trials, no advantages were observed in the current trial.