Effects of forage type on production of dairy cows supplemented with whole cottonseed, tallow, and yeast

Effects of increasing concentrations of alfalfa hay fed in diets containing com silage, whole cottonseed, tallow, and yeast were studied using 36 midlactation Holstein cows in a 3 X 4 factorial arrangement of treatments with three forage and four fat treatments fed as TMR in three 28-d periods. Forages were 1) 50% corn silage, 2) 37.5% corn silage and 12.5% alfalfa hay, and 3) 25% corn silage and 25% alfalfa hay. Fat treatments were 1) control (O% added fat), 2) 2.5% tallow, 3) 2.5% tallow and 12% whole cottonseed, and 4) 12% whole cottonseed. Yeast was imposed across all treatments and fed to half of the cows continuously throughout the experiment. Statistical models including effect of treatment imposed in the previous period indicated no carry-over effects. Production of milk (21.0 vs. 22.8 kg/d), fat (666 vs. 809 g/d), FCM (19.9 vs. 22.9 kg/d), and SCM (19.9 vs. 22.7 kg/d) were lower for cows fed whole cottonseed-corn silage diets than for those fed whole cottonseed-alfalfa hay diets. Added tallow increased milk production with all forage treatments but tended to decrease milk fat percentage with corn silage versus alfalfa hay diets. Tendency toward lower DM, OM, NDF, and ADF digestibilities suggested that fats probably had more negative effects on ruminal fermentation when diets were based on corn silage as the only forage. The depression in milk production and fat percentage that was due to cottonseed or tallow inclusion in corn silage diets was overcome by replacing 25 to 50% of the corn silage DM with alfalfa hay. Yeast treatment had no effect on measured parameters