Evaluation of urea and dried whey in diets of cows during early lactation.
Journal of Dairy Science
Thirty-three Holstein cows were fed one of three concentrate mixtures supplemented with all protein (soybean meal), 1% urea, or 1% urea and 30% dried whey from wk 3 through 16 postpartum. Total mixed rations contained 40% (dry matter basis) corn silage, 10% alfalfa hay, and 50% concentrate mixture. Diets were formulated to be isonitrogenous at 16% crude protein, but soluble nitrogen was formulated to be approximately 23, 30, and 42% of total nitrogen. Milk yield was similar (33.8, 33.4, and 33.2 kg/d) for cows fed the three diets, whereas production of 4% fat-corrected milk (29.9, 28.0, and 29.2 kg/d) and solids-corrected milk (30.3, 28.6, and 29.6 kg/d) was higher for cows fed soybean meal and urea-dried whey. Milk fat percentages (3.23, 2.94, and 3.23%) were lower when cows were fed urea, but milk protein (3.10, 3.04, and 3.04%) and solids-not-fat (8.74, 8.79, and 8.81%) were not affected by diet. Dry matter intakes (22.0, 20.2, and 23.1 kg/d) were highest for cows fed urea-dried whey and lowest for cows fed urea. Molar percentages of ruminal acetate (56.6, 50.3, and 50.2%) were highest for cows fed soybean meal, propionate (24.8, 28.6, and 25.0%) was highest for cows fed urea, and butyrate (13.6, 14.4, and 18.4%) was highest for cows fed urea-dried whey. Concentrations of ruminal ammonia (11.8, 20.3, and 13.5 mg/dl) and serum urea (19.5, 22.9, and 16.5 mg/dl) were highest for cows fed urea. Utilization of urea nitrogen for milk production was improved by adding dried whey to diets of early lactation cows.
Casper, D.P. and Schingoethe, D.J., "Evaluation of urea and dried whey in diets of cows during early lactation." (1986). Dairy Science Publication Database. 1549.