Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: 7/24/2000
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Nineteen multiparous and 6 primiparous (ten ruminally fistulated) Holstein cows in early-mid lactation (82 ± 34 DIM) were assigned to a 5x5 Latin Square (21-d periods) and fed diets with different protein supplements to determine the effect of ruminal protein degradation on milk production and composition and on rumen variables. Total mixed diets were (DM basis) 43.5% corn silage, 22% alfalfa silage, 2% urea, and 31% concentrate (protein supplement plus rolled high moisture shelled corn, RHMSC). Diets were: Control, 31% RHMSC; SSBM, 22% RHMSC and 9% solvent soybean meal; ESBM, 21% RHMSC and 10% expeller soybean meal (Soy PlusÒ), BM, 25.5% RHMSC and 5.5% blood meal; and CGM, 24% RHMSC and 7% corn gluten meal. The crude protein content of the diets was 15.7, 19.1, 19.7, 20.3 and 19.3% respectively. Ruminal rates and extent of degradation of the protein supplements estimated by the inhibitor in vitro method (Broderick, 1987) were 0.17, 0.04, 0.01 and 0.009/h and 26, 58, 85 and 86% of total CP, for SSBM, ESBM, BM and CGM respectively. Rumen and omasal samples were also collected to determine the rates and extent of protein degradation in vivo. Control diet was lower in all milk yield parameters and in DMI, compared to the other diets. Milk yield was higher for cows fed ESBM and CGM, milk fat yield was higher for SSBM and CGM, but milk protein yield was not significantly different among cows fed SSBM, ESBM, BM and CGM.