ARS | Publication request: EFFECT OF LEVEL OF DIETARY CRUDE PROTEIN ON RUMINAL DIGESTION AND BACTERIAL NAN FLOW IN LACTATING DAIRY COWS

Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: July 26, 2004
Publication Date: July 26, 2004
Citation: Olmos Colmenero, J.J., Broderick, G.A. 2004. Effect of level of dietary crude protein on ruminal digestion and bacterial NAN flow in lactating dairy cows. [abstract]. Journal of Dairy Science. 87(1):223.

Technical Abstract: Ten ruminally fistulated Holstein cows were used in an incomplete 5 x 5 Latin square design with 4, 4-wk periods to assess the effects of different dietary CP levels on ruminal digestion and bacterial nonammonia nitrogen(NAN) flow. Diets contained (DM basis) 25% alfalfa silage, 25% corn silage, and 50% concentrate. High moisture corn was replaced with solvent soybean meal to increase CP from 13.7%, to 15.1%, 16.6%, 18.1%, and 19.6%. Samples of digesta were taken from the reticulo-omasal orifice and the true digesta flow was calculated using a triple marker approach (indigestible NDF, Co-EDTA and Yb-acetate). The marker used to quantify bacterial NAN was 15N. DM and OM intakes were not different among treatments. As expected, N intake increased linearly with CP content in the diet. DM and OM flow, apparent rumen OM digestibility (AROMD), OM truly digested in the rumen (OMTDR), and liquid associated bacteria (LAB) flow did not differ. The flows of particle associated bacteria (PAB) and total bacterial NAN, and bacterial efficiency were not different but significant linear effects of CP level were detected. Under the conditions of this study, total bacterial NAN was not increased by feeding more than 16.6 % CP.