Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: 7/26/2004
Publication Date: 7/26/2004
Citation: Brito, A.F., Broderick, G.A. 2004. Effects of different protein supplements on nitrogen utilization in dairy cows. ii. digesta flow and bacterial protein synthesis. [abstract]. Journal of Dairy Science. 87(1):161 Interpretive Summary:
Technical Abstract: Eight multiparous Holstein cows fitted with ruminal cannulae were randomly assigned to two 4 x 4 Latin squares to investigate the effects of RDP source on digesta flow and bacterial protein synthesis. All diets contained (% of DM): 20.7% alfalfa silage and 35.1% corn silage. The following protein supplements were added to the basal diet (% of DM): urea (1.9%; diet A), solvent soybean meal [(SSBM; 12.1%); diet B]; cottonseed meal [(CSM; 14.1%); diet C]; or canola meal [(CM; 16.1%); diet D]. Diets contained 16.6% CP. Digesta flow (Co-EDTA and YbCl2) and bacterial markers (15N) were continuously infused into the rumen. The omasal sampling technique was used to collect digesta from the omasal canal. Both DM and OM flows were lowest for cows fed diet A but similar among diets B, C, and D. Apparent ruminal dry matter digestibility (ARDMD) was highest on diet A, lowest on diet C, and intermediate on diets B and D. Organic matter apparently digested in the rumen (OMADR) and organic matter truly digested in the rumen (OMTDR) did not differ among diets. Fluid-associated bacteria (FAB), particleassociated bacteria (PAB), total bacterial flow, and bacterial efficiency were all higher in cows fed SSBM, CSM, or CM. Overall, bacterial nonammonia nitrogen (NAN) flow and efficiency were increased by feeding true protein supplements rather than a NPN source (urea).