|Olmos Colmenero, J - UW-MADSISON|
|Brito, A - UW-MADISON|
|Reynal, S - UW-MADISON|
Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: July 25, 2002
Publication Date: N/A
Technical Abstract: Sixteen multiparous and 8 primiparous Holstein cows (8 ruminally fistulated) were randomly assigned to six 4 x 4 Latin squares to assess the effect of NPN level in alfalfa and red clover silages on milk production, ruminal metabolites, microbial protein synthesis, and ruminal escape of amino acids and peptides. The experimental diets contained (DM basis): 50% control alfalfa silage (AS), 50% formic acid-treated alfalfa silage (AAS), 50% red clover silage (RCS1, lower NDF and CP than AS), or 50% red clover silage (RCS2, similar to AS in NDF and CP). Diets were formulated to contain about 17% CP and NDF content was 28.0, 29.0, 27.0 and 29%, respectively, for diets AS, AAS, RCS1 and RCS2. DMI and milk yield were higher for AS and AAS compared to RCS2, whereas RCS1 was intermediate. Fat and protein yield, MUN and rumen NH3 were higher for the alfalfa silages relative to both red clover silages. Apparent digestibilities of DM and NDF were highest on RCS2, intermediate on RCS1 and lowest on the alfalfa silages. Rumen pH, acetate, propionate and acetate:propionate ratio did not differ. RCS1 had higher N efficiency than the alfalfa silages while RCS2 was intermediate. Overall, feeding alfalfa silages resulted in greater DMI and milk yield than feeding red clover silages; however, N utilization, BW gain, and nutrient digestibilities were greater in cows fed red clover silages.