Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: 7/23/2003
Publication Date: 7/23/2003
Citation: BRITO, A.F., BRODERICK, G.A. EFFECTS OF DIFFERENT DIETARY RATIOS OF ALFALFA AND CORN SILAGE ON MILK PRODUCTION AND RUMEN METABOLISM IN LACTATING DAIRY COWS. JOURNAL OF DAIRY SCIENCE. 2003. v. 86 (Suppl. 1). Abstract 62. Interpretive Summary:
Technical Abstract: Diluting alfalfa silage with corn silage may be useful for improving N efficiency in dairy cattle. Twenty-eight lactating Holstein cows (8 ruminally fistulated) were randomly assigned to 7, 4 x 4 replicated Latin squares with 28-d periods to assess the effects of different ratios of alfalfa to corn silage on milk production, rumen metabolism, and N utilization. Diets contained (% of DM) the following proportions of alfalfa:corn silages, 50:0 (diet A), 37:13 (diet B), 23:27 (diet C), or 10:40 (diet D). All diets contained 26% NDF and contents of CP were 17.8% (diet A), 17.0% (diet B), 16.5% (diet C), and 15.7% (diet D). DMI decreased linearly (P<0.001) across diets with the lowest intake observed on diet D. Milk yield had both linear (P=0.02) and quadratic (P=0.04) effects and again diet D was lowest. Fat yield decreased linearly (P=0.001) with diet A differing from diets C and D. Protein yield was similar across diets but a quadratic effect (P=0.03) was observed. Total urinary N excretion, ruminal NH3, and total AA decreased linearly (P=0.002, P<0.001, and P=0.004, respectively) and in all cases diet D was the lowest. Ruminal pH and propionate were not different. However, ruminal acetate and acetate:propionate decreased linearly from diet A to D (P<0.001). Overall, diet D was associated with the poorest production although it yielded better N utilization.