EFFECTS OF VARIOUS ROUGHAGE SOURCES IN COMPLETE FEEDS ON MILK PRODUCTION, COMPOSITION AND RUMEN METABOLISM OF DAIRY COWS

Abstract

Twenty lactating cows were used over two growing seasons to compare three complete feeds containing corn silage, alfalfa grass silage or ground hay, with long hay as the control. The roughage to concentrate ratio was 6:4 in experiment 1, and 4:6 in experiment 2. There were no significant (P < 0.05) differences m dry matter and total digestible nutrient (TDN) intake among roughage sources except for corn silage in experiment 1. The molar percentage of acetic, butyric, valeric, isobutyric and isovaleric and the molar proportion of acetic to propionic were not affected (P < 0.05) by different sources of roughage. In experiment 1, TDN, dry matter, crude protein and nitrogen-free extract (NFE) digestibility was lower (P < 0.05) for the corn silage diet. However, in experiment 2 there were no significant differences (P < 0.05) in TDN, dry matter, crude protein and NFE digestibility among the experimental treatments. Blood glucose and urea concentrations were not affected by roughage sources. The mean daily (experiment 1) milk yields of cows fed long and ground hay mixtures were greater (P < 0.05) than those of cows fed the alfalfa grass silage mixture; however, the mean daily fat-corrected milk (FCM) yield was not affected (P < 0.05) by the source of roughage (experiment 1). The mean daily milk yield and FCM yield were not affected significantly (P < 0.05) by roughage source (experiment 2). The percentage of milk fat, and solids-not-fat, were not influenced (P < 0.05) by roughage source (experiments 1 and 2). Roughage source appeared to have little effect on molar ratios of fatty acids found in the milk fat.