Effects of Feeding Raw Soybeans on Rumen Metabolism and Milk Composition of Dairy Cows

Abstract

Four rumen-fistulated Holstein cows were used in a three-period reversal feeding trial to determine the effects of feeding raw soybeans on milk yield, gross composition of milk, component fatty acids of milk fat, free fatty acids of milk, and volatile fatty acids and long chain fatty acids of rumen fluid. No problems in feed intake or health of cows were observed when ground ear corn and crushed soybeans were combined in a ratio of 3:1 and fed twice daily at National Research Council's recommended levels.When compared with a ground ear cornsoybean oil meal mixture the soybean ration was equivalent for milk production. Differences in gross composition of milk were not significant, though there was a consistant increase in milk fat with the raw soybean ration. This ration significantly increased the C18 acids in milk fat and decreased the C14 and C16 acids. Feeding raw soybeans did not appear to alter rumen fatty acid production, but caused significant increases in the levels of stearic and oleic acids in the rumen fluid. Stearic acid content of free fatty acids of milk also was significantly increased. Milk from each treatment was acceptable for flavor.