The response of lactating dairy cows to increasing levels of whole roasted soybeans.

Twenty-four Holstein cows, including four primiparous and four ruminally cannulated, were in replicated 4 x 4 Latin squares with 21-d periods to determine the effects of feeding level of whole roasted soybeans on lactation performance and rumen function. Cows were fed rations containing a 50:50 forage:concentrate ratio with 0, 12, 18, or 24% of diet DM as whole roasted soybeans. Rations contained 16.8, 16.9, 18.6, and 19.7% CP and 1.68, 1.71, 1.72, and 1.74 Mcal NEL/kg DM, respectively. Milk production and milk fat percentages for diets containing 0, 12, 18, or 24% whole roasted soybeans were 34.9, 37.5, 38.5, and 38.8 kg/d and 3.23, 3.20, 3.32, and 3.37%, respectively. Milk protein percentage was depressed at all levels of whole roasted soybeans. Ruminal pH, VFA molar percentages except valerate, and DM disappearance of forage from dacron bags did not differ among treatments. Responses were similar among primiparous and multiparous cows. Results suggest benefit from feeding whole roasted soybeans at levels up to 18% of ration DM without adversely affecting DMI, milk fat, or rumen fermentation.