Influence of Dietary Cottonseed and Soybean on Milk Production and Composition

Abstract

Eight rumen cannulated Holstein cows were used in two 4×4 Latin squares to study the factors involved in depression of milk protein synthesis when whole soybeans or cottonseeds are fed. Supplements fed in each square were oilseed meal, oilseed meal plus oil, whole seeds, and roasted whole seeds. Diets contained 16.5% CP of which 40% was provided by the oil meal or oil seed. Milk yield was not affected by diet, but milk fat percent was reduced with addition of free oil. Milk protein and casein contents were lowered by feeding soy product with oil, but this was not observed with cottonseed. Feed consumption was reduced with inclusion of oil or whole seeds. Digestion in the total tract was reduced by free oil. The proportion of propionate in ruminal VFA was higher and that of butyrate lower as a result of feeding free oil. Protozoal numbers were reduced with free oil and whole seed but were not affected by addition of roasted oil seed. Free oil supplementation increased content of unsaturated long chain fatty acids in rumen fluid. The ratio of serum glucose to unsaturated long-chain fatty acids was positively correlated with percent milk protein. Concentrations of essential amino acids in blood plasma were reduced by feeding soybean oil products, and a similar but nonsignificant trend for this was observed with feeding of cottonseed oil products.