Effects of intravenous infusions of acetate, beta-hydroxybutyrate, triglyceride and other metabolites on the composition of the milk fat and blood in cows.

1. The effects in the cow of intravenous infusions of sodium acetate, butyrate, propionate, beta-hydroxybutyrate, malonate, citrate or succinate, of glucose or of an emulsion of cottonseed oil on the secretion of the component fatty acids of milk fat and on the composition of the blood plasma of the jugular vein have been studied. 2. Glucose and cottonseed oil were the only metabolities consistently to affect the yield of milk fat. Glucose decreased the yield of milk fat through a diminished secretion of the C(18) fatty acids and in two out of three cows also of the steam-volatile fatty acids (C(4)-C(10)). The cottonseed oil caused an increase in the yield of milk fat through an increased secretion of linoleic acid, the major component acid of the cottonseed oil. In three out of four cows, acetate caused an increase in the yield of milk fat through an increased secretion of mainly palmitic acid. 3. The effects of the infusions on milk-fat secretion are discussed in relation to existing knowledge on the origin of the fatty acids of milk fat.