Synthesis of Milk Fat in the Bovine Mammary Gland

Abstract

Milk fat synthesis was studied in normal lactating dairy cows following the intramammary infusion of C14-labeled glycerol, glucose, acetate, propionate and butyrate. The metabolite under investigation was infused into one quarter (or half) of the udder and a comparison was made of the C14 content of milk fat glycerol obtained from the infused and uninfused quarters. The results indicate that glycerol is synthesized in the mammary gland from glucose but not from acetate, propionate or butyrate. Further, it was shown that the newly formed glycerol is incorporated into milk fat. This strongly implies that one pathway of milk fat formation involves its de novo synthesis in the mammary gland from "pools" of free fatty acids and glycerol.