Release of cholesteryl esters by the mammary gland of the pre-partum cow.

In five cows that were regularly milked before parturition, cholesteryl esters were continuously released into the mammary fluid; their concentration in the fluid was initially high, but decreased a few days before parturition when mammary secretion of fluid and triglyceride was increasing. The composition of fatty acids in the cholesteryl esters of mammary fluid and in blood plasma was different, suggesting mammary synthesis of cholesteryl esters.