Mammary extraction of plasma triglycerides in the cow during lactogenesis

1. In control cows, extraction of triglycerides from the circulation by the mammary gland increased abruptly and markedly, and the concentration of triglycerides in arterial plasma fell, on the day of parturition. 2. In cows that had fluid regularly removed from the mammary glands before parturition, these changes occurred at varying times from more than 4 days before parturition in an animal that secreted triglyceride copiously to 24 hr before parturition in an animal that secreted little triglyceride pre-partum. 3. In all animals, the time when triglyceride extraction increased was close to the time when K+ concentration in the mammary secretion became maximal.