Plasma Glucose and Acetate and Milk Secretion in the Ruminant

Abstract

Tracer studies (1,3) have indicated that both glucose and acetate are important sources of energy for the lactating mammary gland in the ruminant. However, investigations with the isolated, perfused mammary gland of the goat (4) have shown that when glucose is omitted from the perfusion fluid, milk secretion ceases; whereas, in the absence of acetate only fat secretion is notably depressed. The importance of plasma glucose for the maintenance of milk secretion has been established in the intact animal also. In the lactating goat (2) and cow (9), administration of insulin causes a marked depression in milk yield and in milk lactose content. Kronfeld et al. (8) demonstrated that the effects are due to hypoglycaemia and not to a direct effect of insulin on the mammary gland, since they observed no reduction in the yield of milk when insulin and glucose were given simultaneously and a normal blood glucose concentration maintained.