The Relation between the Initial Rise and the Subsequent Decline of Milk Secretion following Parturition

I t is a common observation of dairymen that the milk flow of the dairy cow rises for some time after calving and then declines steadily. In preceding papers 1 we have presented data and have offered an interpretation for the declining segment of the curve of milk secretion. Having found that after the first month of lactation the curve of milk secretion with the advance of the period of lactation may be represented by the exponential law representing the course of monomolecular change in chemistry, we suggested the interpretation that the course of milk secretion is wobably limited by a monomolecular chemical reaction. This interpretation seemed reasonable in view of the fact that milk secretion must be a chemical or physicochemical process since certain substances typical of blood are converted into other different substances typical of milk. The initial rise of milk secretion, on which no data were available at that time, was explained as due to the improving condition of the animal and to the increasing food consumption due to the improved condition. However, a comparison of the curve of food consumption with the curve of milk secretion does not show the expected parallelism, ~ and the condition of the animal appears to become normal within a short t ime after calving which is long before maximum milk secretion is reached. These facts suggest that under favorable conditions of food and management the factors limiting or controlling the characteristic rise and