The Rate of Milk Secretion as Affected by an Accumulation of Milk in the Mammary Gland

Abstract

Summary 1.It was shown that the speed of milk secretion in unit time is governed by the amount of milk accumulated in the udder or the interval between milkings. If the amount of milk secreted during the first hour is called 100 per cent the amount of milk secreted each succeeding hour is approximately 95 per cent of that secreted during the preceding hour. 2.The curves showing the rate of milk secretion follow the same course as a chemical reaction when the products of the reaction are not removed indicating that milk secretion is a chemical process and follows the usual laws of physical chemistry. 3.Under the experimental conditions noted it was calculated that cows milked three times per day would produce 110 per cent and those milked four times per day 116 per cent of the milk secreted by cows milked twice daily. 4.The data indicates that the per cent of fat and total solids gradually decrease with the lengthening of the interval between milkings until the time interval exceeds fourteen to sixteen hours. Thereafter there is a slight increase up until the twenty-fourth to twenty-sixth hour, followed again by a gradual decline until the thirty-sixth hour.