Studies in milk secretion: I. The effect of nutrition on yield and composition

Abstract

I. As a result of withholding food for a few days, together with an injection of phloridzin, thereby reducing the nutrition, the daily yield of milk in goats was diminished and in one case the flow was actually stopped. On giving food again the yield returned almost to normal within a few days. II. As the daily yield of milk diminished under these conditions so the percentage of fat in the milk rose. Limitation of the available nutriment in the body (change from a high to low state of nutrition) did not reduce the percentage of lactose or protein in the milk (Paton and Cathcart) but reduced the quantity of milk (together with the amounts of protein, sugar and salts) produced. The secretion of fat was not at first affected by the change in metabolism and as a consequence milk rich in fat was produced. III. The amount of fat secreted per day under these conditions of diminishing yield was however not constant but became reduced, possibly as a secondary effect of the decreased secretion taking place in the gland cells. IV. On again giving food to animals in such a reduced state of nutrition, the percentage of fat in the milk decreased as the yield increased, in some cases to such an extent that it was below that of the normal milk before the experiment began.