A Study of the Influence of Thyroxin on Milk Secretion

Abstract

A knowledge of the physiological factors affecting milk secretion is essential to the study of the causes of variation in milk yield among dairy cows. It is reasonable to suppose that the activity of the mammary gland is a direct function of the general metabolism of the animal. If this supposition is correct, those factors that affect the metabolism should have a similar influence on milk yield. The stimulating effect of thyroxin and thryoid extracts upon the metabolic rate of animals has been well estabfished Henderson (9) has studied the effects of variou~ stimulants and galactogogues over two day test periods, lVicCandlish (13, 14) studied the effect of drug administration on milk yield in a two day period. Ott and Scott (15, 16) injected animal extracts and observed the number of drops of milk secreted in a five minute period following injection. Changes brought about by the various treatments were not significantly large or of long enough duration that the data could be applied to the study of the problem of milk secretion.