STUDIES ON THE HORMONAL INDUCTION OF MAMMARY GROWTH AND LACTATION IN THE GOAT

Extensive morphological and functional investigations have been carried out on the artificial induction of mammary development and lactation in the goat using hexoestrol alone and in combination with progesterone, at several dose levels and proportions. Administration of the oestrogen and progesterone was either by tablet implantation or by subcutaneous injection in oily solution. Forty animals were used, of which twenty-three were ovariectomized during infancy. Special histological techniques were devised for studying and estimating quantitatively the degree of mammary development. In the later experiments this was achieved by surgically removing one half of the udder, i.e. one gland, when the lactation curve had reached a maximum. In three normally lactating goats the operation had no influence on the milk yield of the remaining gland. For the dose levels used, the milk yields of the animals receiving oestrogen and those receiving oestrogen and progesterone did not differ significantly. In general, the artificially induced milk yields were below the expected yields had the animals come into lactation after kidding. It appeared highly probable that the total area of secretory epithelium in the artificially developed gland was less than in the normally developed udder. A high correlation was observed between the surface area of the secretory epithelium in the entire half udder and the milk yield. Several marked abnormalities were observed in the microscopic structure of the udders. These were less evident in the glands of the goats receiving progesterone provided the oestrogen dose was not excessive.