Studies on the hormonal induction of mammary growth and lactation in the goat. II. Functional and morphological studies of hormonally developed udders with special reference to the effect of 'triggering' doses of oestrogen.

Abstract

SUMMARY 1. Treatment of spayed virgin goats with oestrogen ('triggering'), following administration of oestrogen and progesterone for 150 days to cause udder development, had no significant effect on the milk yield or on the structure of their udders. 2. Daily injections of 0·5 mg hexoestrol plus 70 mg progesterone for 150 days with or without the final oestrogen 'triggering' treatment induced udders which were virtually free from histological abnormalities and in which the alveolar tissue was homogeneous and compact. The milk yields were reasonably uniform between goats, and the incidence and degree of asymmetry in milk yield between two halves of the udder were no greater than in normally lactating goats. 3. Treatment for 20 weeks with oestrogen alone at daily doses ranging from 0·025 to 0·25 mg grew glands characterized by histological abnormalities previously found in glands developed with higher doses of oestrogen, namely cystic alveoli, papillomatous outgrowths from the epithelium and immature lobules. There was no graded relationship between dose of oestrogen and milk yield, and asymmetry of yield between the two halves of an udder was marked and widespread, particularly in the goats receiving the lowest dose. 4. Total alveolar surface areas of half-udders removed at the peak of lactation were estimated by three related methods, all of which gave high correlations with the milk yields of these udder halves. With only one of these methods, however, was there an appreciable partial correlation between porosity index (surface area/unit volume) and milk yield.