Mammary gland development in gilts

Abstract

Mammary development was measured in gilts from birth to day 112 of pregnancy. Non-pregnant gilts were slaughtered at age intervals of approximately 10 days and pregnant gilts were slaughtered at pregnancy stage intervals of approximately 10 days. Before pregnancy, accumulation of mammary tissue and DNA was slow until approximately 90 days of age. The rate of mammary tissue and DNA accretion then increased four- to sixfold. In pregnant gilts, almost all accumulation of mammary tissue and DNA occurred in the last third of pregnancy. The accumulation seemed to continue until term. The measurement of labelled mammary epithelial cells after an in vivo injection of the thymidine analogue bromodeoxyuridine could not detect small or moderate changes in the rate of mammary DNA accumulation. We conclude that mammary gland development in gilts appears to occur in phases with varying rates of mammary growth.