Milk yield in rats in relation to activity and size of the mammary secretory cell population

Abstract

An attempt was made to partition changes in milk yield during lactation in the rat between changes in the size of the secretory cell population and changes in cellular activity. Groups of rats were studied ond 2, 7, 14, 21 and 28 of lactation. Milk yield increased betweend 2 and 7, less markedly betweend 7 and 14 and decreased betweend 14 and 21. Milk secretion had apparently ceased ond 28. Total mammary DNA (DNAt) and RNA (RNAt) increased fromd 2 to 14. It is concluded that of the increase in milk yield betweend 2 and 14, an increase in cell population accounted for 75 % and an increase in cellular activity for 25 %. A decrease in activity appeared to be entirely responsible for the decrease in yield betweend 14 and 21. © 1984, Proprietors of Journal of Dairy Research 1984. All rights reserved.