Abstract
Summary
Lactogenic hormone was administered subcutaneously at 1, 2 or 3 mg to lactating rats each day during days 7 to 19. Milk yields were obtained after a 10-hour isolation period of dam from pups on days 14, 16, 18 and 20 of lactation. One mg of lactogenic hormone significantly increased yield on days 18 and 20; 2 mg on days 16, 18 and 20; and 3 mg on days 14, 16, 18 and 20. Maximum stimulation occurred on day 20 with 2 mg and 3 mg of hormone, with 88 and 82% increase over controls, respectively. Determination of deoxyribo- and ribo-nucleic acids of mammary glands from lac-tators sacrificed on day 20 revealed no significant increase in DNA but significant increases in RNA after hormone treatment. The data strongly suggest that maximal levels of litter weight size and mammary gland size are limiting in ability to estimate milk secretion potential, while milk yields and RNA values reflect secretory status beyond these limits. Lactogenic hormone at 2 or 3 mg per day stimulates increased lactation more than any other single hormone treatment attempted to date.
Get full access to this article
View all access options for this article.