Abstract
Summary
Groups of rats Received daily injections of 2 mg somatotropin (STH) from either day 3-19 of pregnancy or day 1-13 of lactation. Another group of rats Received graded increments (0.5-3.0 mg) of STH every 6 days during both pregnancy and lactation, Other groups of rats served as pregnancy and lactation controls. Mammary gland deoxyribonucleic acid (DNA) content was determined in all rats and milk yield was determined in all rats carried to day 14 postpartum. Significant increases in mammary DNA occurred in all rats treated with STH irrespective of dose or schedule of injections when compared to gestation controls. A significant elevation in mammary DNA above the lactation control level was also evident in rats receiving the hormone and carried to day 14 of lactation. Milk yield of rats treated with graded increments of STH was significantly greater than that of control lactators but milk yield of rats receiving a constant daily dose of the hormone did not differ from that of controls.
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