Search

CONTRIBUTIONS to the knowledge of the influence of reproduction, especially that of the individual reproductive hormones upon the growth rate in the female, have not been numerous. In most of these investigations the effects of ovariectomy or of pregnancy were generally studied. Evidence that ovariectomized rats grow more rapidly than virgin controls has been presented by Stotsenburg (1913), Slonaker (1930), Freudenberger and Billeter (1935), Freudenberger and Howard (1937), Freudenberger and Hashimoto (1937–38 and 1939) Bogart et al. (1940), and Tang (1941). Pronounced differences in the rate of growth were shown to exist between pregnant and virgin female rats of the same age by Slonaker (1927), Cole and Hart (1938) and Bogart et al. (1940). The effects of pregnancy, pseudopregnancy (Hart and Cole, 1939) and ovariectomy upon growth indicate that the reproductive hormones may be directly or indirectly involved.

Published October 1951. Facts and recommendations in this publication may no longer be valid. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catalog

Summary and Conclusions1. Testosterone injected intramuscularly at the rate 1 mg/kg of body wt per week in beef heifers and steers from 500 to 800 lb live wt had the following effects: a) Increased average daily gain and decreased feed requirements per unit gain, b) Increased weight of the thyroid glands, c) Increased secretory activity of the thyroid gland, d) Decreased stores of thyroxine in the thyroid gland. 2. Correlations between thyroid gland activity and growth rate are suggested as indicating a possible mode of the action of testosterone in affecting growth of beef cattle. 3. A method is described using the time of asphyxiation of thiouracil-treated mice as a measure of thyroxine content of the thyroid gland.