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Calorigenesis of Cattle as Influenced by Growth Hormone and Environmental Temperature¹

University of Missouri, Columbia

Abstract

Four Holstein cows were used to determine the influence of growth hormone on calorigenesis at 18 and 38° C. The objective of the study was to determine the calorigenic action, latent period, biological effective time and peak metabolic response of growth hormone at different environmental temperatures. The injection of GH at 18 and at 38° C. increased resting or standing metabolism and pulse rate. The latent period was 10 hr. at 18° C. and 4 hr. at 38° C. The biological effective time was 40 and 50 hr. at the comfort zone (18° C.) and under exposure to heat, respectively. Growth hormone increased thyroid activity and decreased the RQ. These results suggest that the calorigenic action of GH may be due to a synergetic reaction with thyroxine or to the increase in fat metabolism. High temperature (38° C.) decreased pulse rate, oxygen consumption and feed intake and increased respiration rate and rectal temperature, indicating a serious disturbance in thermal equilibrium.

¹ Contribution from the Missouri Agricultural Experiment Station, Journal Series No. 3097. Approved by the Director.

² Department of Dairy Husbandry.

³ The growth hormone (bovine) was kindly supplied as a gift by Endocrinology Study Section, National Institutes of Health, Bethesda, Maryland.