J. Anim Sci.
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J. Anim Sci. 1976. 42:608-615.
© 1976 American Society of Animal Science
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Relation of High Temperature Regimes to Energy Metabolism, Body Composition and Feed and Water Intake in Rats

W. S. Alhassan1,3,, J. G. Buchanan-Smith1 and G. C. Ashton2,4,

University of Guelph, Guelph, Ontario, Canada, N1G 2W1

Abstract

Weanling rats were exposed to one of three temperature regimes: control (C) 21.1 C continuously, hot (H) 29.4 C continuously and modified-hot (MH) 29.4 C for 7 hr followed by 21.1 C for 17 hr each day, for a 14-day acclimatization period followed by a comparative slaughter trial. For the latter, 25 rats exposed to each temperature regime were killed initially and 45 other rats were individually fed one diet, at one of five intake levels — ad libitum and 20, 40, 60 and 80% of the ad libitum intake, for 28 days and then killed. Dry matter intake, rate of live weight gain and energy retention were depressed (P = .05) by the H vs MH and C regimes as well as by the MH vs C regime. It was apparent that the exposure of MH rats to cooler temperature each day provided considerably relief from the depressing effects of heat. Fasting heat production, kcal/W.75kg/day, was less (P = .05) for H-exposed rats, 42.6, as opposed to MH-, 75.9 and C-, 83.6 but efficiencies of MEn utilization above maintenance were similar (P = .05) for rats in the three temperature regimes. Regression analyses revealed that increasing temperature and dry matter intake were both associated with increasing proportions of fat and decreasing proportions of ash and protein in the empty body. It was also revealed, when dry matter intake was constant, that higher temperature was associated with a greater rate of live weight gain, energy retention and a greater efficiency of MEn utilization. These results illustrate the significance of depressed dry matter intake in limiting productivity of animals exposed to hot temperatures.

Footnotes

1 Department of Animal and Poultry Science.

2 Department of Mathematics and Statistics.

3 Present address, Department of Animal Production, University of Science and Technology, Kumasi, Ghana.

4 Research reported is from the senior author's Doctoral dissertation. The authors acknowledge the Ontario Ministry of Agriculture and Food for financial assistance, G. C. Smith for technical assistance, and W. N. Garrett, University of California for helpful suggestions.






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Copyright © 1976 by the American Society of Animal Science.