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Cold Exposure of Southdown and Welsh Mountain Sheep. 2. Effects of breed, plane of nutrition and previous acclimatization to cold upon skin temperature, heart rate, shivering and respiration rate

  • A. R. Sykes (a1) and J. Slee (a1)
Summary
SUMMARY

Shorn Southdown and Welsh Mountain sheep on high or maintenance levels of nutrition were subjected to two acute (−20°C; 4 mph wind) cold exposures in climate chambers. Before and between exposures the sheep were kept in either a cold (+8°C) or a thermoneutral (+30°C) environment.

1. At +8°C, all the sheep shivered and showed sustained vasoconstriction and elevated heart rates.

2. At + 30°C, heart rates, skin temperatures on the extremities and muscular tone were all consistently higher in sheep which had previously been kept at +8°C.

3. During cooling, the onset of vasoconstriction and increase in heart rate were both delayed in sheep previously kept at + 8°C.

4. These effects (2, 3) were retained for at least 2 days but less than 12 days after the sheep returned to thermoneutrality. They decayed faster than the increased resistance to body cooling produced simultaneously in the same sheep (Sykes and Slee, 1969), since this was still detectable after 2 weeks.

5. Breed differences were mainly small.

6. It was concluded that acclimatization induced by chronic cold exposure was associated with a temporary increase in basal metabolic rate.

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References
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Joyce J. P. and Blaxter K. L. 1964. Effect of air movement, air temperature and infrared radiation on the energy requirements of sheep. Br. J. Nutr. 18: 527.
Riek R. F., Hardy M. H., Lee D. H. K. and Carter H. B. 1951. The effect of the dietary plane upon the reactions of two breeds of sheep during short exposures to a hot environment. Aust. J. agric. Res. 1: 217230.
Slee J. 1968. Body temperature and vasomotor responses in Scottish Blackface and Tasmanian Merino sheep subjected to slow cooling. Anim. Prod. 10: 265282.
Slee J. and Sykes A. R. 1967. Acclimatization of Scottish Blackface sheep to cold. 1. Rectal temperature responses. Anim. Prod. 9: 333347.
Swift R. W. 1932. The influence of shivering, subcutaneous fat and skin temperatures on heat production. J. Nutr. 5: 227249.
Sykes A. R. and Slee J. 1968. Acclimatization of Scottish Blackface sheep to cold. 2. Skin temperature, heart rate, respiration rate, shivering intensity and skinfold thickness. Anim. Prod. 10: 1735.
Sykes A. R. and Slee J. 1969. Cold exposure of Southdown and Welsh Mountain sheep. 1. Effects of breed, plane of nutrition and acclimatization to cold upon resistance to body cooling. Anim. Prod. 11: 6575.
Webster A. J. F. 1967. Continuous measurement of heart rate as an indicator of the energy expenditure of sheep. Br. J. Nutr. 21: 769785.
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Animal Science
  • ISSN: 1357-7298
  • EISSN: 1748-748X
  • URL: /core/journals/animal-science
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