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Cold-induced inhibition of thermal panting in shorn sheep. 1. Effect of intensity of cold exposure

Published online by Cambridge University Press:  02 September 2010

J. Slee
J. Slee
Affiliation:
ARC Animal Breeding Research Organisation, West Mains Road, Edinburgh EH9 3JQ
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Summary

The delayed onset of heat-induced panting (at 42°C) immediately following previous shearing and exposure to cold was studied in 54 Scottish Blackface and 53 Tasmanian Merino sheep.

In control sheep (not previously cold-exposed) thermal panting commenced in 15 min. In cold-treated sheep, when the cold was intensified stepwise from +26°C (+30cC being thermoneutral) down to −10°C, using 2-hr exposures, or lengthened from 2 hr to 16 hr at +8°C, the delay (block) to panting increased non-linearly from 40 to 70 min.

The minimum intensity of cold required to produce a block (26°C in Merinos, 22°C in Blackfaces) was similar to that inducing peripheral vasoconstriction. More intense vasoconstriction preceded longer blocks, but vasoconstriction sometimes occurred without a subsequent block.

Merinos were more sensitive than Blackfaces to the blocking effects of cold, and, once blocked, the effect in Merinos was less easily removed by re-warming.

The time taken for cancellation of the heat debt during heat stress could account for half the block. The remainder, a delay of about 30 min, was attributed to a specific inhibition of respiratory control in the central nervous system.

Type
Research Article
Information
Animal Production , Volume 16 , Issue 3 , June 1973 , pp. 271 - 283
Copyright
Copyright © British Society of Animal Science 1973

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References

REFERENCES

Bazett, H. C. 1949. The regulation of body temperatures. In The Physiology of Heat Regulation, Chap. 4. Saunders, Philadelphia.Google Scholar
Blaxter, K. L., Graham, N. McC. and Wainman, F. W. 1959. Environmental temperature, energy metabolism and heat regulation in sheep. III. The metabolism and thermal exchanges of sheep with fleeces. J. agric. Sci., Camb. 52: 41–49.CrossRefGoogle Scholar
Bligh, J. 1963. Inhibition of thermal polypnoea in the closely shorn sheep. J. Physiol., Lond. 168: 764–781.CrossRefGoogle ScholarPubMed
Burton, A. C. and Edholm, O. G. 1955. In Man in a Cold Environment, pp. 38–41. Arnold, London.Google Scholar
Hardy, J. D. and Dubois, E. F. 1938. Basal metabolism, radiation, convection and evaporation at temperatures from 22° to 35°C. J. Nutr. 15: 477–492.CrossRefGoogle Scholar
Joyce, J. P. and Blaxter, K. L. 1964. The effect of air movement, air temperature and infrared radiation on the energy requirements of sheep. Br. J. Nutr. 18: 5–27.CrossRefGoogle ScholarPubMed
Maskrey, M. 1970. A comparison of the effects of close-shearing and of injections of noradrenaline into a lateral cerebral ventricle in the Welsh Mountain sheep. J. Physiol., Lond. 210: 102P.Google ScholarPubMed
Mitchell, D. and Wyndham, C. H. 1969. Comparison of weighting formulas for calculating mean skin temperature. J. appl. Physiol. 26: 616–622.CrossRefGoogle ScholarPubMed
Phillips, G. D. and Raghavan, G. V. 1970a. Responses of unshorn and shorn sheep to thermal stress. J. Physiol. Lond. 208: 317–328.CrossRefGoogle Scholar
Phillips, G. D. and Raghavan, G. V. 1970b. Role of naso-buccal passages in thermo-regulation in sheep. J. Physiol. Lond. 208: 329–337.CrossRefGoogle Scholar
Phillips, G. D. and Raghavan, G. V. 1970. Reflex onset of polypnoea in sheep. J. Physiol. Lond. 208: 339–352.CrossRefGoogle ScholarPubMed
Rawson, R. O. and Quick, K. P. 1970. Evidence of deep body thermoreceptor response to intra-abdominal heating of the ewe. J. appl. Physiol. 28: 813–820.CrossRefGoogle ScholarPubMed
Richards, S. A. 1970. The biology and comparative physiology of thermal panting. Biol.Rev. 45: 223–264.CrossRefGoogle ScholarPubMed
Slee, J. 1964. Comparative responses of Tasmanian Merino and Scottish Blackface sheep to a falling environmental temperature. Proc. Aust. Soc. Anim. Prod. V: 188–189.Google Scholar
Slee, J. 1968. Body temperature and vasomotor responses in Scottish Blackface and Tasmanian Merino sheep subjected to slow cooling. Anim. Prod. 10: 265–282.Google Scholar
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: 17–35.CrossRefGoogle Scholar