Physical and psychological stressors are known to cause a transient increase in the core body temperature of mammals. We hypothesized that rise in core body temperature could be used to indicate the intensity of stress experienced by sheep. Based on established indices of stress, we ranked five treatments from very low to severe stress as follows: Holding with flock mates, Human presence, Visual isolation, Capture and inversion, and Simulated shearing. Change in core body temperature was measured remotely using thermal sensors placed in the ear canal of the sheep. Maximum change in core body temperature (p=0.08) and the area under the core temperature change curve (p=0.09) allowed differentiation of the least and most stressful treatments: Holding with flock mates and Simulated shearing. The intermediate treatments could not be differentiated using change in ear canal temperature. Therefore, given the levels of statistical significance, our hypothesis that stressors of different intensities could be discriminated by changes in ear canal temperature was only partially supported. Reasons for the inability to discriminate between all treatments include a lack of sensitivity of change in ear canal temperature as an index of stress, high individual variability in responses to stress, and thermal sensor malfunction.
Proceedings of the New Zealand Society of Animal Production, Volume 64, Hamilton, 72-76, 2004
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