SOME EFFECTS OF REPEATED HANDLING ON STRESS RESPONSES IN SHEEP

Repeated exposure to a handling treatment was investigated as a possible method of reducing the stress response to shearing. Sheep were exposed to sham shearing (a procedure in which no wool is removed, but which otherwise resembles shearing) on four occasions at two-week intervals. The peak cortisol response to this procedure was not affected, but concentrations of plasma cortisol declined more rapidly to lower baseline concentrations after four exposures. Basal haematocrit also declined over the four exposures. In contrast, adrenal responsiveness to exogenous adrenocorticotrophic hormone (ACTH) increased over the period of sham shearing. The response to sham shearing was unrelated to flight distance of sheep or their position in a forced movement order. Flight distances of sham-shorn sheep were significantly shorter than those of control sheep after the four exposures. There was no correlation between forced movement or competitive order before and after sham shearing. The stress response to sham shearing was only slightly reduced by repetition, although the response apparently remained sufficient to affect adrenal responsiveness. © 1990.