Effects of handling, shearing and previous exposure to shearing on cortisol and β-endorphin responses in ewes

Abstract

The objectives of the study were to compare the effects of handling and shearing on plasma cortisol and β-endorphin levels of ewes and to determine if adaptation to annual shearing occurred. Plasma cortisol and β-endorphin concentrations were determined during either handling only or handling plus shearing in 12 ewes previously exposed to annual shearing (1-4 times) and in 12 naïve ewes. The handling process consisted of four steps: 1) moving ewes from their quarters into the shearing room; 2) moving them in groups of four into a holding pen; 3) moving them in pairs to a shearing platform where they were up-ended and restrained as in shearing; and 4) moving them into another holding pen in the shearing room. Half of the ewes were sheared during step 3 of the handling process. Handling and shearing elevated (P < 0.0001) plasma cortisol and β-endorphin concentrations, but the responses to the handling process and to the handling plus shearing process were similar (P > 0.1). Moving the ewes from their quarters to the shearing platform resulted in significantly higher plasma cortisol, which remained elevated for 60 min. Plasma β-endorphin was only transiently elevated after shearing was completed. Previous exposure to shearing enhanced the cortisol (P < 0.001) and β-endorphin (P < 0.05) responses to handling and shearing. Both responses were significantly greater and longer in the ewes sheared previously. The results indicate that the stress response to handling was equivalent to that of handling plus shearing, and that the stress response was much greater in ewes previously exposed to annual shearing.