Changes in plasma cortisol and β-endorphin concentrations and behaviour in sheep subjected to a change of environment

Abstract

Changes in plasma cortisol and B-endorphin concentrations and behaviour in sheep subjected to a change in environment have been studied. Three male and three female sheep were transferred from pasture to indoor crates for a 9-week period. Behaviour was observed by scan sampling for 1-h periods morning and afternoon 5 days/week. Blood samples were taken hourly for 24-h periods on days 1, 5, 30 and 60, and assayed for β-endorphin and cortisol. Plasma cortisol concentration decreased significantly between days 30 and 60 (P < 0·001) but there was no significant change in plasma B-endorphin concentration over the experimental period. After an initial period of ‘withdrawal’ in weeks 2 and 3, when the amount of time spent resting increased, the occurrence of active behaviours increased with length of confinement. The results suggest that animals had not fully acclimatized to the new surroundings within the 9-week period. This raises important welfare issues concerning experimental animals.