Minimal Number of Conspecifics Needed to Minimize the Stress Response of Isolated Mature Ewes

Abstract

The objective of this study was to determine the minimum number of conspecifics that sheep require to minimize the stress associated with isolation from the flock. The study used twelve 3-year-old Suffolk ewes. Every test day the study randomly chose 1, 2, or 3 ewes to be visually separated from the flock for 20 min in a familiar pen, 20 m distance from their original pen. One of the ewes that remained in the flock was randomly chosen as a control. The dependent variables measured were number of steps, serum cortisol levels, body temperature, and heart and respiration rates before and after the 20 min isolation test. The study also recorded number of vocalizations and urinations. Results show that individual separation induced significant increases in respiration rate (p < .01), serum cortisol concentration (p < .01), number of steps (p < .01), vocalizations (p < .01), and urinations (p < .05). This effect declined to basal levels (control ewes) when a single companion ewe was present. There were no additionally significant (p > .05) advantages to having 2 companion ewes. The results indicate that the welfare of ewes is improved if they are separated from the flock in groups of at least 2 members.