Short and long-term thermoregulatory, metabolic, and stress responses to winter shearing in rams.

Abstract

The aim of this study was to characterize the thermoregulatory, metabolic, and stress responses of rams to winter shearing, with a focus on both short-term and long-term effects. Eleven rams were sheared in mid-winter in a humid subtropical climate, according to the Köppen climate classification (environmental temperature and humidity during the study: 10.3 ± 3.6 °C and 77.7 ± 16.7%, respectively). Meanwhile, another 11 rams served as non-sheared controls. Immediately after shearing, rams increased their blood cortisol concentration, glycemia, hematocrit, and heart rate. Wool removal quickly reduced the surface temperatures at the base of the ear, nose, and lips, but did not affect rectal temperature. During the days following shearing, heart rate, glycemia, hematocrit, and blood concentrations of triiodothyronine and total protein increased. These changes were accompanied by a decrease in the surface temperatures of the eye and the base of the ear, but the rectal temperature remained unchanged. During the 11 days after shearing, rams were observed walking and standing more frequently, displaying increased agonistic interactions, and spending less time lying down. In conclusion, rams exhibited a typical acute stress response immediately after shearing, characterized by thermoregulatory and metabolic changes that persisted for several days. Rams modified their behavioral pattern, increasing thermogenesis and reducing heat loss. Sheared rams displayed an effective heat redistribution, maintaining their core temperature. Rams also increased their aggressiveness, which requires careful management to reduce the risk of injuries.