Physiological response of Katahdin ewes to the absence of shadows in tropical region of Mexico

Abstract

This study evaluated the effect of environmental conditions on the physiological and body infrared temperature traits of Katahdin sheep. Ten recently reproductive-managed ewes were randomly segregated into two groups. The control group (CG) was under outdoor conditions with shadow access, and the experimental group (EG) was under outdoor conditions without shadow access. Traits were measured for 16 days, and the environmental traits confirmed significant differences between groups, with an average temperature-humidity index (THI) of 68.64±1.46 for the CG and 72.98±3.17 for the EG, with a breach of five units between groups. The THI was subsequently used to evaluate the heat load. Respiratory frequency was the physiological variable that responded the most to heat stress. The rectal temperature of the sheep was greater in the experimental group than in the control group, indicating an increase in heat stress. The EG also presented higher heat emissions from body regions, which was associated with changes in core body temperature and blood flow at the body surface. Differences in hematological parameters, such as the erythrocyte count, mean corpuscular volume, and total plasma protein concentration, were found between the groups. Infrared thermography was found to be efficient for estimating heat stress in sheep species, and head temperature was found to be a reliable indicator of physiological thermal stress.