Pupillary dilation as a thermal stress indicator in boer crossbred goats maintained in a climate chamber

Goats are homeothermic animals considered rustic from the bioclimatic point of view, but a reduction in their productive efficiency occurs under unfavorable thermal conditions. The present study evaluated pupil dilation as an indicator of thermal stress in Boer crossbred goats maintained under controlled environmental conditions. Six male crossbred goats of the Boer breed were distributed in a completely randomized design and submitted to temperatures of 26, 29 and 33 °C and 68% relative humidity. Pupillary dilation (PD), pupillary temperature (PT), respiratory frequency (FR), heart rate (HR), surface and rectal temperatures (ST and RT), body weight gain (BWG) and feed conversion (FC) were monitored. An increase in the PD of the animals was observed with elevated air temperature. Specifically, pupillary area increased by 26.96 mm2 at 33 °C compared to 26 °C. PD is shown as an efficient response for measuring the level of thermal stress in goats.