Dilatação pupilar como indicador de estresse térmico em caprinos mestiços Boer mantidos em câmara climática.

Abstract

Goats are homeothermic animals considered to be rustic from the bioclimatic point of view, but in unfavorable thermal conditions the reduction of their productive efficiency occurs due to the need of the activation and maintenance of thermoregulatory mechanisms. The present study was carried out to evaluate pupil dilation as an indicator of thermal stress in Boer crossbred goats maintained under controlled environmental conditions (climatic chamber). Six male crossbred goats of the Boer breed were evaluated, distributed in a completely randomized design submitted to temperatures of 26, 29 and 33 °C and relative humidity of 68%. The pupillary dilation (PD) and pupillary temperature (PT), Respiratory Frequency (FR), Heart Rate (HR), Surface and Rectal Temperatures (ST and RT), Weight Gain (WG) and Feed Conversion (FC) were monitored. It was observed the increase of the PD of the animals with the elevation of the air temperature, observing an increase of 26.96 mm² pupillary area when comparing the temperatures of 26 and 33 °C. The increase in PT, RF, HR, ST and RT, as well as the decrease in WG and FC, occurred in response to the increase in air temperature. PD is shown as an efficient response to measure the level of thermal stress to which goats are subjected.