PUPILOMETRIA COMO INDICADOR NÃO INVASIVO DE ESTRESSE TÉRMICO EM OVELHAS

Abstract

The aim of this study was to evaluate pupillometry as a technique for detecting heat stress in sheep under controlled environmental conditions. Six crossbred Santa Inês × Dorper ewes, approximately 7 months old and with an initial body weight of 23.70 ± 5.73 kg (mean ± SD), were assigned to a completely randomized design with repeated measures and exposed to three controlled air temperature conditions (26, 29, and 34 °C; 65% relative humidity) in a climatic chamber under standardized lighting. Pupillary area (PA) was obtained from video recordings by extracting images and processing them manually for analysis. Thermoregulatory responses, including respiratory rate (RR), heart rate (HR), and cortisol, among others, were also evaluated. Means were compared using Tukey’s test, and associations were assessed using Pearson’s correlation (P ≤ 0.05). PA increased by 16.05 mm² (≈20%) between 26 and 34 °C. RR and HR increased progressively across 26, 29, and 34 °C (P < 0.001), while cortisol increased by approximately 66% (P = 0.01). Strong positive correlations were observed between PA and RR (r = 0.88), HR (r = 0.87), and cortisol (r = 0.84). In conclusion, pupillary dynamics are associated with thermoregulatory responses in ewes exposed to heat stress, highlighting the potential of pupillometry in production animals. However, further research is needed to develop technological solutions that enable practical on-farm applications.