Thermoregulatory response of goat kids subjected to heat stress

A study was conducted to evaluate the effect of shade (SHD) deprivation on the thermo-physiological response in goat kids. Seven Damascus kids were exposed to daytime solar radiation (SUN; days 0–20), after an initial 7-day SHD period. Another group (n = 7) was maintained under a SHD regimen throughout the 28-day observation period. Daily measurements (06:00; 12:00; 19:00) included respiratory rate (RR), heart rate (HR), and temperature of the skin (Tskin), hair coat (Tcoat) and rectum (Trec). Meteorological measurements indicated a greater heat load during the SUN treatment, compared to SHD. Compared to SHD, the SUN treatment caused a 21.3 and 9.2% increase in Tcoat and Tskin, respectively, at 12:00 for a period of 19–21 days. Furthermore, RR, HR and Trec were higher following the SUN treatment, compared to their SHD counterparts by 133, 12, and 1.5%, respectively, for a period of 10–14 days (12:00)—followed by a gradual adaptation to the chronic heat stress. There was a lag of 2–3 days before an increase in nighttime RR, HR and Trec after initiation of the SUN treatment—due to the change in day to nighttime feeding. The SUN Trec and Tskin recorded a significant decrease at 06:00 during the last 8–10 days of the trial, compared to the SHD-group, with a mean of 0.3 and 1.4 °C, respectively. The goats acquired homeothermy following chronic exposure to solar heat via harmonized thermoregulatory mechanisms, e.g. the adjustment of respiratory evaporative cooling and blood redistribution and a subsequent increase in the peripheral blood flow with a modification in feeding and water intake patterns. Accessibility of goats to shade during summer is a simple and yet an efficient tool to minimize solar radiation-induced heat stress.