Renal efficiency underlies adaptive heterothermy of heat-stressed hypohydrated goats.

Abstract

We investigated the thermotolerance of the F1 progeny (Black Bedouin × Damascus crossbreed) to summer conditions alongside that of two pure breeds. Male goats (n = 7 per breed) were used to conduct a summertime 28-day trial along with hypohydration. The animals were fitted with miniscule thermologgers, intraperitoneally and subcutaneously, to measure core (Tc) and peripheral (Tp) body temperatures (BT), respectively. All goats were kept under shaded housing for a 7-day basal period before being switched to unshaded pens for the next 21days. During the first 14days, animals had free access to water. However, during the third 7-day period, access to water was time-restricted (4h/day). Finally, it was restricted to 40% of the third week's average daily intake over the last 7days. Exposure to the unshaded conditions resulted in pronounced heat stress in all animals, as reflected by 0.42 and 1.44°C rises for Tc and Tp, respectively. The F1 goats displayed a clear heterothermic adaptive response, especially after the water restriction bouts' initiation. Interestingly, the F1 goats displayed higher ratios of renal relative medullary thickness (77.7, 73.3, and 72.6 ± 1.1%) along with higher circulating concentrations of antidiuretic hormone (44.6, 31.6, and 11.6 ± 3.7ng/mL), respectively, which suggested an improved water metabolism.