Disproportionate thermophysiological strain between intensively- and extensively-managed goats during summer

Goat keeping is feasible for smallholder farmers in many world regions especially those best suited for extensive management. However, summertime grazing in arid zones entails major challenges to animal thermoregulation and well-being. An experiment was conducted to evaluate the thermoregulatory performance and selected hemogramic parameters in intensively (INT) or extensively (EXT) managed goat kids (N = 14). We applied a previously established technique to evaluate body thermal state of freely ranging animals, in which contemporaneous temperatures of the core (Tc) and periphery (Tp) are chronically recorded. Animals were initially kept for 12 days under INT management. Subsequently, seven animals were transferred to a grazing pasture and gradually transitioned over a four-day acclimatization period, then kept for the last 22 days under EXT conditions. Water drinking was limited to twice daily in both groups. Excessive solar radiation-induced heat load - with daytime black globe temperatures (Tbg) often exceeding 40 °C - under EXT was primarily responsible (r2 = 0.49; P < 0.05) for 0.57 and 1.72 °C rises in Tc and Tp, respectively, over INT kids. Unlike the typically biphasic pattern noticed for daily temperatures of both body sites in INT goats, that of EXT counterparts became rather polyphasic, whereby water drinking had drastic and prolonged thermolytic effect, inducing 0.40-0.41 and 0.79-1.45 °C declines in Tc and Tp, on midday and afternoon watering bouts, respectively. Despite indication for added daytime heat load, EXT goats displayed lower early morning Tc than INT. All animals exhibited hypohydration, as reflected by rises in hematocrit, serum osmolality, albumin, potassium, and sodium, being more pronounced in EXT conditions. Results emphasize the excessive thermophysiological strain facing grazing animals in arid zones during the summer.