Responses of simultaneously recorded intraperitoneal and subcutaneous temperatures of Black Bedouin goats to transient thyrosuppression during cold stress

Unlike poikilotherms, homeotherms resist wide amplitudes of core body temperature (T_core) fluctuation when exposed to reasonably variant ambient temperature (T_a) extremes. The degree of cold/heat thermotolerance varies tremendously amongst mammalian species. Thermotolerance can be partially inferred by the extent of resistance in body temperature displacement from normothermia when subjected to thermal stress. Regulation of thyroid calorigenic hormones is primarily contingent upon thermal homeostasis. Thyrosuppression generally exacerbates cold stress and hence may be a useful tool to examine the extent of cold-tolerance. An experiment was conducted to examine the extent of cold-tolerance on artificially goitrous Black Bedouin goats. Ten goat kids (initial Avg. BW = 30.6 ± 0.4 kg) were fitted with two miniature temperature data loggers, intraperitoneally and subcutaneously to identify core (T_core) and subcutaneous (T_sq) temperature responses, respectively, to chronically (47 days) cold (< 10 °C) environment along with or without oral administration of the thyreostat propylthiouracil (PTU 20 mg/kg BW/day). Five animals served as controls (CON) whereas the remaining five were treated with PTU for 31 out of the overall 47-day observation period. Despite its 74.5%-evoked transient depression of circulating free thyroxine (FT4), PTU-treatment failed (P > 0.10) to cause significant displacements in T_core or T_sq as compared to CON values throughout the 52-day trial period. As a function of T_a, T_core ? T_sq thermal gradient revealed a significantly (P < 0.01) linear regression (r² = 0.41), to indirectly infer a graded blood redistribution from peripheral to splanchnic vascular beds with the fall in T_a. In the light of the current findings, it can be deduced that– in addition to the fact that it is superior in terms of heat-tolerance– the Black Bedouin goat is also profoundly cold-tolerant. Furthermore, our recently developed technique in concurrently recording T_core and T_sq proves efficient and feasible to simultaneously record temperatures of different body sites in free-roaming animals, thereby overcoming potentially erroneous artifacts caused by frequent experimenter intrusion.