Hypothalamic Temperature Regulation in Cattle

IT was theorized that routine access to the hypothalamus by means of indwelling cannulae would allow rapid testing of efficiency in control of body temperature of cattle. A semi-stereotaxic method for cannulae instal-lation was developed. The heat loss center of two female beef calves was heated by RF energy; some degree of correlation was observed between hypo-thalamic temperature and respiration rate. Animals were subjected to a step change in thermal environment (75 to 95 F with very high humidity); rectal and hypothalamic temperatures were found to be coupled by the respiration rate, with marked individual differences. The approach appears to have merit as a system for rapid identification of heat tolerant breeds and individuals.