A nonsurgical method allowing continuous core temperature monitoring in mares for extended periods, including during endurance exercise

Abstract

Body temperature can be a useful measure of how well the horse responds to thermal challenges of exercise and environment. Currently there is little information available about how body temperature changes throughout an endurance ride, and no nonsurgical methods to evaluate internal temperature of exercising horses during prolonged periods and during long distances. To develop and test a nonsurgical method, using temperature loggers, of continuously recording internal temperature during exercise and over an extended period. Loggers were inserted transcervically into the uterus of mares to measure internal temperature. A total of 9 mares were implanted for periods of 3 days to 6 weeks. The internal temperature was recorded while horses underwent their normal training and competition. Loggers were validated against rectal temperature over a range of internal temperatures while mares were alternatively exercised and rested. The technique proved to be straightforward and accurate. There were no ill effects observed and all mares retained the logger in utero until removal manually, except for one mare, which expelled the logger when she came into oestrus. The intrauterine and deep rectal temperatures were highly correlated and increased during exercise and decreased with aggressive cooling after exercise. The technique is a useful and accurate nonsurgical method for prolonged monitoring of internal temperature in mares, including those animals in athletic competition. This method allows more intensive studies of core temperature during prolonged exercise in competition and under different environmental conditions. It also enables comparison to be made of different methods of cooling of horses post exercise.