Persistent homeothermy in large domestic mammals maintained under standard farming conditions

Background Mammals, particularly large domestic ones, are considered to be year-round homeotherms. Surprisingly, however, very few long-term studies of the stability of core temperature of large domestic mammals have been conducted. Methods We monitored the auricular temperature and rectal temperature of goats, sheep, cows, and donkeys monthly for 2 years and compared their annual variation with their daily and day-to-day variations. Results Although ambient temperature varied from 8 °C in the winter to 30 °C in the summer, auricular temperature varied less than 0.5 °C, and rectal temperature varied less than 0.3 °C. We found that the daily oscillation in body temperature was up to three times as large as the day-to-day and month-to-month variations and that month-to-month variation was negligibly larger than day-to-day variation. Conclusion Our results confirm persistent homeothermy in large domestic mammals with unrestricted access to food and water and provide a quantitative measure of the relationship between long-term homeothermy and the wider range of daily/circadian oscillation.