Maturation of the daily body temperature rhythm in sheep and horse

Abstract

The ontogeny of circadian rhythmicity in farm animals has received very little attention in the chronobiological literature. In this study, the maturation of the daily rhythm of body temperature during the first month of life was investigated in lambs and foals. In both lambs and foals, the adult daily pattern of body temperature oscillation (i.e., consistently higher temperatures at dusk than at dawn) was detectable within the first 10 days of life and was fully attained a month after birth. In the lambs, more clearly so than in the foals, the difference in temperature between dawn and dusk was achieved almost exclusively by a gradual elevation of temperature at dusk, while the temperature at dawn remained unaltered. In adult sheep, rectal temperature had a daily range of 1.0°C with a mean of 39.1°C. In adult horses, the range was 0.5°C and the mean was 38.1°C.