Rectal temperature, breathing and heart rates were recorded in kids and lambs starting an hour after birth. Kids and lambs were divided into 2 groups, singleton (5 kids and 5 lambs) and twin (8 kids and 8 lambs), born at term in spring at the same hour (08:00 ± 1 hour) and clinically healthy. They were housed in a common stall and were fed only with colostrum and maternal milk. Each profile was analyzed individually by the Cosinor method. No rhythmicity as a group could be identifying. Our data showed that the maturation of the circadian system is almost complete in newborn, but there is subject variability in its manifestation in the early hours after birth.