Background: Rhythmicity in core body temperature has been extensively studied in humans and
laboratory animals but much less in farm animals. Extending the study of rhythmicity of body
temperature to farm animals is important not only from a comparative perspective but also from
an economic perspective, as greater knowledge of this process can lead to improvements in
livestock production practices. In this study in cattle, we investigated the maturation of the daily
rhythm of body temperature in newborn calves, characterized the parameters of the daily rhythm
in young cows, and studied the oscillation in body temperature associated with the estrous cycle
in adult cows.
Results: We found that the daily rhythm of body temperature is absent at birth but matures fully
during the first two months of life. The mature rhythm had a mean level of 38.3°C, a range of
excursion of 1.4°C, and was more robust than that of any mammalian species previously studied
(90% of maximal robustness). Sexually mature cows also exhibited a robust estrous rhythm of body
temperature. An elevation of about 1.3°C was observed every 21 days on the day of estrus. Small
seasonal variations in this pattern were observed.
Conclusion: In conclusion, calves exhibit a very robust daily rhythm of body temperature,
although this rhythm is absent at birth and develops during the first two months of life. Adult cows
exhibit also 21-day rhythmicity in body temperature reflecting the duration of the estrous cycle.