Rectal temperature in Capra hircus, involvement of the daily rhythm of thyroid hormones, uncoupling protein 1 and clock gene Per2

Thermal homeostasis is one of the principal indexes of animal welfare; the circadian rhythm of body temperature is well established and its disruption or alteration are signals of stress. The present study investigated the daily rhythm of 3,5,3'-triiodothyronine (T3), thyroxine (T4), uncoupling protein 1 (UCP1), and clock gene Per2 in Capra hircus to improve the knowledge in this field. Camosciata delle Alpi goats (7 female, 2 years old, 67 +/- 2 kg, clinically healthy), were housed in a stable under natural environmental conditions. Blood sample collections were performed every 4 h for a 48-h period. Serum concentrations of T3, T4, UCP1, and clock gene Per2 were determined. Before the blood sample collection rectal temperature was recorded at all data points. Two-way for repeated measure analysis of variance showed a statistically significant effect of time of day on all studied parameters. T3, T4, Per2, and rectal temperature showed a robust daily rhythm. The acrophases observed in the investigated parameters were statistically different. In particular, T3 acrophase was observed between 20:15 and 21:45; T4 acrophase was between 02:41 and 03:35; Per 2 acrophase was between 7:18 and 08:11; RT acrophase was between 17:45 and 19:55. Per2 expression was correlated with T3 and T4 serum levels, and the rectal temperature values were correlated with T3 and T4 serum levels and Per2 In conclusion, in goats housed in boxes, the rectal temperature daily rhythm was linked to the daily rhythm of thyroid hormones and Per2 clock gene expression in the peripheral blood. In goats not subjected to thermal stress UCP1 did not show a daily fluctuation.