Annual rhythmicity and maturation of physiological parameters in goats.

This study was conducted to investigate seasonal rhythmicity and maturation of physiological parameters in goats. Five kids (Capra hircus, Maltese breed) were studied for 24 months, starting at 5 months of age. Rectal temperature and various blood-borne substances (melatonin, cholesterol, urea, total bilirubin, albumin, glucose, calcium, magnesium, phosphate, and sodium) were measured once a month at dawn and dusk. Serum bilirubin concentration exhibited statistically significant 12-month rhythmicity, and melatonin concentration exhibited 6-month rhythmicity. Changes in the dusk-to-dawn difference in rectal temperature during the course of the study provided suggestive evidence that the circadian rhythm of body temperature in goats is not fully developed until the end of the second year of life. The results documented also maturational changes in cholesterol production and blood glucose regulation.