Hoof cortisol variation in calves during the neonatal period.

The neonatal period is a critical phase of the animal’s life cycle. The hoof in the neonatal period undergoes significant changes. The claw incorporates endogenous hormones that passively diffuse from capillaries to the hoof matrix during keratinisation over a longer time period. The aim of this study was to characterize hoof cortisol concentrations in 20 calves at 30 and 60 days of age. The samples were obtained from the front right hooves during claw trimming. The clipped sole samples obtained had the thickness of 0.5–0.7 mm and, according to the rate of hoof growth, represent the endocrine milieu for approximately 1 month before trimming. Cortisol concentrations of freeze-dried clipped claw samples were evaluated by RIA after extraction with methanol. Hoof cortisol levels in calves decreased (p < 0.05) from the first to the second month of life. Because hoof cortisol detected at 30 days of age represents the cumulative effect of parturition and neonatal adaptation, the significant decrease trend suggests the progressive ability of calves to cope with the environment through the allostasis, a process promoted by body systems including the hypothalamic-pituitary-adrenal axis. This preliminary study showed that hoof can be used to measure cortisol, a hormone that could have an influence on the bovine claw’s physiology.