Circannual fluctuations in serum cortisol and glucose concentrations and hair coat growth in goats

This study characterized serum cortisol (CORT) and glucose (GLUC) levels and the hair cover length in six goat genotypes, Granadina (G), Nubian (N), Saanen (S), Toggenburg (T), Alpine (A), Crosses (C; Saanen x Criollo) throughout the four seasons of the year. Goats (five per breed, 37±3 mo, 42.1±3 kg) were kept under stall-fed conditions. The heaviest BW was displayed by S and T while the best BC (P<0.001) was observed in C, N and G. The S, T and C displayed the largest (P<0.001) values for rump (HR) and neck (HN) hair cover. However, neither CORT nor GLUC differed (P>0.05) among genotypes. The belly hair cover (HB) and HN were the maximum during winter (Wn) and spring (Sp). During fall (Fl) there was the lowest (P<0.001) BC and the most reduced (P<0.001) GLUC. These findings suggest that goats may perceive to both fall environmental conditions and rainfall as potential stressors able to activate the hypothalamic-hypophyseal-adrenal axis, and in turn, may dictate catabolic actions in a cortisol-dependent fashion.