SEASONAL VARIATION IN OVULATORY ACTIVITY OF NUBIAN, ALPINE AND NUBIAN × CRIOLLO DOES UNDER TROPICAL PHOTOPERIOD (22° N) (VARIACIÓN ESTACIONAL DE LA ACTIVIDAD OVULATORIA DE CABRAS NUBIA, ALPINA Y NUBIA × CRIOLLA EN CONDICIONES DE FOTOPERIODO TROPICAL (22° N))

SUMMARY In the present study, seasonal variation in ovulatory activity of Nubian, Alpine and Criollo × Nubian goats in the semiarid region of central-northern Mexico (22° 14’ N) was examined. The study was conducted under natural photoperiod and climate conditions during a whole year. Eight female goats per breed were grouped separately and exposed to visual, olfactory and audible signals of bucks. Blood samples were obtained twice per week and serum progesterone concentrations were determined. All goats presented a clear pattern of seasonal ovulatory activity based on serum progesterone profiles. Length of the ovulatory activity period did not differ between genotypes (P >0.10), and had an average duration of 4.3 months. Nevertheless Criollo × Nubian goats presented greater individual variation in dates of onset and end as well as length of this period (P <0.05). Results indicate that female goats of genotypes which differ in latitude of origin, express a similar restricted pattern of seasonal ovulatory activity when subjected to small annual changes in phtoperiod, adequate nutrition and incomplete socio-sexual stimulus,