SEASONAL VARIATION IN OVULATORY ACTIVITY OF NUBIAN, ALPINE AND NUBIAN X CREOLE DOES UNDER TROPICAL PHOTOPERIOD (22° N)

In the present study, seasonal variation in ovulatory activity of Nubian, Alpine and Criollox 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 x Nubian goats presented greater individual variation in dates of onset and end as well as length of this period (P