REPRODUCTIVE SEASONALITY IN SUPEROVULATED TROPICAL SHEEP Juárez-Pérez,

Abstract

Objective: Evaluate the effect of reproductive seasonality on superovulated tropical sheep.
Desing/methodology/approach: Twenty Pelibuey sheep were used, 10 in spring and 10 in autumn, with weight and average body condition of 42.5±1.2 kg and 3+, respectively; synchronized to estrus (13 days) by vaginal sponges with 20 mg of fluorogestone acetate (FGA) and a dose of 10 mg mL^-1 of prostaglandin F2a (PGF2a) on day 6. Superovulation was induced with 220 IU 10 mL^-1 of porcine follicle stimulating hormone (FSHp) intramuscular (IM) in eight decreasing doses (2, 2, 1.5, 1.5, 1, 1, 0.5, 0.5 mL) at intervals of 12 hours from day ten. The sponges were withdrawal on day 13 and 30 h after the withdrawal, an IM dose of 100 ug of gonadotropin-releasing hormone (GnRH) was administired. The ovarian response (follicles and corpora lutea) developed during the seven days of sponge withdrawal by endoscopy. The results were analyzed by test X².
Results: The difference between the number of present and ovulated follicles was considered to be atresia follicles, apparently in tropical sheep a major atresia follicular (P<0.05) appears in spring with regard to the autumn (74 vs. 5).
Study limitations/implications: In superovulated tropical ewes, reproductive seasonality is not observed.
Findings/conclusions: A seasonal effect with higher follicular atresia is observed in spring (53.23 %) compared to autumn
(5.43 %).