353 FOLLICULAR POPULATION STATUS AT THE FIRST FOLLICLE-STIMULATING HORMONE INJECTION IN EWES SUPERSTIMULATED NEAR THE FIRST FOLLICULAR WAVE OF CIDR PROTOCOL

Abstract

This study was designed to evaluate the follicular status at the 1st FSH injection in ewes superstimulated near the 1st follicular wave of the CIDR protocol during nonbreeding (NB), transition (T), and breeding (B) season, and thus to correlate them with the superovulatory response (SR). On Day 0, all females (30 Santa Ines ewes; n = 10 per season) received a progesterone (P4) device (CIDR®; Zoetis, Brazil) and 37.5 µg of d-cloprostenol. The superestimulation (ST) was initiated on Day 4, 4, and 6 of protocol in the NB, T, and B season, respectively. These follicular wave emergence days were defined in a previous study that evaluated the follicular dynamic in P4 protocol (Oliveira et al. 2011 Acta Scientiae Veterinariae, 38, 361). The ST consisted of 8 injections of pFSH administrated twice a day in descending order (40/30/20/ and 10 mg of pFSH; Folltropin-V, Bioniche, Canada). The P4 device was removed 2 days after the beginning of the FSH treatment and all ewes received another injection of 37.5 µg of d-cloprostenol and a dose of 200 IU of eCG at the same time. B-mode ultrasound of ovaries was performed immediately before the 1st FSH injection. The follicles were classified according to their diameters into categories based on physiological dynamics: (C1) 2–4.25 mm, representative of the population before dominance phase; (C2) 4.5–5 mm, initial dominance phase; (C3) 5.25–5.75 mm, middle dominance phase; and (C4) 6 mm, preovulatory phase. Data were analysed by GLIMMIX using SAS comparing mean values (± s.e.m.) between seasons (P < 0.05) and Pearson correlation was made. All ewes had small follicles (C1) at the beginning the ST; however, only one female had solely C1 follicles. The number of C1 follicles did not differ between seasons (12.9 ± 0.9, 12.8 ± 0.8, and 12.1 ± 0.5 follicles for the NB, T, and B season, respectively). One-half of the animals from NB and T seasons had no C3 and C4 follicles, whereas 40% of females in B season showed the same follicular status. The percentage of ewes that had no C4 follicles was 80, 100, and 50% for the NB, T, and B season, respectively. There were no difference between season in number of C2 follicles (1.8 ± 0.5, 1.7 ± 0.4, and 1.7 ± 0.4) and C3 follicles (0.3 ± 0.1, 0.6 ± 0.2, 0.1 ± 0.1) for NB, T, and B seasons, respectively. However, the number of C4 follicles was significantly higher (P < 0.05) in the NB (0.2 ± 0.13) and B (0.6 ± 0.2) season than T period, which had no follicles in this category. The SR did not differ between seasons (12.4 ± 0.9, 13.1 ± 2.3, and 17.0 ± 2.3 for the NB, T, and B season, respectively) and had no correlation to any follicular category. In conclusion, the ST started on a day when there was a large population of small follicles, regardless of the season, confirming proximity to follicular wave emergence. However, the ovarian population was not restricted to this category. Therefore, it is possible that wave emergence has already started in some ewes before the initiation of the ST.

Financial support is from FAPESP and CNPq.