418 EFFECT OF SUPEROVULATION INITIATED AT FOLLICULAR WAVE EMERGENCE IN SANTA INÊS EWES

Abstract

Superovulation in ewes has been a source of many studies aimed at obtaining high superovulatory response and number of viable embryos recovered. In a protocol called Day 0, superovulatory treatment was initiated at the time of wave emergence in the absence of a dominant follicle (Menchaca A et al. 2002 Theriogenology 58, 1713-1721). The aim of this study was to compare ovarian response and number of embryos recovered after treatment between ewes treated with a Day 0 protocol and those treated with a traditional protocol. Santa InÊs ewes (n= 18) between 2 and 5 years old were randomly distributed into 2 superovulation treatment groups: traditional protocol and Day 0 protocol. Each treatment was repeated twice in a crossover model. The traditional protocol consisted of the intravaginal insertion of a sponge containing 60 mg of medroxiprogesterone acetate (MAP; Progespon^®, Tecnopec, São Paulo, Brazil) for 14 days, which was replaced on Day 7, followed by 150 μg of cloprostenol (Prolise^®, Tecnopec) i.m. On Day 12, FSH (Folltropin^®-V, Bioniche, Belleville, Ontario, Canada) treatment was initiated using a total dose of 200 mg, given in twice-daily i.m. injections that decreased in dose over 4 days. A dose of 200 IU of eCG (Novormon^®, Syntex, Buenos Aires, Argentina) i.m. was given at the time of sponge withdrawal. The AI was done by laparoscopy at 48 and 55 h after sponge withdrawal using fresh semen. The Day 0 protocol consisted of a previous 9-day synchronization treatment with a sponge containing 60 mg of MAP, followed by 150 μ of cloprostenol i.m. and 200 IU of eCG i.m. given on Day 7. A dose of 0.05 mg of GnRH (lecirelin; Gestran Plus^®, Tecnopec) i.m. was given 16 h after sponge withdrawal. In a preliminary study, 38 ewes ovulated 42 ± 52 h after sponge withdrawal. Therefore, 48 h after sponge removal was considered as Day 0 and FSH treatment was initiated at that time, with a total dose of 200 mg of Folltropin^®-V, given in 6 twice-daily decreasing doses. Two doses of cloprostenol (150 μg) were given i.m. concurrent with the fifth and sixth FSH treatments. Gonadotropin-releasing hormone (0.05 mg of lecirelin i.m.) was given 12 h after the last FSH treatment. Artificial insemination with fresh semen was done by laparoscopy 16 and 26 h after GnRH treatment. Five days after AI, embryos were recovered surgically. Results were evaluated by the parametric t-test. The number of corpora lutea and ova/embryos recovered did not differ (P > 0.05) between the traditional (9.8 ± 5.3; 4.5 ± 4.6) and Day 0 (10.0 ± 6.0; 3.5 ± 4.3) protocols. Similarly, no difference in the number of viable embryos was observed between treatments (1.6 ± 2.0 and 1.7 ± 2.4 for the traditional and Day 0 treatments, respectively). Within viable embryos, the traditional protocol (0.4 ± 1.0) resulted in ahigher (P < 0.05) number of morulae than that of the Day 0 protocol (0.1 ± 0.3). The ewes that had no superovulatory response did not differ (P > 0.05) between the traditional (11.11%) and Day 0 (5.56%) protocols. In summary, there was no difference in the parameters evaluated between both protocols.

Financial support: FAPDF, CNPq, Tecnopec.