This study evaluated the effect of two mating methods (GNM: natural mating or GAI: laparoscopic artificial insemination) on superovulatory response, fertility and embryo yield in superovulated ewes. Fifteen non-pregnant Santa Inês ewes were superovulated and either mated by GNM or GAI in a crossover design. Oestrus was synchronised using intravaginal progestagen sponges for 6 days and on Day 5, 300 IU eCG and 0.0375 mg d-cloprostenol were given. Twelve hours after sponge removal, 0.025 mg gonadotropin-releasing hormone was administered. Superovulation started 48 h after gonadotropin-releasing hormone treatment, using 5 IU/kg follicle-stimulating hormone (pFSH). At the first pFSH dose, new sponges were inserted. At the fifth dose, 0.0375 mg cloprostenol was administered and the sponges were removed. The GNM was mated with rams every 12 h, until the end of oestrus. The ewes of GAI were laparoscopic inseminated with frozen–thawed semen 36 and 48 h after sponge removal. Ultrasonography was performed every 24 h from the beginning of oestrus synchronisation treatment and every 12 h from the second sponge removal to 2 days after the last pFSH dose. Six to seven days after mating, the number of corpora lutea (CL) was evaluated by laparoscopy and the females with > 4 CL were subjected to embryo collection. The interval from sponge removal to ovulation was shorter (P < 0.05) in the GNM. The overall superovulatory response was 63.3% (19/30), with 60.0% and 66.7% in GNM and GAI, respectively (P > 0.05). The number of recovered structures (6.4 ± 2.4 vs 4.5 ± 3.0), recovery rate (74.0 ± 16.0 vs 52.3 ± 26.5%), number of transferable embryos (3.0 ± 2.9 vs 3.6 ± 2.0) and viability rate (47.2 ± 45.3 vs 77.4 ± 37.1%) did not differ between GAI and GNM (P > 0.05). However, the GAI group showed a higher (P < 0.05) number of unfertilised oocytes (3.1 ± 3.1) and a higher non-fertilisation rate (47.1 ± 45.3%) than the GNM (0.9 ± 2.1 and 11.5 ± 21.5%). The mating method did not affect the superovulatory response, and production of viable embryos although the non-fertilisation rate has been inferior for the AI group.

There is still no consensus regarding the best protocol for in vivo embryo production in sheep despite increasing studies in this area. Moreover, there is variability in the response of ewes to superovulation (SOV). An approach to mitigate this inconsistency is to initiate gonadotropin administration under favorable ovarian conditions. The present study compared three treatments in a crossover design: a traditional SOV protocol (TRAD) and “Day 0” D0 SOV protocol with (D0+GnRH), or without Lecilerin (D0-GnRH). Fifteen Santa Inês ewes received 200 mg of FSH at six decreasing doses and PGF2α with the fifth dose of FSH. They were naturally mated with fertile rams and subjected to surgical embryo collection. The number of viable embryos was similar among the different treatments (TRAD = 6.0 ± 4.7; D0-GnRH = 3.8 ± 6.4; D0+GnRH = 7.5 ± 6.5). Regardless of the treatment method, ewes with follicles ≤ 4 mm, at the first FSH dose, produced more viable embryos (9.6 ± 6.0, P < 0.05) compared to ewes that had follicles > 4 mm at the beginning of the SOV (2.9 ± 3.1, viable embryos). Both the TRAD and D0+GnRH groups had fewer animals with large follicles (> 4 mm) at the first FSH dose than the D0-GnRH group (P < 0.05). In conclusion, both the TRAD and D0+GnRH treatments induced a more favorable ovarian condition (follicles ≤ 4 mm) for adequate SOV; although, all three treatments exhibited similar efficacies in Santa Inês sheep.

The aim of this study was to determine the intervals between sponge removal and the onset of estrus, sponge removal and the first detected ovulation, and onset of estrus and the first ovulation, and also to determine the duration of estrus, in superovulated Santa Inês ewes subjected to natural mating (NM) and AI. The trial was done in July and February at Cachoeiras de Macacu–Rio de Janeiro (22°27′S, 43°39′W). Fifteen non-pregnant Santa Inês ewes, age 3.4 ± 1.4 years, weighing 47.8 ± 6.3 kg, with 3.3 ± 0.4 body condition score (scale of 1 to 5), were randomly assigned to 2 groups. Both groups were superovulated using the same protocol and were mated in a crossover design by NM and laparoscopic AI. Estrus was synchronized using intravaginal sponges (60 mg of medroxyprogesterone acetate; Progespon®, Schering Plough Animal Health, São Paulo, Brazil) inserted (Day 0) and maintained for 6 days. On Day 5, the ewes received IM injections of 300 IU of eCG (Novormon®, Schering Plough Animal Health) and 0.0375 mg of cloprostenol (Prolise®, Tecnopec, São Paulo, Brazil). Twelve hours after sponge removal, 0.025 mg of gonadorelin acetate (Gestran®, Tecnopec) was administered IM. Superovulation started 60 h after sponge removal and consisted of 5 IU kg–1 of porcine FSH (pFSH; Pluset®, Hertape Calier, Minas Gerais, Brazil) IM in 6 decreasing doses (25, 25, 15, 15, 10, and 10%) at 12-h intervals. At the first pFSH dose, new sponges were inserted. At the fifth pFSH dose, 0.0375 mg of cloprostenol was administered IM and the sponges were removed. After the sponge removal, the NM group was exposed to rams twice per day for mating, until the end of estrus. In the AI group, estrus was detected using a teaser with the penis diverted. The females were permitted to be mounted twice per day until the end of estrus, and were inseminated with frozen–thawed semen 24 and 36 h after the end of superovulation. The follicular development and ovulation time were observed using real-time ultrasonography (8.0 MHz Pie Medical®, Aquila Vet, Tokyo, Japan) at 12-h intervals. For statistical analysis, a Student’s t-test was performed (5% significance level) using the BioEstat program. Results are presented as mean ± standard deviation. The time from sponge removal to onset of estrus and the duration of estrus did not differ between NM and AI groups (31.79 ± 5.94 v. 25.25 ± 10.38 h and 29.89 ± 11.54 v. 26.66 ± 8.67 h, respectively). The time from sponge removal to ovulation and from onset of estrus to the first ovulation were shorter (P < 0.001) in the NM group (32.11 ± 12.72 v. 56.48 ± 15.39 h and 8.61 ± 5.99 v. 32.25 ± 18.57 h, respectively). The time from sponge removal to ovulation in July and February was 56.07 ± 7.27 versus 56.83 ± 20.72 in the AI group and 29.54 ± 0.56 versus 33.83 ± 19.02 in the NM group, respectively, suggesting that the season of the year in a tropical region did not influence the ovulation time for each treatment. Possibly, the mechanical stimulation induced by the contact of the penis with the vagina fornix and by the accessory sex glands fluids in mating hastened the ovulation time in the NM group. The service can shorten the time of ovulation.