Effect of natural mating or laparoscopic artificial insemination in superovulated Santa Inês ewes on superovulatory response, fertility and embryo viability

Abstract

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.

Effect of semen and donor factors on multiple ovulation and embryo transfer (MOET) in sheep

“…These two situations can be solved when LAI is performed twice with the interval of 6 hr, which coincides with the median time from first to last ovulation reported in superovulated sheep(Cognié, Baril, Poulin, & Mermillod, ). The use of two LAI produces good results in multiple ovulated sheep fertilized with either fresh and frozen semen (respecting inclusion criteria), similar results were reported by Lima et al () and Buffoni et al ().…”

Three superovulation protocols for in vivo embryo production in Santa Inês sheep

“…These authors reported a higher mean of transferable embryos (7.9) in Merino sheep after day 0 treatment when compared to the animals that underwent a traditional (14 days of progestogen) SOV protocol (this last group producing a mean of 5.9 transferable embryos). However, the same methodology could not reach similar embryo outputs in Santa Inês sheep (LIMA et al, 2015;SOUZA-FABJAN et al, 2017;SANTOS et al, 2020).…”

Towards Improving the Outcomes of Multiple Ovulation and Embryo Transfer in Sheep, with Particular Focus on Donor Superovulation

“…After superovulation, the donor animal can be subjected to either natural mating or AI [ 133 ]. Regardless of the type of superovulation treatment, fertilization usually fails in ewes bred naturally or artificially due to the tightly folded multiple rings of the cervix.…”

“…Regardless of the type of superovulation treatment, fertilization usually fails in ewes bred naturally or artificially due to the tightly folded multiple rings of the cervix. The problem of this inefficient fertilization process can be minimized by the direct intrauterine deposition of semen following exposure by surgical or laparoscopic insemination [ 10 , 133 ]. Increased fertilization (91.5% vs. 44.8%; p < 0.05) with laparoscopic AI than natural mating has been reported [ 63 ].…”

“…Additionally, a lower fertilization rate for superovulated ewes mated naturally than with laparoscopic insemination (75% vs. 82%; p < 0.05) [ 134 ]. However, a higher non-fertilization rate (47.1% vs. 11.5%; p < 0.05) for ewes inseminated through laparoscopic AI than natural mating [ 133 ].This phenomenon of lower fertilization rate during natural and laparoscopic AI may be due to failure in the transport of sperm through the tightly folded cervix, uterus or a sperm quality, or association of lower frozen–thawed semen viability, with asynchrony between ovulation time and insemination time of the commercially available semen [ 135 ].…”