Effects of Season and Superovulatory Treatment on Embryo Yields in Fine‐Wool Merinos Maintained Under Field Conditions

Abstract

The aim of the study was to assess the effects of superovulatory treatment (multiple FSH-dose vs single-shot FSH treatment) and seasonality on embryo yields in fine-wool Merino ewes. Treatment based on multiple FSH-dose consisted of 200 mg of FSH (Folltropin(®)) administered in seven decreasing doses. Single-shot treatment consisted of a single dose of 70 mg of FSH + eCG. In ewes treated with multiple FSH doses, number of recovered embryos was higher (6.0 ± 0.5 vs 3.5 ± 1.0), while non-fertilization rate was lower (12.8 ± 3.9 vs 40.3 ± 9.5) during the breeding season when compared to the non-breeding season (p < 0.05); although similar values of recovered Grades 1-2 embryos were observed between seasons. During the breeding season, proportion of responding ewes (98.1 vs 57.1%), ovulation rate (13.9 ± 0.8 vs 3.2 ± 1.2), recovered structures (7.9 ± 0.6 vs 1.7 ± 0.7), total recovered embryos (6.0 ± 0.5 vs 1.2 ± 0.6) and good-quality embryos (5.1 ± 0.5 vs 0.9 ± 0.6) were higher for the multiple FSH-dose treatment than for the single-shot protocol. In a similar way, in the non-breeding season, ovulation rate (11.3 ± 1.8 vs 6.0 ± 1.1) and recovered structures (6.6 ± 1.2 vs 2.7 ± 0.6) were higher for the multiple FSH injections protocol than those for the single-shot treatment, resulting in higher recovered Grades 1-2 embryos (3.2 ± 0.9 vs 1.4 ± 0.5). Current results indicate that seasonal anestrus affected embryo yields when applying multiple FSH-dose superovulatory treatment in Merino ewes, by decreasing the number of recovered embryos although the number of recovered good-quality embryos was not affected. During both seasons, multiple FSH injections produced higher ovarian response and number of viable embryos than the single-shot treatment.

Preliminary results evaluating a simplified superovulation protocol in Boer goats

“…Similar results have been reported in sheep (Cueto et al, 2011). However in goats the ovulation and oocyte recovery rate were reported to be similar between the multiple FSH protocol and the simplified protocol (Baldassarre et al, 2002 andFreitas andMelo, 2010).…”

“…Not only was the oocyte recovery rate improved, but also a higher number of good quality embryos (Gibbons et al, 2007 andSimonetti et al, 2008). To the contrary, Cueto et al (2011) reported that one shot protocol reduced the number of corpora lutea (CL's) and embryo recovery rate regardless of the season in sheep. In goats where a multiple regime and one shot FSH and eCG protocols were compared, a similar superovulation response was reported, based on the number of follicles visualised and aspirated, as well as the number of oocytes collected (Baldassarre et al, 2002 andFreitas andMelo, 2010).…”

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

“…According to Armstrong and Evans (), the fertility rate is markedly reduced when superovulated sheep were inseminated with frozen semen, however, fertility rate is partly restored after laparoscopic insemination. High rates of unfertilized oocytes, ranging from 12.8% ± 3.9% to 40.3% ± 9.5%, were reported by Cueto, Gibbons, Pereyra‐Bonnet, Silvestre, and González‐Bulnes () after performing LAI with 100 million thawed spermatozoa in superovulated merino sheep. Poor fertilization may, partly, be due to poor synchrony between time of insemination and ovulation (Baldassarre & Karatzas, ) as well as to low inseminating dose.…”

Effect of single-chain ovine gonadotropins with dual activity on ovarian function in sheep

“…This may also explain the fact that Lemke et al observed: a more pronounced E 2 production in ewes treated with dually active chimeric gonadotropins and increased numbers of CL and ovarian weight. The administration of highly purified porcine pituitary extract to ewes in the breeding season significantly increases the number of recovered embryos than that during the nonbreeding season (Cueto et al 2011). In addition, the effect of season on the ovulatory response of ewes treated with pregnant mare serum is lowest in the spring and highest in the fall (Gherardi & Lindsay 1980).…”