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

Abstract

Contents Multiple ovulation and embryo transfer (MOET) is an important tool in the sheep industry for increasing numbers of genetically superior individuals. The objective of this study was to evaluate the effect of semen source (frozen or fresh), the number of embryo collection procedures for each donor (NECP), the season in which embryo transfer and collection was performed, and the age and breed of the donor, on the number of recovered embryos and pregnancy rates after embryo transfer. The Alamos Genetics’ flushing station database was used. This consisted of 140 embryo collection procedures, from 53 Dorper and White Dorper sheep donors, aged between one and eight years, totalling 1,200 collected embryos. Neither the number of retrieved embryos nor the pregnancy rate was affected by the semen preservation method (fresh or frozen), NECP or the age and breed of donor. The season did not affect the number of collected embryos but had a significant effect (p < 0.05) on the recipient pregnancy rate, with higher pregnancy rates reported in the winter (65.57% ± 25.33%) compared with spring (37.11% ± 33.27%), summer (29.95% ± 28.33%) or autumn (35.03% ± 31.66%). There is an estimated increase of 98.4% and 71.5% of embryos recovered in the spring and summer seasons, respectively, when winter is used as reference. The survival of embryos is significantly higher when implanted during the breeding season, more specifically in winter. Embryo collection can be carried out throughout the year in sheep, but there may be a marginal advantage in the use of superovulation and fresh embryo transfer programmes in the autumn and winter.

Effects of recipient oocyte source, number of transferred embryos and season on somatic cell nuclear transfer efficiency in sheep

“…This trend follows the natural seasonal regulation of oestrous cycling. Our results are consistent with a recent report describing Dorper sheep embryo transfer (Bergstein‐Galan, Weiss, & Kozicki, ). In that study, the season had a significant effect on the recipient pregnancy rate, with higher pregnancy rates reported in winter (65.57% ± 25.33%) than in spring (37.11% ± 33.27%), summer (29.95% ± 28.33%) or autumn (35.03% ± 31.66%).…”

“…Ovine oestrous cycles generally start and end when the day length is decreasing and increasing, respectively. Our results showed that season had a significant effect on pregnancy and live lamb rates, which were significantly higher when embryos were transferred in November-December (winter) than in & Kozicki, 2019). In that study, the season had a significant effect on the recipient pregnancy rate, with higher pregnancy rates reported in winter (65.57% ± 25.33%) than in spring (37.11% ± 33.27%), summer (29.95% ± 28.33%) or autumn (35.03% ± 31.66%).…”

Multiple ovulation and embryo transfer in sheep: Effects of embryo developmental stage and quality on viability in vivo under farm conditions

“…[1][2][3][4] For these technologies to be efficiently implemented, the number of progeny born from genetically superior females must be maximised. 5,6 Whilst affected by numerous factors, the number of lambs born per donor female are directly related to the viability of transferred embryos. 5 Embryo viability in various species has been found to be affected by embryo developmental stage and quality at the time of transfer, the number of embryos transferred and the type of semen (fresh or frozen-thawed) used for artificial insemination (AI).…”

Correlation analysis of serum reproductive hormones and metabolites during multiple ovulation in sheep

“…The embryo collection protocol was followed as Bergstein-Galan et al [ 14 ]. Brifely, donors were sedated with acepromazine 1% (0.05 mg/kg, IM) and inhalation anaesthesia induced with isoflurane.…”