In Vitro Ovine Embryo Production: the Study of Seasonal and Oocyte Recovery Method Effects

Abstract

Background:To current knowledge, different oocyte's recovery method and various seasons have profound impact on in vitro embryo production (IVEP).Objectives:The aim of this study was to define an efficient recovery method for oocytes harvesting from slaughterhouse material in different seasons, and their effects on IVEP yield.Materials and Methods:Ovaries from slaughtered ewes in breeding season (BS) and non-breeding season (NBS) were collected from a local abattoir. The oocytes were recovered through aspiration, centrifugation (ORC), puncture and slicing, and categorized into three classes (I, oocytes with more than three layers of cumulus cells; II, less than three layers with damaged cumulus cells; III, denuded oocytes). After cultivation in TCM 199 for 24 hours, matured oocytes were subjected to in vitro fertilization (IVF) and in vitro culture (IVC). The oocyte recovery using ORC in BS and NBS was significantly higher (P < 0.05) compared with other recovery methods.Results:No significant dissimilarities in the proportion of oocytes reaching M-II stage were recorded when using different oocyte recovery methods in different seasons. Aspiration resulted in lower (P < 0.05) proportion of class I (BS, 60.0 ± 2.1; NBS, 51.1 ± 2.1) compared to ORC (BS, 82.0 ± 1.2; NBS, 70.0 ± 1.2), slicing (BS, 80.0 ± 2.1; NBS, 71.0 ± 1.4) and puncture (BS, 80.0 ± 1.5; NBS, 72.0 ± 2.0). Monospermy and blastocyst development rates were significantly higher using ORC than other recovery techniques in both BS and NBS. More oocytes with high quality, greater blastocyst development and oocyte recovery rates were achieved in BS.Conclusions:The results revealed that oocytes harvesting technique and season are effective in the rate of cleavage and blastocysts’ development, and suggest that despite same meiotic resumption rate in all treatments, it would be better to use ORC.

Antioxidative Potential of Red Deer Embryos Depends on Reproductive Stage of Hind as a Oocyte Donor

“…Thus, the development rate, ranging between 12.28% in pregnant females and 21.82% in non-pregnant hinds on the 4th day of the cycle, is dependent on the reproductive status. The differences in the development rate of blastocysts have been shown previously by Dadashpour Davachi et al, who obtained higher efficiency with the ewes in the breeding season, compared with the females in anestrous phase [40]. Nevertheless, the opposite results in which the blastocyst development rates were independent of the season were presented in sika deer by the laparoscopic ovum pick-up, ranging from 22% to 34% of the total oocytes during the non-breeding and breeding seasons [41].…”

Effect of Reproductive Status on Yield and in Vitro Maturation of Oocytes of Egyptian Sheep

“…As proved in our study, several investigators indicated higher oocyte yield in breeding than in nonbreeding season. In this respect, Dadashpour et al (2014) found that the number of goat oocytes recovered by different collection methods was higher in breeding than in non-breeding season. Also, Majeed et al (2015) reported that recovery rate was higher (87.3%) in breeding season than in non-breeding one (72.5%).…”

“…In this way, Farag et al (2010) recorded higher proportion of COCs and improved oocyte yield/ovary in sheep during spring than in winter and summer. In goats, the highest recovered oocyte yield was found in the breeding season, irrespective of recovery technique (Dadashpour et al, 2014). In sheep, COCs percentage was lower (P<0.05) in winter than in summer (Seydou et al, 1999;Gou et al, 2009).…”

“…However, the incidence of degenerated or very bad oocytes was not influenced by season. Improving recovery of goat oocytes in the breeding season may reflect release of sufficient concentration of gonadotrophins and steroid hormones during the breeding season (Dadashpour et al, 2014). On the other hand, Cognie et al (1999) reported insignificant effect of breeding season on yield of recovered oocytes in sheep and goats.…”

“…Improving oocyte yield in breeding season may attributed to the presence of more follicles during the breeding season. Generally, the highest number of recovered oocytes might reflect the optimum level of gonadotropins and steroids in breeding season (Dadashpour et al, 2014). In sheep, some authors have suggested that seasonal anoestrous in non-breeding season can adversely affect the number of recovered oocytes per female (Stenbak et al, 2001;Vázquez et al, 2009).…”