engleski

The effect of the origin of the immature oocytes on in vitro developmental competence of bovine embryos

Numerous researches suggest that the intrinsic quality of the oocyte is the critical factor determining the proportion of the oocytes developing to the blastocyst stage, although culture conditions also affect developmental potential of the embryo. The aim of this research was to compare the embryo developmental competence of immature oocytes recovered from slaughterhouse ovaries (SO) and those recovered in vivo by ovum pick up (OPU). Transvaginal ultrasoung guided (Pie Medical, Netherlands) oocyte collection was performed in 6 Simmental donor heifers. Heifers were synchronized with PGF2 and stimulated with pFSH, twice a day during two days (Folltropin® ; ; -V, Vetrepharm Inc., London, Canada, a total dose: 200 mg NIH-FSH-P1). OPU was performed 48 hours after the last FSH injection and procedure was repeated once a week for six consecutive weeks. Oocytes were matured, fertilized and cultured in vitro in SOFaaBSA until Day 9. The cleavage rates on Day 2, the total number of morulas (M) and blastocysts (Bl) on Day 7 and the numbers of hatched blastocysts (hBl) on Day 9 were recorded. Differential staining of the inner cell mass (ICM) and trophectoderm cells were performed on random samples on Day 7 blastocysts (n=24). The results were analyzed with ANOVA (StatSoft, Statistic, version 7.1.) and with Tukey’ s tests post-hoc analysis. The results are presented in the table. Table: Effect of bovine oocyte origin on in vitro development of embryos (mean± ; ; SD) Oocyte origin N Cleavage (%) M/Bl (%) HBL (%) Slaughterhouse oocytes 398 76.83 (± ; ; 2.31)a 29.96 (± ; ; 2.08) a 16.78 (± ; ; 0.78) a OPU-derived oocytes 212 81.29 (± ; ; 8.83) a 44.71 (± ; ; 7.20)b 35.57 (± ; ; 5.87) b Values with different superscripts within the same columns differ significantly (P<0.05 ; ANOVA) The proportion of ICM cells in day 7 blastocysts was significantly higher in OPU derived embryos (29.36± ; ; 1.16% vs. 26.05± ; ; 0.8%, p<0.05). These results demonstrate that the immature oocytes recovered in vivo after OPU are more competent to develop to the blastocyst stage than those derived from slaughterhouse ovaries. Also, the oocyte origin seems to have an effect on the quality of the blastocyst in terms of the proportion of ICM cell number.

cow ; oocyte ; developmental competence ; ovum pick up

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