Technical note: Development of a transcervical oocyte recovery procedure for sheep

An oocyte recovery procedure was developed and evaluated to determine wheth er a transcervical embryo recovery procedure is feasible with our method, w hich includes estradiol-17 beta (E2) and oxytocin (OT) treatments, for dila ting the cervix in ewes. On d 6 of an estrous cycle, oocytes were recovered either transcervically or with a laparotomy procedure. In the laparotomy g roup, ovulation rate was determined during the procedure and was used to ca lculate the percentage of oocytes recovered. The laparotomy procedure was a standard uterine flush, and 12 mt of PBS was used to flush each uterine ho rn. In the transcervical group, the ovaries in each ewe were evaluated ultr asonically to determine ovulation rate. For transcervical recovery, 100 mu g of E2 were injected i.v. on d 5 to increase cervical OT receptors, and 10 0 USP units of OT were injected i.v. 10 to 12 h later to dilate the cervix. Approximately 25 min after OT, ewes were placed in dorsal recumbency in a Commodore cradle, and a modified Foley catheter was passed through the cerv ix and into the uterus for injection (80 to 210 mt) and aspiration of PBS. The PBS was aspirated with a vacuum pump. The percentage of PBS recovered w as greater (P < .01) at laparotomy than with the transcervical procedure (8 5.8 vs 36.2%). Despite that difference, oocyte recovery did not differ sign ificantly between the two groups (67% for laparotomy vs 50% for transcervic al; [oocytes recovered/number of corpora lutea] x 100), and there was no ev idence that the transcervical procedure damaged the oocytes; the zona pellu cida remained intact around all of the oocytes. In conclusion, a procedure that includes E2-OT-induced cervical dilation, passage of a modified Foley catheter into the uterus, and incremental infusion and aspiration of media through the catheter can be used to recover oocytes transcervically from ew es. This procedure may make transcervical embryo recovery feasible for shee p.