Refinement of transvaginal ovum pick-up in sows increases oocyte recovery and supports in vitro embryo production

BACKGROUND: Efficient recovery of oocytes from sows may facilitate embryo production and increase the number of offspring obtained from breeding sows with desired traits. However, robust protocols for consistent oocyte retrieval in sows are still lacking. The aim of this field study was to evaluate modifications of a transvaginal OPU protocol in multiparous sows, including the use of anaesthetics and analgesics, different aspiration flow rates, and hormonal treatments. Furthermore, the effect of partial in vivo oocyte maturation prior to in vitro embryo production (IVEP) was assessed. Thirty-two hybrid sows (parity 5-7) were included in three experiments. In Experiment 1, short-term altrenogest treatment combined with equine chorionic gonadotropin (eCG) and human chorionic gonadotropin (hCG) was used to attempt synchronization of follicular development. In Experiment 2, the effects of superstimulation (1000 or 1500 IU eCG), day post-weaning, and two aspiration flow rates of 24 and 30 mL of water per minute were evaluated. In Experiment 3, OPU-derived oocytes collected 10-14 h or 34-36 h after hCG administration were subjected to IVEP to assess the effect of partial in vivo maturation. RESULTS: In Experiment 1, altrenogest-based synchronization was associated with low oocyte recovery in several animals. In Experiment 2, a mean of 30.3 ± 11.0 oocytes per OPU session was recovered from 54.8 ± 10.6 aspirated follicles, corresponding to a recovery rate of 55.3%. No significant differences were detected between the two aspiration flow rates or between superstimulation treatments. In Experiment 3, partially in vivo matured oocytes resulted in a 33% blastocyst rate, compared with 6% following full in vitro maturation. CONCLUSIONS: These results demonstrate that transvaginal OPU in sedated, epidurally treated sows can yield substantial numbers of oocytes under field conditions. Partial in vivo maturation prior to IVEP was associated with improved blastocyst rates. Further controlled studies are required to optimize synchronization protocols and to improve repeatability of oocyte retrieval and IVEP.