Repeated endoscopic ovum pick-up in hormonally untreated ewes: a new technique

Multiple ovulation and embryo transfer (MOET) are cumbersome and may not be used in all animals. An alternative method for obtaining embryos is to harvest ova and subject them to in vitro maturation/fertilization (IVM/IVF). We tested a modified endoscopic technique designed to allow repeated recovery of oocytes from donor ewes without any hormonal treatment. Seventeen randomly chosen Merino donors were used for ovum pick-up 5 times (OPU1 to OPU5) at 1-wk intervals. The OPUs were performed by ventral laparoscopy. The follicular fluid was aspirated through a needle (0.9 x 75 mm) connected to a 5 ml-syringe. A total of 385 oocytes was collected from 567 aspirated follicles for a collection rate of 67.9%. The number of follicles and oocytes per ewe and the collection rate did not differ significantly (P > 0.05) between collection periods; however, a large variability in the number of follicles and oocytes was observed among individual animals. The collection rate tended to be higher in donors which showed a higher number of follicles. Possible reasons for this are discussed. Oocytes were divided into 4 classes based upon morphological criteria. The portion of oocytes suitable for in vitro production (Classes I to III) were similar among collection periods (83% in OPU1 vs 84% in OPU5). The technique described in this study is useful for obtaining large numbers of oocytes from individual animals during a defined period. This method combined with established in vitro production programs provides a way to increase the number of offspring from genetically valuable animals even when they are affected by infertility due to adhesions or deformations of the oviduct and/or uterus.