OVUM TRANSFER IN THE SHEEP

Abstract

SUMMARY Transfers were made of 127 fertilized sheep ova to ninety-one ewes in which oestrus had been detected 1–4½ days previously. Fifty-two ewes received ova of the 6- to 16-cell stage, and forty-one of these (78·8%) gave birth to one or more lambs. Transfers were most successful where oestrus was synchronized between donor and recipient. Some sheep ova were successfully transferred after storage in vitro at between 30 and 37°C for up to 115 min. Ova at the 6-to 16-cell stage developed more frequently in ewes which had more than one corpus luteum in their ovaries at the time of transfer; of ova transferred singly 74%, and of ova transferred in pairs 75% developed into lambs. No 2-cell ova, and only 15·8% of 4-cell ova, developed when transferred into the uterine cornua, and no 2- or 4-cell ova developed when transferred into the uterine tubes of ewes in which oestrus had commenced more than 3 days prior to transfer. The success of individual transfers was not significantly related to the breed of the recipient ewe, breed origin of the ovum, the season in which transfer was performed, or to the number and result of previous transfers made into the same recipient. Out of thirteen ewes subjected to one or more transfers of ova, twelve subsequently conceived after matings at their first or second heat in the season of transfer.