The results are described of transfers of ova between sheep.
Where necessary, treatment with progesterone was used to synchronize the heats of donor and recipient ewes. pms was used to increase the number of ova shed by donor ewes. Data are given on the onset of heat after treatment in donor and recipient ewes and on the numbers of ova shed, recovered and fertilized among donor ewes.
Of a total of fifty transfers, twenty-six were successful; most of the successful transfers were made to untreated recipients and to treated recipients in which transfer was delayed until the second heat after treatment with progesterone.
Factors that may have affected the success of transfers were: failure to synchronize heats of donors and recipients; the transfer, in progesterone-treated ewes, of ova at the first cycle after treatment; omission of antibiotics from the serum used for recovery, storage in vitro and transfer of ova; the clinical (scrapie) history of the experimental ewes.
There was no evidence of any effect of the time of storage in vitro (up to 5½ hr) on the success of transfers among ova transferred on the day of recovery.