Transfer of frozen-thawed embryos in sheep.

Embryos collected from ewes six days after oestrus were frozen in straws using ethylene-glycol as a cryoprotectant. The efficiency of the simplified freezing and thawing procedure was assessed after transfer, which resulted in an overall survival rate of 58.3 per cent. Forty-two lambs were born from 72 frozen embryos which had been transferred without any attempt to evaluate them after the thawing and sucrose dilution process.