Repeated superovulation and surgical recovery of embryos in the ewe

Repeated superovulation using three treatments of pFSH at intervals of 45 to 55 days during the same breeding season was carried out in 18 Préalpes ewes. The embryos were recovered by surgery after the first two treatments and by slaughter after the last one at Day 6. Three lots of control ewes (n = 5 or 6) receiving the same superovulation treatment were slaughtered respectively at the same time. The first and third repeated superovulation treatments gave averages of 5.2 +/- 0.6 and 4.5 +/- 0.6 corpora lutea. The second one gave 3.4 +/- 0.4 corpora lutea, which was significantly lower than with treatments 1 and 3, but adhesions did not permit a perfect view of the whole surface of the ovaries. Recovery rates decreased regularly with repeated collection (88.2, 52 and 24%, respectively). The proportion of embryos at the morula/blastocyst stage also decreased from 86 and 93% to 6.7% at the third treatment. The development of post-surgical lesions probably caused variations in the apparent rate of ovulation and a decrease of egg recovery and fertilization rates. In control ewes the mean level of superovulation did not vary significantly during the breeding season and embryonic development was normal when checked at slaughter. Repeated superovulation using pFSH is worthwhile only if the eggs are recovered by perfusion with an appropriate catheter (introduced into the uterus by laparoscopy) instead of by surgery.