Some factors affecting pregnancy rate in ewes following laparoscopic artificial insemination

The fertility of 646 ewes and gimmers bred by laparoscopic artificial insemination (LAI) in the autumn of 2006 was investigated using a questionnaire and individual ewe breeding records kept for 13 commercial sheep flocks that used LAI routinely. Overall, the pregnancy rate was 66 per cent, but it was highest in ewes bred for the fourth time. Technical aspects of LAI influenced fertility: pregnancy rates were 70 per cent for ewes bred using frozen semen compared with 58 per cent when fresh semen was used (P≤0.01), and 74 per cent of ewes that travelled to an artificial insemination centre for mating conceived, compared with 62 per cent that remained on their own farm (P<0.01). Higher doses of equine chorionic gonadotrophin (>400 iu) used for oestrus synchronisation reduced pregnancy rates to only 49 per cent (P<0.001). However, the largest effect was associated with shepherds gathering, handling and treating breeding ewes four to six weeks before mating; pregnancy rates were 54 per cent among ewes where this was carried out, compared with 74 per cent for ewes not treated in this way (P<0.01).