Biological and economic consequences of introgession of the FecB gene into the Frenche Mérinos d'Arles sheep

The information analysed comes from three datasets collected on an experimental farm ('Le Merle') where the Booroola gene was first introgressed into the Merinos d'Arles breed in 1983, and a private farm where Booroola-carrier ewes were bred for production. Reproduction (ovulation rate, litter size, survival rate) and production (body weight, carcass weight, dressing percentage) traits were compared between B+ and ++ animals as well as controls from the Merinos d'Arles breed. The increase in ovulation rate caused by the Booroola gene had a dramatic effect on litter size at birth, and consequently changed the survival and growth of the lambs. Globally, B+ ewes were able to produce about 50-65% extra lambs, the result being consistent across comparisons. Efforts are now under way by the breeders to exploit the gene at a higher level. (Resume d'auteur)