Presence of causative mutations affecting prolificacy in the Noire du Velay and Mouton Vendéen sheep breeds

•The Lacaune FecLL prolific mutation also segregates in the Noire du Velay sheep.•The Grivette FecXGr prolific mutation also segregates in the Mouton Vendéen sheep.•FecLL and FecXGr prolific alleles increase litter size by +0.3 to +0.4 lamb/lambing. For many decades, prolificacy has been selected in meat sheep breeds as a polygenic trait but with limited genetic gain. However, the discovery of major genes affecting prolificacy has changed the way of selection for some ovine breeds implementing gene-assisted selection as in the French Lacaune and Grivette meat breeds, or in the Spanish Rasa Aragonesa breed. Based on statistical analysis of litter size parameters from 34 French meat sheep populations, we suspected the segregation of a mutation in a major gene affecting prolificacy in the Noire du Velay and in the Mouton Vendéen breeds exhibiting a very high variability of the litter size. After the genotyping of mutations known to be present in French sheep breeds, we discovered the segregation of the FecLL mutation at the B4GALNT2 locus and the FecXGr mutation at the BMP15 locus in Noire du Velay and Mouton Vendéen, respectively. The frequency of ewes carrying FecLL in the Noire du Velay population was estimated at 21.2% and the Mouton Vendéen ewes carrying FecXGr at 10.3%. The estimated mutated allele effect of FecLL and FecXGr on litter size at +0.4 and +0.3 lamb per lambing in Noire du Velay and Mouton Vendéen, respectively. Due to the fairly high frequency and the rather strong effect of the FecLL and FecXGr prolific alleles, specific management programmes including genotyping should be implemented for a breeding objective of prolificacy adapted to each of these breeds.