FecB mutation and litter size are associated with a 90-base pair deletion in BMPR1B in East Friesian and Hu crossbred sheep

Litter size is a critical economic trait in livestock, but only a few studies have focused on associated indel mutations in BMPR1B, a key regulator of ovulation and litter size in sheep. We evaluated the effects of BMPR1B mutations on the reproductive performance of sheep. We used Hu, East Friesian, and East Friesian/Hu crossbred sheep as experimental subjects and identified a novel 90 bp deletion in BMPR1B, which coincides with the c.746A > G (FecB mutation) genotype. The correlation between the two loci and litter size was then evaluated. We identified three genotypes for the Del-90bp locus, namely, II, ID, and DD, and three genotypes for the c.746A > G locus, namely ++, B+, and BB. Both Del-90bp and c.746A > G significantly affected the litter size of Hu and East Friesian/Hu crossbred sheep. Linkage disequilibrium analysis revealed a strong linkage disequilibrium between these loci in Hu sheep and the F1 population (r(2) > 0.33), which suggests that detecting this 90 bp deletion might be a simple method to identify the likely carriers of c.746A > G. However, the function of this 90-bp deletion still needs further exploration. We provide genetic data that can be used as a reference for the breeding of improved prolific traits in sheep.