Abstract: The objectives of this study were to verify the pleomorphic distribution of FecB gene in the ternary hybrid sheep of Germany Mutton Merino sheep×small-tailed Han sheep×fine-wool sheep, and to assess its correlation with lambing performance of the ternary hybrid sheep. German Mutton Merino sheep and the F₂ hybrid sheep produced with small-tailed Han rams and northeast fine-wool ewes were used as the male parent and female parent, respectively, to produce the ternary hybrid sheep. The KASP method was used to analyze the genotype of FecB, and its gene frequency and genotype frequency were calculated. Furthermore, the correlation of gene frequency of FecB with the lambing performance of the ternary hybrid sheep flock was assessed. FecB gene was absent in German Mutton Merino sheep. The B allele frequency of the ternary hybrid sheep was increased significantly and was in a Hardy-weinberg imbalance state, indicating that the artificial selection had a great impact on FecB gene enrichment in hybrid sheep. The rank-sum test analysis on litter size of the individuals of F₂ hybrid ewes and ternary hybrid sheep with different genotypes demonstrated the P value were all less than 0.01, and for the two sheep flocks, the average lambing rate of the individuals with ++ genotype was both lower than those with B+ and BB genotypes （P<0.05）. It is indicated that the B allele play an important role in improving lambing performance of the ternary hybrid sheep. This study provides a reference for ameliorating the lambing performance of the ternary hybrid sheep using FecB gene.

Key words: FecB gene, KASP method, lambing performance, ternary hybrid sheep of Germany Mutton Merino sheep×small-tailed Han sheep×fine-wool sheep