The average twin lambing rate of Bayanbulak sheep is 2% to 3%. However, a flock of sheep with a close genetic relationship and an average of 2 to 3 lambs per birth has been found recently. To determine the major genes controlling the prolificacy of the flock in the present study, the flock was designated A while 100 normal Bayanbulak sheep were randomly selected to comprise the control flock B. Ligase detection reaction method was applied to detect and analyze the 10 mutational loci of the 3 candidate prolificacy genes including bone morphogenetic protein type I receptors, bone morphogenetic protein 15, and growth differentiation factor 9. The 10 mutational loci are as follows: FecB locus of the BMPR-IB gene; FecXI, FecXB, FecXL, FecXH, FecXG, and FecXR of the BMP15 gene; and G1, G8, and FecTT of the GDF9 gene. Two mutations including BMPR-IB/FecB and GDF9/G1 were found in Bayanbulak sheep. Independence test results of the two flocks demonstrate that the FecB locus has a significant effect on the lambing number of Bayanbulak sheep. However, the mutation frequency of the G1 locus in GDF9 is very low. Independence test results demonstrate that the GDF9 locus does not have a significant impact on the lambing performance of Bayanbulak sheep. Among the 10 detected loci, BMPR-IB/FecB is the major gene that influences the high lambing rate of Bayanbulak sheep.

The involvement of melanocortin 4 receptor gene (MC4R) in food intake and body weight regulation is well characterized. MC4R mutations are the most frequent monogenic cause of human obesity. Significant associations have been revealed between MC4R mutations and productive traits in pigs, cattle and poultry. Herein, fluorescence-based conformation sensitive gel electrophoresis was used to identify two single nucleotide polymorphisms (SNPs) in the coding region (93G>A and 292G>A) and two SNPs in the 3'-UTR area (1016G>A and 1240T>C) of MC4R gene in 132 German Merino sheep. We found that the 1016G>A mutation in the 3'-UTR was significantly associated with body weight at 120 and 180 days, average daily gain, back fat thickness and loin-eye area. Allele A located at the 292th position of MC4R gene representing Arg98 was associated with significantly higher loin-eye area in sheep. For the synonymous 93G>A mutation, A allele carrier animals had higher back fat thickness. Our results provide evidence that the MC4R gene may be a candidate gene for growth and meat quality traits with MC4R SNPs being potentially valuable as genetic markers for economic traits in German Merino sheep.