Two single nucleotide polymorphisms in the promoter of the ovine myostatin gene ( MSTN ) and their effect on growth and carcass muscle traits in N ew Z ealand R omney sheep

Summary Myostatin is a negative regulator of muscle growth and development in mammals, and variation in ovine myostatin gene ( MSTN ) has been demonstrated to be associated with variation in the muscularity of sheep. Polymerase chain reaction–single‐stranded conformational polymorphism ( PCR – SSCP ) was used to look for single nucleotide polymorphisms ( SNP s) in a 304‐bp amplicon from the promoter region of ovine MSTN . Sequence analyses revealed two previously identified SNP s (c.−2449 G / C and c. −2379 T / C ) that resulted in three haplotypes ( H 1 (c.[−2449 G ; −2379 C ]), H 2 (c.[−2449 C ; −2379 C ]) and H 3 (c.[−2449 G ; −2379 T ]). The effect of these SNP s on growth and carcass traits was investigated in 357 NZ R omney lambs. General linear mixed‐effect models revealed that sheep with the genotype c.−2449 GC had a higher loin meat yield (p = 0.032) and proportion loin yield (p = 0.028), than those with the genotype c.−2449 GG . The genotype c.−2379 CC was associated with an increase in three weight traits: birthweight (p = 0.003), tailing weight (p = 0.009) and weaning weight (p = 0.028), when compared with the genotype c.−2379 TC , but it was not found to have an association with growth rate. This suggests that c.−2379T/C has an effect that originates at, or before birth. Haplotype H 3 was associated with a decrease in birthweight (p = 0.002), tailing weight (p = 0.003) and weaning weight (p = 0.011). Haplotype H 2 was associated with increased loin yield (p = 0.012) and proportion loin yield (p = 0.002). The SNP s may have value as genetic markers for improved R omney breeding.