Estimated frequencies of myostatin mutations (double muscling) in Australian tropically adapted beef breeds.

Abstract

Myostatin mutations have been identified in many beef breeds and have been associated with increased carcase yields, reduced fat, increased calving difficulty, delayed puberty and reduced female fertility. This study aimed to estimate the allele frequencies of myostatin mutations in Australian tropically adapted beef breeds. Nine myostatin variants (viz. C313Y, D182N, E226X, E291X, F94L, NT419, NT821, Q204X and S105C) were assessed in Brahman (n=2,554), Droughtmaster (n=2,188), and Santa Gertrudis (n=904) cattle that were part of the Repronomics research project. Results showed the myostatin variants NT821 and F94L were segregating in the Droughtmaster and Santa Gertrudis breeds but not in the Brahman. In total, 17.4% and 26% of Droughtmaster and Santa Gertrudis animals carried at least one copy of a myostatin allele for either variant. The frequency of the NT821 allele was 0.08 and 0.12, and the F94L allele was 0.01 and 0.02, respectively, for Droughtmaster and Santa Gertrudis animals. Hardy-Weinberg equilibrium was observed for both NT821 and F94L in both breeds. However, there were fewer than expected two copy NT821 animals for both breeds. With no variants detected in Brahman, the myostatin variants likely originated from the Bos Taurus influence of the Droughtmaster and Santa Gertrudis breeds. The allele frequencies of NT821 in the Droughtmaster and Santa Gertrudis breeds, along with the literature reports of increased calving difficulties associated with NT821, indicate that breeders should monitor and manage the presence of the NT821 myostatin variant. Further research should be undertaken to quantify the size of the effect that having one and two copies of the mutation has across all economically important traits.