Effects of the myostatin F94L substitution on beef traits

¹ School of Agriculture, Food and Wine, University of Adelaide, Roseworthy SA 5371 Australia
² AgResearch, Ruakura Research Centre, PB 3123, Hamilton, New Zealand

^* To whom correspondence should be addressed. E-mail: Wayne.Pitchford{at}adelaide.edu.au.

	Abstract

This study investigated the effects of a single nucleotide polymorphism (SNP) in the myostatin gene (MSTN or growth differentiation factor 8, GDF8) on birth, growth, carcass and beef quality traits in Australia (Aust.) and New Zealand (NZ). The SNP is a cytosine (C) to adenine (A) transversion in exon 1, causing an amino acid substitution of leucine for phenylalanine⁹⁴ (F94L). The experiment used crosses between the Jersey and Limousin breeds, with the design being a backcross using first-cross bulls of Jersey x Limousin or Limousin x Jersey breeding, mated to both Jersey and Limousin cows. Progeny were genotyped for the myostatin SNP and phenotyped in Aust. with finishing on feedlot (366 animals, over 3 birth yr) and in NZ with finishing on pasture (416 animals, over 2 birth yr). The effect of the F94L allele (A allele) on birth and growth traits was not significant. The F94L allele in Limousin backcross animals was associated with an increase in meat weight (7.3% and 5.9% of the trait mean in Aust. and NZ, respectively, P < 0.001), and a reduction in fat depth (-13.9% and -18.7% of the trait means on live animals (600 d) and carcasses, respectively, Aust. only, P < 0.001), intramuscular fat content (-8.2% of the trait mean in Aust., P < 0.05; -7.1% in NZ, not significant), total carcass fat weight (-16.5% and -8.1% of the trait mean, Aust. and NZ; P < 0.001 and P < 0.05, respectively). Meat tenderness, pH and cooking loss of the M. longissimus dorsi were not affected by the F94L variant. In the Jersey backcross calves, additive and dominance effects were confounded, because the F94L allele was not segregating in the Jersey dams. The combined effects, however, were significant on loin eye muscle area (4.4% in both Aust., P < 0.05, and NZ, P < 0.01), channel fat (-11.7%, NZ only, P < 0.01), rib fat depth (-11.2%, NZ only, P < 0.05) and carcass fat weight (-7.1%, NZ only, P < 0.05). The results provide strong evidence that this myostatin F94L variant provides an intermediate and more useful phenotype than the more severe double-muscling phenotype caused by knockout mutations in the myostatin gene.

Key Words: beef cattle, carcass traits, GDF8, F94L, meat quality, myostatin