We have previously reported that a single-nucleotide polymorphism (SNP) on the large subunit of micro-calpain (the calcium-activated neutral protease-1 gene) is associated with differences in tenderness, as measured in cooked steaks from the longissimus dorsi of animals from the AgResearch Jersey-Limousin Beef DNA-marker trial. The effect was significant at the intermediate stages of the tenderising process and had little effect on initial or ultimate tenderness, so that tenderising was accelerated in animals having one or two copies of the favourable variant. We have now analysed tenderness and genotype data from 310 additional animals, comprising Hereford-cross and pure Angus breeds slaughtered under varying conditions of electrical stimulation and aged at a range of temperatures. Results in all cases support the original finding: animals with two copies of the `C` allele (the SNP on Exon-9 encoding alanine at amino acid number 316) have more tender meat (decreased shear force) at the intermediate stages than animals with two copies of the `G` allele (encoding glycine). Combining measurements from three intermediate cook times, mean shear forces from `CG` were less than from `GG` genotypes by 0.80 ± 0.29 kg (P < 0.01), and mean shear forces from `CC` were less than from `CG` genotypes by 1.19 ± 0.36 kg (P < 0.001). These results show that a genotype substitution from `GG` to `CC` is associated with a difference in shear force in longissimus dorsi steaks of approximately 20% at intermediate aging times. KEYWORDS: cattle; meat; tenderness; micro-calpain; SNP.

NG, Cullen, CA Morris, BA Veenvliet, SM Hickey, PM Dobbie, and T Wilson

Proceedings of the New Zealand Society of Animal Production, Volume 65, Christchurch, 266-270, 2005
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