Variability in tenderness remains a major concern to the meat industry, and our objective was to identify genetic effects on beef meat tenderness, in animals treated alike, and under similar post-mortem processing conditions. A quantitative trait locus (QTL) for beef tenderness has been located on the same region of chromosome 29 in a United States Department of Agriculture (USDA) study and in our research. Micro-calpain, or calcium-activated neutral protease (CAPN1), has been identified as a candidate gene. The calpain/calpastatin system is involved in the change of tenderness with time, by regulating post-mortem proteolysis. The CAPN1 gene was sequenced by USDA workers who identified single-nucleotide polymorphisms (SNPs) in two exons. These results were followed up as part of the AgResearch Jersey-Limousin Beef QTL trial, where steak samples were obtained from the longissimus dorsi of 416 animals slaughtered at about two years of age. The segregating USDA and NZ families were both heterozygous for one of these SNPs, on exon 9, and this region was predicted to alter the protein sequence by the substitution of alanine for glycine in Domain II. Both families were genotyped for these two SNPs, as well as for six intronic polymorphisms, to define haplotypes. Analysis of tenderness measurements in the NZ data (n=81 animals) showed a difference between paternal CAPN1 haplotypes, with the SNP encoding alanine at amino acid number 316 being associated with more tender meat (decreased shear force) relative to the SNP encoding glycine (P<0.00001). The association of the maternal haplotypes with meat tenderness phenotypes (P<0.01) was also consistent with the hypothesis of CAPN1 as the gene underlying the QTL effect. The sire and dam effects together accounted for over 30% of the residual variance in tenderness. Our results show that a single SNP test in the laboratory can distinguish genetically tender and genetically tough animals at any age.

NG, Cullen, BT Page, CA Morris, SM Hickey, and PM Dobbie

Proceedings of the New Zealand Society of Animal Production, Volume 63, Queenstown, 53-56, 2003
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