Breeding and Genetics: Beef Cattle

The association of a single nucleotide polymorphism (SNP) of calpain 1 (CAPN1) gene with shear force of 2.54 cm steaks from M. longissimus dorsi from Gannan yaks (Bos grunniens, n = 181) was studied. The experimental design was a repeated measures with the main unit in a completely randomized design with a factorial arrangement of treatments (age at harvest x SNP) and the repeated subunit was aging days. Individual animal was used as the experimental unit. Yaks were harvested at 2, 3, and 4 yr of age (n = 51, 59, and 71, respectively), and samples of each yak carcass were aged at 4°C for 0, 1, 3, 7, 14 or 21d. Shear force for each sample was determined at each of 6 postmortem aging times using Warner-Bratzler shear force methodology. Fragments of the yak CAPN1 gene including exon 9 and intron 9 were amplified and subjected to single strand conformation polymorphism analysis. A SNP was found within intron 9 of the CAPN1 gene G5837A, and there were 2 genotypes of GG and GA identified, respectively. The genotypic frequency of GG was 82.87% compared with 17.13% for GA. Statistical analysis was done using SAS PROC MIXED. Interaction of SNP × age at harvest × aging days was demonstrated (P < 0.10) for shear force. In 2-yr-old yak, genotype GG had lesser shear force than that of GA at the aging times of 0, 3, and 7 d (0.78, 0.92, and 0.65 kg, respectively; P < 0.05); however, in 3-yrand 4-yr-old yak, genotype GG had lesser shear force than GA at aging time of 14 d (0.71 and 0.58 kg, respectively; P < 0.05). Genotype had little effect (P > 0.05) on shear force for 3and 4-yr-old yaks averaged over aging time. In 2-yr-old yak, genotype GG had 0.57 kg lesser shear force than yaks with genotype GA (P < 0.05) averaged over aging time. Therefore, results from this research suggest that the CAPN1 SNP affected shear force of M. longissimus dorsi but the effect differed depending on age of yak and aging time of the meat.