Effects of single nucleotide polymorphisms identified at the μ-Calpain and Calpastatin gene locus on tenderness of meat from commercial cattle
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A total of 102 crossbred cattle from commercial herds with Bos taurus indicus influence (CCP) and 22 crossbred Bos taurus taurus (Senepol x Charolais) from the UPR herd (UPRCP) were evaluated for meat quality and genotyped for candidate markers in the CAPN1 and CAST genes. The Bos taurus indicus influence in the commercial group was detrimental to overall tenderness with a mean of 9.15 kg in Warner Bratzler Shear force (WBS) 24h postmortem. Low free calcium concentrations among the CCP at 24h and 14d post mortem (53.97 ± 19.29 and 64.11 ± 26.91 μM respectively) could have contributed to the high WBS. High ultimate pH values (5.75) in the CCP also suggest that long term stressors, during the handling procedures prior to slaughter, may have influenced this result. Acceptable tenderness (4.6 kg WBS) was achieved in a pasture-fed system used with the locally adapted Bos taurus taurus group. A positive correlation between WBS at 24h postmortem and free calcium concentration at 24h (r = 0.52) and 14d (r = 0.33) postmortem was observed in the CCP. Older animals with 8 permanent teeth showed increased tenderness in combination with little change in free calcium concentration from 24h to 14d postmortem (39 μM and 48 μM respectively) and the highest ultimate pH values (6.09). These results in the order animals, contrary to those in the other age groups, could be credited to a sarcopenic phenotype observed as increased muscle wasting due to altered calcium homeostasis, depleted muscle ATP content and activation of the calpain system and other apoptotic pathways (Bartoli et al., 2005; Andersson et al., 2011). A total of 26 SNP were genotyped from the CAPN1 and CAST genes in both populations, of which 16 were previously identified and 11 were newly found. Low frequencies of the desirable tender meat genotype (less than 0.05%) were observed in the CCP among the commercially available SNP markers 530, 316, 4753 and 5331 in the CAPN1 gene. Only the CAPN1 316 marker produced a -4.72 kg change in WBS 24h when the CC genotype segregated in the CCP. Low frequencies were also observed among the other SNP evaluated in the CAPN1 gene. Despite this low frequency, differences in WBS of -5.14 kg, -5.30 kg and - 7.74 kg were observed when the GG, TT and INS C genotypes found in introns 8 and 9 of the CAPN1 gene segregated in SNPs 430, 573 and 643 respectively. The UPRCP segregated higher frequencies of the tender genotype in almost all SNP from the CAPN1 gene, but significant differences in tenderness were observed in only two of those found in intron 14 of this gene. SNP 209 genotype AA produced an increase of 45.45 in MFI and SNP 351 genotype GG produced a difference of -3.35 kg in WBS. Among the SNP studied in the CAST gene higher frequencies of the tender genotype were observed (greater than 45%) for markers 282, 2959 and 3016 in both populations. A significant difference in tenderness was found only in CAST 2959 (-2.33 kg in WBS) when the AA genotype segregated in the UPRCP. In this investigation two candidate markers for determining tenderness were found in intron 14 of the CAPN1 gene in cattle with mostly Bos taurus taurus influence. Polymorphisms in introns 8 and 9 of the CAPN1 gene show greater effect on tenderness in the Bos taurus indicus population although their frequencies were greater in the Bos taurus taurus population.