Identification and quantification of calpain complex and its relation to the quality meat in Nellore cattle

The role of proteolytic enzymes during the post mortem has been reported as a major determining factor in the quality of the meat. The enzymes calpain and calpastatin are one of the main agents in this process. Therefore, this study aims to evaluate the protein quantification of calpain 1 (CAPN1), calpain 2 (CAPN2) and calpastatin (CAST) in order to assess the quality of meat in Nellore cattle. Ninety not castrated male were kept on pasture until they reach 390 ? 37 kg and 24 months of age. The animals were weighed at the beginning of the feedlot period and every 28 days until slaughter with the purpose to obtain the records the gain weight (GW) and slaughter weight (SW). After slaughter, samples of the Longissimus thoracis muscle were removed for shear force (SF), myofibrillar fragmentation index (MFI) and western blot analysis. Four groups (n = 12 animals / group) were separated according to the combination of two factors: growth (GW and SW) and meat texture (SF and MFI), thus, the following groups were formed: small tender meat (STM), small tough meat (STHM), large tender meat (LTM) and large tough meat (LTHM). Total protein was extracted from skeletal muscle samples of the animal group. The western blot reactions were performed using primary antibodies AB3589 (CAPN1), AB713 (CAPN2) and MA3-945 (CAST). Statistical analysis was done using linear mixed models for quantification of proteins. The means for GW were 136.0, 131.9, 187.1 and 177.0 and for SW were 505.6, 520.25, 599.38 and 592.0 while the means for SF were 4.4, 7.1, 4.7, 6.9 and for MFI were 58.5, 41.3, 62.9 and 44.1 for the STM, STHM, LTM and LTHM groups, respectively. No significant differences (P> 0.05) were observed in quantification of CAPN1, CAPN2 and CAST among the four two groups studied. It was observed statistical difference between the ratio of CAPN1 to CAST for the STM group and STHM, LTM and LTHM groups. It was found correlation between the ratio of CAPN1 to CAST and SF (rp = 0.46; p<0.05). The results showed that for Nellore cattle the use of the potential of quantification of proteolytic enzymes to the meat tenderness traits can be through the ratio of CAPN1 to CAST.