Pre-slaughter handling and selected genotypic traits modulate proteolytic enzymes and pork tenderness during 24 h post-mortem

Context The effects of changes in pork during the first 24 h post-mortem may influence the quality and tenderness of the meat before it is delivered to end-users. Aim We investigated the effects of different pre-slaughter handling practices in pigs on meat quality, tenderness, and muscular proteolytic enzymes in the first 24 h post-mortem, in relation to selected genotypic traits. Methods Ninety barrows with a similar genetic line and a similar feed composition were raised separately on two farms located in Nakhon Ratchasima (NR) province, Thailand (60 pigs, groups A and C of 30 pigs each) and Khon Kaen (KK) province, Thailand (30 pigs in group B). At live commercial slaughter weight, all 90 pigs were transferred and processed at two abattoirs in KK province (groups A and B) and Lopburi (LB) province, Thailand (group C), which had different slaughtering facilities. The longissimus thoracis et lumborum (LTL) muscle samples from all groups were determined for pH at 1, 6 and 24 h, proteolytic enzymes; calpain 1 (μ-calpain), cathepsin and calpastatin, drip loss, shear force and panel testing in humans. Key result Pre-slaughter handling significantly affected post-mortem proteolytic enzyme activity, with handling stress altering μ-calpain and calpastatin dynamics. Enzyme activities were associated with tenderness outcomes; however, causal relationships cannot be inferred from this observational design. Genetic variation in calpastatin exerted a stronger influence on tenderness than environmental stressors, suggesting locus-specific effects. Overall, the interaction between genotype and pre-slaughter factors modulated enzymatic proteolysis, indicating calpastatin polymorphisms as potential markers for pork tenderness. Conclusion Post-mortem pH dynamics critically regulate enzymatic proteolysis, driving pork tenderness and water-holding capacity. Pre-slaughter stress and slaughter methods shaped these processes, with slower pH decline and higher ultimate pH enhancing meat quality. Genetic variation in calpastatin may exert a stronger influence on tenderness than pre-slaughter environmental stressors under the conditions studied. Implications The results suggest that combining improved slaughter practices with genetic selection for calpastatin variants offers a practical strategy for producing consistently high-quality pork.