Background

Handling of pigs prior to slaughter is critical for obtaining good pork quality. It is recognized that stress exposure during this process is a key factor causing huge variations in meat quality, which cause economic loss for the meat industry. Stress exposure will affect the glycogen content as well as the rate of glycolysis and hence the pH development post mortem, and it has been found that pH and temperature measured early post mortem are good indicators for the subsequent meat quality development. However, the basic mechanisms at the cellular level involved in the post mortem processes are still far from fully understood. An understanding of how the muscle cells respond to stress exposure before slaughter as well as the post mortem conditions would be extremely helpful for the overall understanding of how these conditions affect the meat quality. An increased knowledge of these basic cellular responses would contribute to optimising the handling of slaughter pigs, thereby ensuring an optimal meat quality and reduce economic loss in the pork industry.

The cellular events that are initiated in muscle cells by slaughtering are complex. Slaughter pigs are withdrawn from feed prior to slaughter and furthermore exposed to stressful conditions related to transport and slaughter, which will activate a release of stress hormones (adrenaline/cortisol). Because of these conditions the muscle cells are in a state of starvation, and therefore dependent on endogenous fat oxidation and high activity in the mitochondrial respiratory chain, which is the site of oxidative stress formation, and may thus increase stress susceptibility. In addition, due to termination of the blood supply, the situation post mortem is associated with a combined energy and oxygen deprivation (anoxia/ischemia). Using primary porcine muscle cell cultures, the present study aims at investigating the cellular responses triggered by these events. Satellite cells are isolated from pigs and cultured to form fully differentiated poly-nuclear myotubes. Thus, these cells are not subjected to any form of manipulation and is regarded the closest model system facilitating strictly controlled conditions and thereby enable to study these mechanisms comprehensively.