Effects of transport seasons on stress and meat quality of pigs

Abstract: Pre-slaughter stress is both an animal welfare issue and a quality issue, as it has long been recognized that pre-slaughter stress can adversely affect the quality of pork. Pre-slaughter handling includes mixing of unfamiliar animals, loading, unloading, transportation and abattoir lairage. All these handling practices can induce stress. Transport season is a crucial factor governing the amount of animal stress and influencing the meat quality. It is known that cold and heat stress have an impact on ante-mortem and post-mortem muscle glycogen stores leading to higher incidence of DFD (dark, firm, dry) and PSE (pale, soft, exudative) pork respectively. Several studies on the effects of transport season on meat quality have been reported in the countries like UK or Denmark, where the climate conditions are relatively stable, but few studies was reported in regions of large temperature difference, and did not mention animal stress. In order to investigate the effects of transport seasons on the animal stress and meat quality of pigs, a total of sixty Duroc × Large White × Landrace pigs came from the same farm were transported in summer, autumn and winter in Beijing. The carcass skin blemish, blood biochemical parameters and blood constituents as the indicators of animal stress and the meat quality traits of pH value, temperature, color, drip loss, cooking loss and shear force were measured in this sutdy. The results showed that pigs transported in autumn presented lower white blood cells, hemoglobin, hematocrit, adrenocorticotrophic hormone, cortisol and glucose in blood compared with summer and winter (P<0.05). Carcass skin blemish scores were lowest in pigs transported in autumn (P<0.05). Plasma enzymatic activities of creatine kinase and lactic dehydrogenase were significantly higher in summer than the other groups (P<0.05). Lactate, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration and platelet count were not significantly different among the three groups (P>0.05). With the exception of b* and muscle temperature at 24h postmortem, transport seasons significantly influenced other meat quality parameters (P<0.05). Compared with autumn, pigs transported in summer showed significant higher muscle temperature at 45min postmortem, drip loss, cooking loss and L* value, the shear force and a* value dramatically reduced (P<0.05), while a* color coordinate value significantly increased in winter (P<0.05), drip loss and shear force had no significant difference (P>0.05). The research identified that the proper transport season for the test pigs in Beijing was autumn, both from the viewpoint of animal welfare and meat quality. Pigs transported both in summer and winter presented higher stress and worse meat quality. In conclusion, more attention should be paid to the effect of transport seasons on stress and meat quality in pigs in order to improve the animal welfare and obtain better pork quality.