Effects of transportation time and temperature on pig stresses and pork quality

Because of the pig stress, 20 000 tons of PSE (pale soft exudative) and DFD (dark firm dry) meat were engendered in Beijing every year. Transportation time and temperature were studied, since other factors which caused pig stress made no difference in Beijing. In order to investigate the effects of different transportation time (0, 3, 6, 9 h) and temperature (-10?0℃, 0?10℃, 10?20℃, 20?30℃) on pig stress and pork quality, a total of 84 Duroc × Landrace Large × White barrows were transported to the same abattoir, and the barrows had been raised up to (104±4) kg by the same person. The transportation speed was 60?70 km/h and the transportation density was 2.2 pigs per square meter. The pigs were transported without stops. During loading and unloading, in the farm and at the abattoir the pigs were gently handled, and no whips and electric prods were used. No food was available while the water was continually available during the transportation. The pigs were stunned electrically with 125 V on head and 75 V on heart. The blood constituents were used as the indicators of pig stress, and the pork quality traits including the pH values 45 min and 24 h after slaughter and the pork color grade were measured in this study. The results showed that the alanine aminotransferase (ALT) in blood plasma after 6 h transportation increased significantly (P<0.05) compared to that after zero and 3 h transportation, which meant the pigs presented stress reaction after 6 h transportation, and the ALT, aspartate transaminase (AST), lactate dehydrogenase (LDH), cortisol (COR) after 9 h transportation increased significantly (P<0.05) compared to those after zero, 3 and 6 h transportation, which meant the stress was significantly stronger after 9 h transportation. The pork pH values 45 min after slaughter through 6 and 9 h transportation were significantly lower than those after 3 h transportation (P<0.05). In the same time, the pork color grades (above 4) were significantly higher than those after 3 h transportation (P<0.05) which caused the pork quality to decrease. Pigs presented stress reaction when they were transported at the temperature of under 10℃ since the AST and alkaline phosphatase (ALP) increased significantly (P<0.05), and the stress was significantly stronger when they were transported at the temperature of under 0℃ since the creatine kinase (CK), LDH and COR increased significantly (P<0.05) compared to the other conditions. The pork pH values 24 h after slaughter at the transportation temperature of -10?0℃ and 20?30℃ were significantly higher (P<0.05) than those at 0?10℃ and 10?20℃ which caused the pork quality to decrease. The research identified that the pigs in Beijing should be transported within 6 h and at 10?20℃ in order to reduce the impact of stress and improve pork quality.