Effect Of Heat Stress On Redox Balance And Meat Quality Of Growing Pigs

In order to evaluate the sensitivity parameters to heat exposure, three experiments were conducted to investigate the effect of acute and chronic heat stress on redox balance and concentration of lactic acid of plasma and the alterations of meat qulity of pigs due to heat stress. In Exp1, Twelve pigs were used to determine the alterations of peroxidation and lactic acid in plasma of growing pigs under acute heat stress (40℃,3h). The result showed that these were obvious rhythm in plasma malondialdehyde (MDA), the superoxide dismutase (SOD) and T-AOC were obvious. The plasma SOD activity and MDA concentrations were increased significantly by acute heat stress (P﹤0.05). After the high temperature was removed, the SOD activity and MDA level in plasma restored to normal levels. The MDA level in plasma had obvious difference among individuals. And the plasma MDA level had a obviously reverse dependence relation with the T-AOC. All these results the peroxidation was induced by acute heat stress.But the lactic acid (LD) content in plasma was significantly affected by acute heat stress(P﹤0.05). In Exp2, ten pigs were used to estimate the effect of chronic heat stress on peroxidation and lactic acid of plasma. The temperature of contral group was 18℃ to 23℃, and treatment group was from 30℃ to 38℃. The experiment lasted fourteen days. The blood plasma samples were taken and examined at day 0, 1, 2, 4, 3宋伟:温热环境对生长猪过氧化反应及肉品质的影响7, 10, 14. The results showed that: At first, the activity of SOD and T-AOC in plasma was increased significantly to 2 days by thermal environmeat in the experment(P﹤0.05);with the days went,they began to decrease. The plasma MDA content increased significantly to the forth day of stress. The SOD activity and T-AOC were decreased by chronic heat stress of fourteen days. The plasma T-AOC had obviously reverse dependence relation with the MDA on the first day .After two days, the SOD had obviously reverse dependence relation with the MDA. Compared to controling group, the plasma lactic acid conten was not significantly changed(P﹥0.05). The Exp3, ten pigs were sacrificed after achieving the second experment to determine meat quality. The result indicated that: The pigs of treatment group had higher meat color A* value, and lower L* value, B* value. Water holding capacity, shear value of pork were decreased, and total cholesterol(CH) value,ether extracts, NEFA (P﹤0.05) were increased by heat stress. The alterations of sarcous pH value, IMP, crude proteinof pork was not significant (P﹥0.05). Compared to control group, thermal environment notable effected muscle glycogen(MC), LDH, phosphorus and LD content (P﹤0.05). The concentrations of SOD, MDA in sarcous were not effected by heat stress(P﹥0.05); and the activities of T-AOC in sarcous was improved notably (P﹤0.05). In histology, muscle cells were destructed severely. The last, the first principal component was determined by the AST, ALT, LDH, CK in plasma;the second principal component was determined by SOD and T-AOC. The plasma LDH may reflect the changes of the T-AOC in muscle.