Effect Of Transport Stress On The Muscle Fibres Characteristics Of Different Halonthane Genotypes Pig

The objective of this study was to compare the influence of transport stress on myofibre properties using histological and histochemistry methods as well as electron microscopy technology among three different halothane(Hal) genotypes of F2 offspring pig of Erhualian and Pietrain parents.The Erhualian pigs are the most prolific pig in the world,have well-disposed,and exhibit lower growth rate,poorer feed efficiency and lower lean meat content than conventional Western pig breeds,but superior sensory quality of meat and stress-resistant.Pietrain pigs have a well lean percentage in the carcass and lean-to-bone ratio,but stress-susceptible which is prone to product poor meat.Therefore,this study was designed to investigate postmortem size and distribution of semitendinosus,longissimus dorsi(LD) and psoas muscle fibre types,and the differences of sarcomere length,glycogen content,lactate dehydrogenase(LDH) activity,succinate dehydrogenase(SDH) activity and meat quality characteristics responce to transport.The whole experiment can be divided into three parts:1.Compare of muscle fibre types in Hal^NN,Hal^Nn and Halⁿⁿ pigsMuscle fibre in semitendinosus,longissimus dorsi(LD) and psoas muscle were differentiated by the method of Brooke and Kaiser(1970),which uses the histochemical reactions ATPase,the reaction is highly sensitive for changes in pH and is finely adjusted to allow for clear discrimination between three fibre types:typeâ… , typeâ…¡a and typeâ…¡b.The results indicated that no significant difference were found in each type myofibre area,collagen fiber-to muscle bundle ratio,rigor mortis degree after 24h of three muscles among Hal^NN,Hal^Nn.Halⁿⁿ pigs.It demonstrated that no significant difference might be attributed to the same genetic background.2.Effect of transport stress on the myofibre characteristics in Hal^NN,Hal^Nn and Halⁿⁿ pigsThe glycogen content,lactate dehydrogenase and succinic dehydrogenase activities in semitendinosus,LD and psoas muscles were using histochemistry method for estimating the muscle energy metabolism capacity.The results indicated that:(1) The glycogen content and LDH activity of all the three muscles in Hal^an pig were significantly higher than that in Hal^NN pig at 45 min(P＜0.01),what in Hal^Nn pig were also significantly higher than in Hal^NN pig(P＜0.05),but no significant difference were found between Halⁿⁿ and Hal^Nn pigs.(2) The glycogen content of all the three muscles in three halothane genotypes pig were almost exhausted after 24h,and the LDH activity of all the three muscles in experiment pig were significantly decreased and lower than the correspondence at 45 min(P＜0.01).(3) The SDH activity of all the three muscles in Hal^NN pig were significantly higher than that in Halⁿⁿ pig at 45 min (P＜0.01),what in Hal^NN pig were also significantly higher than in Hal^Nn pig(P＜0.05), but no significant difference were found between Halⁿⁿ and Hal^Nn pigs.(4) The SDH activity of all the three muscles in experiment pig were significantly decreased and lower than the correspondence at 45 min(P＜0.01).These results demonstrated that the capacity of anoxic metabolism of muscle in Halⁿⁿ pig is larger than that in Hal^NN pig,it showed this halothane genotype pig is sensitive to stress;the capacity of aerobic metabolism of muscle in Halⁿⁿ pig is weaker than that in Hal^NN pig,it showed Hal^NN pig is relatively insensitivity to stress,so different halothane genotypes pig exhibit different meat quality characteristics after mortem.3.Effect of transport stress on the ultrastructure of myofibres in Hal^NN and Halⁿⁿ pigsUsing transmission electron microscopy,we observed the ultrastructure of LD muscle.Observation found that the ultrastructure of LD muscle in Hal^NN pigs was morphologically clear and integrity.But the muscle in Halⁿⁿ pigs was severely contracted,some sarcomeres had super-contraction band;the myofilaments were deranged and not clear,some myofibrils were even degradated;Z line were arranged irregularly;the mitochondria were swelled or degradated and the sarcoplasmic reticulum were not obvious.The length of sarcomares and I-bands were measured on the micrographs of longitudinal sections.The statistic results suggest the sarcomere and I-bands length in Halⁿⁿ pig was significantly shorter than that in Hal^NN pig(P＜0.05).These results demonstrated that different halothane genotypes pig exhibited different muscle contraction characteristics,Hal^NN pig contracted muscle lightly,Halⁿⁿ pig contracted muscle intensely.It was presumed that this correlated with meat tenderness and water holding capacity of different stress sensitivities pig after mortem.