Effect Of Halothane Genotype On Expression Of MyHC And Energy Metabolism In Longissimus Dorsi Muscle Associated With Pork Quality

In this study, pigs at 65 kg of body weight differing in halothane genotype (Hal^NN, homozygous wild type; Hal^Nn,heterozygous; Halⁿⁿ,homozygous mutant) were employed to investigate the influence of halothane genotype on myofiber type composition and muscle energy metabolism, in association with meat quality.1.Comparison of meat quality traits among different halothane genotypes of pigsMeat quality indice including pH_45min,pH_24h,water holding capacity (WHC), meat color,W-B shear force of longissimus dorsi were measured.pH_45min in Halⁿⁿ wassignificantly lower than Hal^NN (P < 0.01), and there was no significant difference between Hal^NN and Hal^Nn.pH_24h Halⁿⁿ dropped under 6.0, and significantly lower than that of Hal^Nn (P<0.05). Meat color analysis revealed that L* and b* values in Halⁿⁿ were both significantly higher than in Hal^Nn (both P<0.05), and no significant difference between Hal^NN and Hal^Nn was observed. W-B shear force values were similar between different halothane genotypes. Results indicated that Hal^NN pigs exhibited the best pork quality, Haⁿⁿ showed a slight PSE syndrome, and Hal^Nn were the intermediate.2.Comparison of muscle myofiber type composition among different halothane genotypes of pigsMultiplex-PCR established by Tanabe et al (1999) was introduced to analyze the composition of contractile myofiber type in longissimus dorsi among different halothane genetypes of pigs. Results indicated that there were no significant genotype differences in the percentages of MyHCâ… andâ…¡a isoforms, but Halⁿⁿ showing significantly higherâ…¡a and lowerâ…¡x,compared with Hal^NN and Hal^Nn (both P<0.05).3.Comparison of energy metabolic indice and expression of metabolic enzymes and glucose transport related genes among different halothane genotypes of pigsSerum glucose concentraton in Hal^NN and Hal^Nn was significantly lower than that in Halⁿⁿ (P<0.05), while there was no significant difference between Hal^NN and Hal^Nn.Serum LDH activity in Hal^NN was significantly lower than that in Hal^Nn and Halⁿⁿ (P<0.05). There was no significant genotype difference in serum CK activity.Halⁿⁿ demonstrated significantly higher glycogen and LD contents in longissimus dorsi compared with Hal^NN and Hal^Nn (both P < 0.05), while no difference was observed between Hal^NN and Hal^Nn.Besides, there were significantly lower CK and LDH, higher AMPK activities in longissimus dorsi of Halⁿⁿ than those in Hal^NNand Hal^Nn (all P<0.05). Real-time PCR results showed that GLUT4 and PGC-1αtranscripts were significantly higher in Hal^NN compared with Halⁿⁿ, and no significent difference between Hal^Nn and Halⁿⁿ was observed. These results indicate that longissimus dorsi muscles from different halothane genotype exhibit distinct metabolic patterns.Taken together, the effect of halothane genotype on longissimus dorsi muscle of pigs at 65 kg body weight was dramatically significent, indicated by meat quality traits (pH values, WHC and meat color, et al),metabolic indice, as well as pattern of gene expression. Hal^NN pigs possess super pork quality, while Halⁿⁿ exhibited mild PSE syndrome. Halⁿⁿ had the highest proportion ofâ…¡b MyHC.Different metabolic pattern and MyHC might contribute to the formation of undesirable meat quality in Halⁿⁿ.Besides, Halⁿⁿ also exhibited significantly lower CK and LDH, higher AMPK activity as well as lower expression of GLUT4 and PGC-1αmRNA in the muscle. These results indicate that Hal^NN pigs have much higher capacity of energy metabolism both in aerobic metabolism and anaerobic glycolysis which may contribute to the better meat quality.