Effects of castration time on meat quality of Congjiang Xiang pig

【Objective】To analyze effects ofdifferent castration time on meat quality of Congjiang Xiang pigs and to provide reference fordetermining optimal castration time of Congjiang Xiang pigs.【Method】12 male Congjiang Xiang pigs of 20d were selected to form a 25d-castrated group(C_25d group),120d-castrated group(C_120d group),180d-castrated group(C_180d group) and uncastrated group(UC group). They were fed and managed uniformly until they were slaughtered at 240d. Based on meat quality traits measured according to Technical Regulation for Determination of Pork Quality(NY/T 821—2004),a meat quality comprehensive scoring model was constructed by principal component analysis. ELISA and real-time fluorescence quantitative PCR(qRT-PCR) were used todetect the content of taint substances in the pigs and expression of genes involved in metabolic taint substances.【Result】Muscle pH_{24 h} of C_25d group was significantly higher than that of C_120d group(P<0.05,the same below) ;in terms of meat color score,the scores of UC group and C_25d group were significantly higher than those of C_180d group and C_120d group;unlike situation of meat color,shear force and intramuscular fat content of C_180d group and C_120d group were significantly higher than those of UC group and C_25dgroup;intramuscular moisture content followed an order of C_25d group > UC group > C_180d group > C_120d group;intramuscular protein content of C_120dgroup was significantly higher than that of C_180d group,C_25d group and UC group. The comprehensive scoring model of meat quality traits was established through principal component analysis(PCA). Three principal components(cumulative contribution rate of 100.00%) were extracted from 10 meat quality indexes,the first principal component included meat color,shear force,intramuscular moisture and intramuscular fat content,the second principal component included pH_{24 h},marbling anddrip loss,and the third principal component included pH_{45 min},cooked meat rate and intramuscular protein content. The comprehensive score of meat quality of Congjiang Xiang boars was in the order of C_25d group >UC group > C_180d group > C_120d group. Castration time had no significant effect on androsterone content in liver and fat,and skatole content in fat,longissimusdorsi muscle and liver(P>0.05,the same below);androsterone content in longissimusdorsi muscle of C_25d group was significantly lower than that of C_120d group and UC group. CYP2E1 gene,the key enzyme of skatole metabolism,was expressed in liver of Congjiang Xiang boars in C_120d group,C_180d group and UC group,and no significantdifference between groups wasdetected.【Conclusion】Castration time influences meat color,shear force,intramuscular fat,intramuscular moisture and intramuscular protein of Congjiang Xiang boars. Meat quality of Congjiang Xiang boars castrated at 25d is better,and if the time is missing,no castration is recommended given animal welfare.