Myosin heavy chain composition in longissimus muscle of laiwu piqs and duroc

Chinese. 【目的】比较莱芜猪和杜洛克猪背最长肌肌球蛋白重链（MyHC）Ⅰ、Ⅱa、Ⅱx、Ⅱb的组成差异,探讨莱芜猪肉质优良的机理。【方法】选择体重100kg的莱芜猪10头和杜洛克猪7头,测定肉质性状,并用实时荧光定量RT-PCR方法检测背最长肌4种MyHC亚型mRNA的表达量,分析品种间差异。【结果】莱芜猪肌肉大理石纹评分和肌内脂肪含量显著高于杜洛克猪,肌肉失水率、剪切值和肌纤维直径显著低于杜洛克猪（P〈0.01）;莱芜猪背最长肌MyHCⅡa、ⅡxmRNA表达量显著高于杜洛克猪,MyHCⅡbmRNA表达量则显著低于杜洛克猪,而MyHCⅠmRNA表达量无明显变化。【结论】莱芜猪背最长肌氧化型肌纤维比例高于杜洛克猪,酵解型肌纤维比例低于杜洛克猪。表明莱芜猪背最长肌利用脂肪转化为能量的能力较高,即莱芜猪背最长肌氧化代谢功能高于杜洛克猪,这可能与其肌内脂肪含量较高、肉质细嫩多汁相关,这一结果可为通过肌纤维类型的选育提高肉品质的研究工作提供思路。

English. [Objective] An experiment was conducted to compare myosin heavy chains （MyHC） composition at mRNA in longissimus muscle （LM） between Laiwu pigs and Duroc, and to discuss the mechanism of high me,at quality in Laiwu pigs. [Method] Ten Laiwu pigs and seven Duroc weighing approximately 100 kg were chosen for the experiment. Meat characters were measured. Expression of MyHC Ⅰ, Ⅱ a, Ⅱx, Ⅱb at mRNA in LM of Laiwu pigs and Duroc were measured by real time fluorescence RT-PCR, the difference between breeds was analyzed. [Result] The result indicated that marbling grade and intramuscular fat content in LM of Laiwu pigs were remarkably higher than that of Duroc （P〈0.01）, water-losing percentage, shear value and fibre diameter in LM were evidently slower than that of Duroc （P〈 0.01）. Compared with Duroc, the expression level of MyHC Ⅱ a, Ⅱ x at mRNA in LM of Laiwu pigs significantly increased, expression level of MyHC IIb at mRNA dramatically decreased, but expression level of MyHC I at mRNA were not influenced by breeds. [ Conclusion ] The proportion of oxidative fiber in LM of Laiwu pigs was higher than that of Duroc, but the proportion of glycolytic fiber was lower, which suggested that LM of Laiwu pigs exhibited a less glycolytic and more oxidative metabolism than Duroc＇s, potentially using more lipids as an energetic substrate, consisting with higher intramuscular fat content, tenderness, water-holding capability. In the future, meat quality can be improved by selecting muscular fibctypes.