一水肌酸调控运输应激肉仔鸡肌肉糖酵解代谢的机理研究

In modern poultry industry, market-age broilers are inevitably transported from farms to slaughterhouses before slaughter along with transport stress. Long-term transport has been reported to result in higher stress-induced death on arrival, live weight loss and even higher incidence of PSE-like meat, which causes substantial economic losses to the poultry industry. Our previous study showed that dietary supplementation with 1,200 mg/kg creatine monohydrate (CMH) for two weeks before slaughter decreased breast muscle glycolysis rate, and alleviated transport induced negative changes of breast meat quality by maintaining the higher muscle pH at 24 h postmortem and lower drip loss. On the basis of our previous research, centering on muscle glycolysis, this project intends to investigate the effect of dietary supplementation with CMH during the finishing period on muscle creatine absorption, contents of muscle creatine, phosphocreatine and adenosine phosphates, muscle glycolysis potential and activities of glycolytic key enzymes, to reveal the effect of CMH-induced energy buffering ability of creatine pool on glycolysis rate of long-term transported broilers. We further investigate the gene expression of glycogen phosphorylase (the key enzyme in glycogen breakdown) and glycogen synthase, as well as the key factors of LKB1/AMPK pathway, to unearth its regulatory mechanism of signal pathway. The results will provide new approaches for producing high quality chicken products, and finally provide a theoretical basis for developing CMH as an effective anti-stress additive in the management of transported broilers.

集约化养殖的肉鸡在集中送往屠宰厂的过程中不可避免会遭受运输应激。长途运输不仅使肉鸡的体重损失和死亡率增加，还会引起类PSE肉多发，给家禽屠宰业和肉品加工业带来巨大的经济损失。申请人前期研究发现，宰前两周日粮中添加1200 mg/kg一水肌酸（CMH）可降低3 h长途运输肉仔鸡胸肌的糖酵解潜力，提高宰后24 h胸肉的pH和系水力，改善肉品质。在前期研究基础上，本项目以肌肉糖酵解为研究靶点，通过分析骨骼肌肌酸吸收、磷酸肌酸合成与糖酵解潜力、糖酵解代谢关键酶活性变化的关系，明确肌酸代谢池的能量缓冲作用对运输应激肉仔鸡肌肉糖酵解速率的调节作用；深入研究糖原分解酶与合成酶基因表达及LKB1/AMPK信号通路关键因子表达的差异，阐明宰前补饲CMH调控运输应激肉仔鸡肌肉糖酵解代谢的信号因子表达机制。研究结果可为生产优质鸡肉产品的研究提供新思路，为开发缓解运输应激、改善宰后肉品质的有效添加剂提供理论依据。

集约化养殖的肉鸡在集中送往屠宰厂的过程中不可避免会遭受运输应激。长途运输不仅使肉鸡的体重损失和死亡率增加，还会引起宰后肌肉糖酵解速率加强、pH快速下降，造成类PSE肉多发，给家禽屠宰业和肉品加工业带来巨大的经济损失。通过宰前营养干预，增强肌细胞能量状态，降低肌肉糖酵解速率是潜在有效的调控手段。本项目以肉仔鸡为研究对象，探索日粮添加不同水平能量调节剂一水肌酸（CMH）对夏季长途运输肉仔鸡宰后肌肉糖酵解代谢和肉品质的影响，初步明确CMH的调控作用及剂量。在机理探讨方面，采用高效液相色谱、免疫组化、荧光定量PCR、western blot等方法研究了骨骼肌肌酸吸收转运、磷酸肌酸合成与糖酵解潜力、糖酵解代谢关键酶活性变化的关系规律，及LKB1/AMPK信号通路关键因子的调控机制。结果表明，（1）宰前2周日粮添加1200 mg/kg CMH可缓解肉仔鸡运输应激，减少体重损失，降低肌肉的糖酵解速率、改善宰后胸肉品质（提高pH和保水性），但运输应激和CMH添加对腿肌品质无显著影响；（2）日粮添加CMH可显著提高肉仔鸡胸肌中肌酸（Cr）和磷酸肌酸（PCr）水平，增强PCr/Cr能量缓冲体系作用，但CMH对肌肉自由基清除能力和抗氧化性能均无显著影响，由此可以确定日粮补充CMH主要通过降低肌肉的糖酵解速率改善宰后胸肉品质；（3）日粮中添加1200 mg/kg CMH显著上调胸肌肌酸转运载体表达，提高胸肌PCr/Cr系统的能量缓冲作用，改善肌肉能量状态，并通过抑制运输应激导致的LKB1/AMPK通路的激活降低肌肉糖酵解速率，进而改善宰后胸肉品质；（4）在此基础上，研究揭示了运输条件下肉仔鸡胸肌和腿肌的糖酵解代谢规律，及糖酵解关键酶与基因的调控机制。上述研究结果可为生产优质鸡肉产品的研究提供新思路，为开发缓解运输应激、改善宰后肉品质的有效添加剂提供理论依据。