基于“NMR代谢组学”的新产玉米诱导肉鸡肠毒综合征发病机制研究

Broiler intestinal toxicity syndrome (BITS) is a disease characterized by diarrhea, dehydration, undigested feeds accumulated in the intestinal canal，lower feed intake, poor growth, and died suddenly. This syndrome is prevalencing in recent years, and new harvested maize is one of the major cause. However, its mechanism of action is still on the exploratory stage. As a systematic biology research method, metabonomics studies the mechanism of new harvested maize on organisms from a holistic, dynamic point of view. Preliminary studies have shown that broilers’ performance is significant lower as the increasing of new harvested maize dose, and BITS is successful built as well. This study will use NMR-based metabonomics to conduct the following studies: to establish NMR spectroscopy of BITS caused by new harvested maize, to conduct qualitative and quantitative analysis on biological metabolites of new harvested maize, to screen the characteristic metabolites in model broilers' serum, liver, kidney, faeces and urine that can reflect the noxious effect, and analyze the effect of new harvested maize on these characteristic metabolites, to explore the metabonomic approach of new harvested maize on the model broilers, and finally, based on the above results, to explore the inducing mechanism of new harvested maize on the model broilers according to the theory of metabonomics and literatures so as to providing a new idea for researcher on mechanisms of BITS.

肉鸡肠毒综合征是一种以腹泻、脱水、肠腔中含有未消化的饲料、采食量下降、生长缓慢，以及突然猝死为主要特征的疾病，近年来呈流行上升趋势，新产玉米是主要的诱因之一，但对其诱病的作用机制的研究目前仍处于探索阶段。代谢组学技术是系统生物学的研究方法之一，它可以从整体的、动态的角度来研究新产玉米对机体的作用机制。前期研究证明，增加新产玉米添加量显著降低肉鸡生长性能，并成功构建肉鸡肠毒综合征动物模型。本研究将运用代谢组学技术进行以下研究：建立新产玉米诱导肉鸡肠毒综合征的核磁共振谱；对新产玉米的生物代谢产物进行定性定量分析，筛选模型肉鸡血清、肝脏、肾脏和粪尿液中能够反映其致病的特征代谢物，并分析新产玉米对这些特征代谢物的影响；绘制新产玉米诱导肉鸡肠毒综合征的代谢网络；最终，利用代谢组学的理论、参照文献探讨新产玉米诱导该病的作用机理，为该病的机制研究提供新的思路和参考。

肠毒综合征是夏秋季肉鸡常发的一种多病因综合征，以新玉米诱导的“过料”现象、生产性能低、肠黏膜炎症、肠壁脱落出血甚至坏死等较为普遍。本研究开展了“新产玉米对肉鸡生长性能和肠道微生物区系的影响”，“玉米不同贮藏期对肉鸡生长性能和养分利用的影响及其代谢组学解析”和“饲粮添加酶制剂对肉鸡生长性能和养分利用的影响及其代谢组学解析”等相关研究，结果表明：（1）饲粮添加60%新产玉米显著降低了肉仔鸡平均日增重，增加了肉仔鸡料重比(P<0.05)；与对照组相比，回肠属水平上60%新产玉米组（处理组）显著升高了Lactobacillus的相对丰度，降低Faecalibacterium的相对丰度(P<0.05)。盲肠属水平上处理组盲肠Lactobacillus、Faecalibacterium相对丰度显著高于对照组，Romboutsi相对丰度显著低于对照组(P<0.05)。（2）新玉米组（D0）肉鸡全期体增重显著低于18个月贮藏期玉米组（D18），且其料重比显著高于后者(P<0.05)；两组间NMR检测到39种差异代谢物（20种负离子代谢物和19种正离子代谢物），D0组8种离子显著低于D18组，而其L-蛋氨酸和L-同型胱氨酸显著低于D0组，而D18组胆固醇显著高于D0组(P<0.05)。通路分析发现原代胆汁酸生物合成和甾体激素生物合成在D0和D18之间受到影响。（3）饲养前期添加酶A（淀粉酶）或酶B（淀粉酶+木聚糖酶）均可改善饲喂新玉米饲粮肉鸡体增重和饲料转化率(P<0.05)；新产玉米饲粮添加酶制剂改变了血清代谢产物，酶A和CN、酶B和CN以及酶A和酶B组间分别发现150、64和35种不同代谢物；通路分析表明，酶A和CN对烟酸和烟酰胺、视黄醇、谷胱甘肽代谢途径有影响；酶B和CN对鞘脂代谢、卟啉和叶绿素代谢有影响。综上结果说明新产玉米对肉鸡生产性能和肠道微生物区系均有负面影响，添加淀粉酶和木聚糖酶是一种有效防治措施。