低聚糖降低肉仔鸡粪臭素产生的微生物学机制研究

Skatole(3-methylindole) produced by the microbial degradation of L-tryptophan mainly in the hindgut of broiler chickens，is considered to be the main contributor to chicken feces malodorous. It has been confirmed that the amount and source of oligosaccharides in the diet can altered the pattern of intestinal microbial substrate use and have an effect on skatole production, but the exact mechanism is not clear, and systematical investigations on various microbiota participating in skatole formation in broiler chickens are little. In this experiment, by the method of combination of in vitro and in vivo research approaches with molecular ecology and metaproteomics techniques, the basic rules of skatole formation and microbial composition in different segments of intestine in broilers will be researched in order to ascertain the microbiology foundation on intestinal skatole production. Then the effects of broiler chickens caecum bacteria and fecal bacteria on fermentation of different oligosaccharides will be investigated,and the dynamic changes of metabolites, related microflora and microbial proteome will be analyzed, to explore the possible microbiological mechanisms of skatole formation affected by oligosaccharide in broiler chickens. There after, the effect of oligosaccharide on skatole production and intestinal microecology in broiler chickens will be further evaluated by animal experiment, feeding diets supplemented with different levels oligosaccharide which was significantly effective in reducing skatole formation,and the microbiological mechanisms of skatole reduction affected by oligosaccharide in broiler chickens will be revealed. That will provide theoretical basis for developing micro-ecological preparations and decreasing skatole pollution in raising chickens, and have a great scientific significance on probing low carbon animal production way.

粪臭素（3-甲基吲哚）是肉仔鸡后肠微生物降解L-色氨酸的主要代谢产物，是引起鸡粪恶臭的主要物质。研究表明，适量低聚糖来源可改变肠道微生物发酵模式降低粪臭素产生，但其作用机理还不完全清楚，系统地对参与粪臭素产生的各种菌群的定性、定量研究也不多。本项目拟采用体外发酵技术、动物试验，结合分子生态学和宏蛋白质组学技术，首先通过研究肉仔鸡粪臭素产生基本规律和肠道微生物区系组成，探明与粪臭素生成相关的微生物学基础；然后通过研究肉仔鸡盲肠、直肠菌群对低聚糖的发酵作用，分析代谢产物、相关菌群及蛋白质组的动态变化，探索低聚糖影响肉仔鸡粪臭素产生的可能微生物学机制；最后选择对粪臭素产生有显著降低作用的低聚糖进行动物试验进一步探讨对肉仔鸡粪臭素产生的调控作用和肠道微生态的影响，揭示低聚糖降低粪臭素产生的微生物学机制。为开发相关微生态制剂和降低养鸡业粪臭素污染提供理论指导，对探索低碳畜牧生产方式具有重要科学意义。

粪臭素是微生物降解L-色氨酸（L-try）的代谢产物，是引起鸡排泄物产生恶臭的主要物质。本项目通过肉仔鸡体内外试验，采用PCR-DGGE、qPCR及蛋白组学技术，在研究肉仔鸡粪臭素产生基本规律的基础上，探讨了低聚糖种类、水平及组分对粪臭素产量及肠道菌群的影响，揭示了低聚糖降低肉仔鸡粪臭素产生的微生物学机制。试验分五部分：1）粪臭素产生的基本规律及与肠道微生物组成的变化关系：测定了肉仔鸡粪臭素产生的时空变化规律，并结合肠道微生物组成探讨了与粪臭素生成相关的微生物学信息。表明粪臭素产量随周龄增长而增加；粪臭素主要在盲肠产生，与菌群多样性，总菌、乳酸菌和双歧杆菌数量具有显著正相关关系；2）四种功能性低聚糖对肉仔鸡排泄物粪臭素产量及盲肠菌群组成的影响：表明，饲粮添加1.25 g/kg大豆低聚糖（SBO），显著提高了肉仔鸡盲肠菌群多样性，降低了排泄物主要臭气化合物浓度，并推测Uncultured Lachnospiraceae bacterium and Bacteroides sp.与粪臭素产生有关；3）菊糖和SBO对体外条件下肉仔鸡肠道粪臭素产量及菌群组成的影响：表明盲肠发酵液添加菊糖或SBO，可通过改变菌群组成、数量及微生物蛋白表达，显著降低粪臭素产量和L-try降解率，菊糖的降低效果优于SBO，并提示uncultured Bacteroides uniformis (T) and Enterobacter aerogenes与L-try的降解有关；4）菊糖水平对肉仔鸡粪臭素产量及肠道菌群的影响：表明添加菊糖降低了肉仔鸡粪臭素水平，显著影响盲肠和直肠菌群结构和主要菌群数量，最适菊糖添加水平为2.5～5 g/kg；5）SBO及功能组分对体外条件下肉仔鸡盲肠粪臭素产量及菌群组成的影响。表明添加1%的SBO、蔗糖和水苏糖显著降低了发酵液粪臭素浓度，降低幅度分别为79.04%、71.88%和70.28%。显著提高发酵液菌群丰富度。SBO及其功能组分促进了Blautia producta、Parabacteroides distasonis、Lactobacillus reuteri的增值。综上，低聚糖尤其SBO，可通过改变肉仔鸡盲肠微生物菌群组成、蛋白质表达水平和发酵环境，降低粪臭素产量。此结果为相关微生微生态制剂研发、低聚糖有效利用及减少养鸡业环境污染提供了理论与实践依据。