肠道微生物宏基因组影响猪饲料转化率的分子机理

Feed consumption occupies about 60%-80% of pig production cost.So it is extremely important to improve the feed conversion ratio for reducing the production cost.Many factors can affect the feed conversion ratio,including genetics, enviroment and health status of pig population. There have been some studies in humans confirming that gut microbiota affect the metabolism of food and absorbing of nutrition,and related to many metabolic diseases. In this project, we will use Duroc as the experimental material.The feed conversion ratio for all experimental pigs will be measured by electronic automatic feeder. And then, we will initially isolate the gut microbiota that are significantly associated with feed conversion ratio in 160 experimental pigs by 16S rRNA sequencing.After that, total 20 individuals which showed extreme difference in feed conversion ratio and structure of gut microbiota will be chosen to perform the metagenome sequencing analysis.Based on the metagenomic sequencing analysis, we will perform a metagenome-wide association study of gut microbiota in feed conversion ratio to identify metagenomic markers associated with feed conversion ratio.The expression profiles of these associated metagenomic gene markers will be tested in porcine gut. And the molecular mechanisms about effects of metagenome in feed conversion ration will be illustrated by using these data. Based on above results, we will explore whether metagenomic predictions can be used to predict the feed conversion ratio of breeding herds. The studies of this project will provide the important guides on improving the feed conversion ratio through artificially adjusting the gut microbiota.

养猪生产中，60%～80%的生产成本来自于饲料，提高猪饲料转化率对降低饲养成本极为重要。饲料转化率受遗传、环境条件和猪群健康状况等很多因素影响，在人类中已有研究表明，肠道微生物影响食物消化吸收，和许多代谢疾病密切相关。因此本研究将利用纯种杜洛克为研究材料，采用电子自动喂料器测定实验猪群的饲料转化率，对160个个体进行16S rRNA测序，初步分离与饲料转化率相关的肠道微生物种类，在此基础上选择饲料转化率和肠道菌群都差异极端的个体20头进行肠道微生物宏基因组测序，通过宏基因组基础上的关联性分析分离与饲料转化率显著相关的宏基因组标记，并分析这些宏基组基因标记在猪肠道中的表达情况，阐明宏基因组影响猪饲料转化率的分子机制。据此探讨利用宏基因组预测( Metagenomic prediction)来进行提高饲料转化率的种猪选择的准确性。本项目研究为通过肠道微生物调控提高猪饲料转化率奠定理论基础。

畜牧业每年消耗的饲料粮接近粮食总产量的40％，我国养猪业的料肉比每降低0.1，每年可以节约饲料721万吨。越来越多的研究表明肠道菌群是影响猪饲料转化率的重要因素之一。本研究使用电子喂料器测定了280头杜洛克猪的饲料转化率（RFI）和平均日采食量（ADFI），在140日龄时从肛门收集所有280头猪粪便样品。课题组测定了高、低饲料转化效率各10头猪的粪便中短链脂肪酸含量，比较了两者在短链脂肪酸组成和含量上的差异。所有粪便样品进行了16S rRNA基因V4区测序。课题组首先评估了肠型和猪饲料转化率之间的关系，发现和Prevotella肠型猪相比，Treponema肠型猪具有更高的饲料转化率。采用two-part模型，共检测到31个OTU与RFI相关，其中注释到Christensenellaceae、Ruminococcaceae、Lachnospiraceae、Bacteroidales的OTU提高猪饲料利用率，而注释到Prevotella、Faecalibacterium prausnitzii的OTU降低饲料利用率。课题组选择20头饲料转化率表型极端个体（高、低各10头）的粪便DNA进行宏基因组测序，在P < 0.05时，共发现36种细菌与猪RFI相关，包括Desulfovibrio desulfuricans和Lactobacillus casei等在饲料转化率高的猪肠道中富集。共发现29个KEGG同源基因（KO）与猪RFI显著相关，其中与单糖代谢和转运、信号转导相关的KO在饲料转化率低的猪中富集，而氮代谢、氨基酸代谢和转运系统等相关KO在饲养效率高的猪中富集。在此基础上，课题组利用宏基因组测序数据，建立了利用饲料转化率相关的KO预测猪饲料转化率的方法。课题组还分析了肠道微生物组对猪ADFI的影响，发现Prevotella肠型猪具有更高的ADFI。分析发现Prevotella（特别是Prevotella copri）显著提高猪平均日采食量，且是提高猪采食量的核心菌；而Ruminococcaceae和Lactobacillus等产短链脂肪酸和乳酸的菌显著降低猪采食量。肠道菌群宏基因组功能分析发现，氨基酸合成和代谢相关的基因与猪ADFI显著相关。课题相关研究结果为通过调控肠道菌群来提高猪饲料利用率和调节采食量提供参考数据，为提高猪饲料利用率的微生态制剂开发提供理论基础。