陳 鵬，丁武億

（ 1.北京英惠爾生物技術(shù)有限公司，北京 100081；2.贛州市畜牧研究所，江西 贛州 341000）

豬腸道菌群特點(diǎn)和生長(zhǎng)的關(guān)系

陳 鵬1，丁武億2

（ 1.北京英惠爾生物技術(shù)有限公司，北京 100081；2.贛州市畜牧研究所，江西 贛州 341000）

豬腸道定植的菌群不僅對(duì)豬的整體健康有影響，還對(duì)其營(yíng)養(yǎng)，生產(chǎn)性能和肉質(zhì)至關(guān)重要。許多因素會(huì)影響腸道菌群的多樣性和活性，包括豬的日齡、生長(zhǎng)環(huán)境、抗菌劑、日糧組成、添加劑、飼料加工、疾病、斷奶、季節(jié)、應(yīng)激和基因。這些因素還能互相作用，讓腸道菌群的研究變得困難。腸道菌群的特征是近幾年的研究熱點(diǎn)領(lǐng)域，尤其是高通量測(cè)序方法的使用使得研究越來越深入。文章綜述了豬腸道微生物菌群的研究進(jìn)展，重點(diǎn)闡述了仔豬斷奶期腸道菌群的變化，豬生長(zhǎng)性能和腸道菌群潛在的關(guān)系。

豬；腸道菌群；生長(zhǎng)

哺乳動(dòng)物的腸道菌群對(duì)其宿主有很多的貢獻(xiàn)，比如其可以對(duì)碳水化合物進(jìn)行消化和發(fā)酵，生產(chǎn)維生素，維持腸道絨毛的正常功能，調(diào)節(jié)免疫應(yīng)答和預(yù)防病原性細(xì)菌的侵害[1-6]。最近幾年，豬腸道菌群成為了研究熱點(diǎn)，畜牧領(lǐng)域的關(guān)注度也很高[7-9]。

本文主要就仔豬斷奶期腸道菌群的變化，豬生長(zhǎng)性能和腸道菌群潛在的關(guān)系作以綜述，為完善豬日糧配方，減少抗生素的使用，平衡腸道菌落和提高豬腸道健康提供參考。

1 斷奶期腸道菌落的變化

仔豬出生時(shí)，腸道菌群開始定植，主要通過采食母奶塑造菌群結(jié)構(gòu)，形成母乳導(dǎo)向型菌群型，因?yàn)槟改讨械亩嗵遣荒鼙蛔胸i利用，只能被特定微生物利用，從而促進(jìn)了某些菌群生長(zhǎng)，比如乳酸菌群成長(zhǎng)的營(yíng)養(yǎng)物質(zhì)優(yōu)勢(shì)[6]。在哺乳階段，窩仔豬和母豬一起讓仔豬糞便的菌群繼續(xù)分化，如果存在寄養(yǎng)母豬哺乳，那么腸道菌群的發(fā)育會(huì)受到顯著的影響。因此，哺乳階段是仔豬腸道菌群進(jìn)行修飾的一個(gè)特有窗口期[10-12]。

仔豬出生時(shí)接觸到的各種各樣的微生物主要來源于母豬腸道和周圍的環(huán)境，腸道菌群開始建立。另外，新生仔豬在斷奶前不斷和母豬糞便，皮膚和黏膜上皮接觸。豬腸道菌群的建立和分化是和日齡相關(guān)。

哺乳仔豬的菌群主要是Bacteroides，Oscilli?bacter，Escherichia/Shigella，Lactobacillus和未分類的Ruminococcaceae屬，這和斷奶后仔豬腸道菌群構(gòu)成相反，主要是Acetivibrio，Dialister，Oribacteri?um，Succinivibrio和Prevotella屬。Lactobacillus fermen?tum可能由母乳或者糞便垂直傳播。仔豬斷奶后腸道菌群和其宿主共同進(jìn)化成兩種不同的群，主要由未被分類的Ruminococcaceae和Prevotella區(qū)別。Pre?votella和腔分泌IgA水平與體重正相關(guān)[13-16]。

盡管現(xiàn)代日糧配方更重視氨基酸平衡，但是斷奶時(shí)，仔豬要采食含有谷物和相對(duì)高比例的蛋白質(zhì)日糧。另外，給哺乳仔豬設(shè)計(jì)的開口料應(yīng)以減少斷奶時(shí)食物環(huán)境的突然變化為目的。在斷奶過渡期很多研究表明，Lactobacillus菌群數(shù)量下降，菌群多樣性減少，而Clostridium spp，Prevotella spp或者兼性厭氧菌Proteobacteriaceae，包括E.coli增多。蛋白質(zhì)或者纖維原料的來源和添加水平塑造了斷奶仔豬腸道菌群的多樣性和結(jié)構(gòu)[17-18]。比如，角質(zhì)含量高的豆粕日糧可以減低Lactobacillus的相對(duì)豐度，增加結(jié)腸中Prevotella的豐度，魚粉源飼料增加了Escherichia/Shigella比例[19]。

在所有被斷奶過渡所影響的生理和腸道要素中，腸道菌群紊亂很可能是導(dǎo)致仔豬斷奶后腹瀉的首要因素之一。因此，仔豬斷奶過渡時(shí)伴隨著的菌群狀態(tài)的打亂，被稱作“失調(diào)”。盡管失調(diào)在哺乳動(dòng)物中被定義為腸道菌群的失衡，專性厭氧菌，比如Clostridia和Bacteroidia類顯著減少，兼性厭氧菌，比如Enterobacteriaceae相對(duì)豐度增加，但是這種現(xiàn)象的特點(diǎn)還沒有完全研究清楚。早期腸道菌群生物系統(tǒng)的紊亂和菌群多樣性的消失能很大程度地提高消化道疾病發(fā)生的風(fēng)險(xiǎn)。尤其像Lactobacillus spp是預(yù)防疾病的主要菌群，斷奶期間突然的減少會(huì)導(dǎo)致疾病風(fēng)險(xiǎn)增加[20-21]。飼料中添加抗生素也可以導(dǎo)致斷奶仔豬腸道菌群失衡，抗生素具有廣泛的殺菌活性，因此對(duì)有害病原菌和有益菌都有殺死或抑制其生長(zhǎng)的作用，從而使菌群的多樣性進(jìn)一步降低[22-24]。長(zhǎng)期預(yù)防性劑量和治療性使用抗生素能夠增加病原性微生物的增殖和引起疾病[25]。Salmonella entericaserovar Typhimurium（S.Typhimurium）和E.coli是影響?zhàn)B豬業(yè)的兩大主要病原菌。E.coli中，enterotoxigenic E.coli（ETEC）是主要的仔豬斷奶后腹瀉傳染體，每年世界范圍50%的仔豬死亡都是由其引起的[25-30]。

2 腸道菌群特點(diǎn)和豬生長(zhǎng)性能的關(guān)系

豬腸道菌群用門水平分類主要有3種，F(xiàn)irmicutes，Bacteroidetes和Proteobacteria，豬腸道不同位置的菌群不同[1-3]。在門水平上，結(jié)腸和盲腸的菌群組成主要是Firmicutes或Bacteroidetes，這兩種菌占總檢測(cè)菌>90%。然而，空腸和回腸菌群的組成完全不同，在空腸中，F(xiàn)irmicutes是最優(yōu)勢(shì)菌，占90%以上，其次是Proteobacteria，Cyanobacteria和Actinobacteria。回腸中Firmicutes and Proteobacteria是主要的優(yōu)勢(shì)菌，然后是Proteobacteria，Cyanobac?teria和Actinobacteria。在回腸中Firmicutes和Proteo?bacteria是主要的優(yōu)勢(shì)菌，Proteobacteria占比在5%~40%之間。腸道的取樣位置對(duì)豬腸道菌群的組成和結(jié)構(gòu)有較大的影響。技術(shù)誤差，尤其是測(cè)序16S rRNA基因超變量的位置，也顯著影響豬腸道菌群的組成。盡管存有這些差異，但也發(fā)現(xiàn)大量相同點(diǎn)，所有收集的糞便樣品中有99%含有Prevotella，Clostridium，Alloprevotella 和 Ruminococcus。另外，90%的腸道樣品中含有Clostridium，Blautia，Lacto?bacillus，Prevotella，Ruminococcus，Roseburia 和 Sub?doligranulum[31-40]。

豬腸道菌群是一個(gè)非常復(fù)雜的生理系統(tǒng)，在腸道中隨著時(shí)間呈現(xiàn)動(dòng)態(tài)的結(jié)構(gòu)和多樣性[14]。腸道菌群的差異性能夠解釋豬體重的變異，例如，在門水平上，F(xiàn)irmicutes和Planctomycetes在體重大的豬腸道的相對(duì)豐度更大，而Bacteroidetes在體重小的豬上更豐富[9]。同時(shí)在種水平上，也發(fā)現(xiàn)了體重和菌群的相關(guān)性。Prevotella和體重成正相關(guān)[10]。腸道菌群組成在瘦和肥胖豬之間也有差異，肥胖豬腸道Firmicutes增加[6]。另外，體重大和生長(zhǎng)速度快的豬腸道菌群多樣性更高[1,9]。豬對(duì)飼料的利用效率和和腸道菌群也存在關(guān)系，飼料利用效率高的豬的盲腸的Lactobacillus更豐富。飼料效率高的豬盲腸中總揮發(fā)性脂肪酸和結(jié)腸中丁酸的水平也更高，也可由菌群組成和功能的差異解釋[11]。研究表明，在飼料中長(zhǎng)期低劑量添加抗生素，菌型分析發(fā)現(xiàn)，豬中Proteo-bacteria（1%~11%）的豐度增加，宏基因組分析表明，和能量生產(chǎn)轉(zhuǎn)化的菌落功能基因增加[22]。有差別的菌不是很常見，抗生素增加了Deino?coccus-Thermus phylum豐度，其和抵抗環(huán)境應(yīng)激有關(guān)，僅在人類腸道中發(fā)現(xiàn)；另外，Ruminococcus spp是反芻動(dòng)物和豬消化道常見的菌，使用抗生素后使其豐度增加可能提高豬的飼料轉(zhuǎn)化率。

Ramayo等首次從整體的角度研究豬腸道菌群，發(fā)現(xiàn)菌群生態(tài)系統(tǒng)和豬生長(zhǎng)性狀有關(guān)聯(lián)，并預(yù)見未來豬腸道菌型概念可能對(duì)畜牧生產(chǎn)業(yè)發(fā)揮重要作用[1]。仔豬腸道樣本可以分為兩種菌型，分別是優(yōu)勢(shì)菌Ruminococcus和Treponema，視為PEA型，或者是優(yōu)勢(shì)菌Prevotella和Mitsuokella，視為PEB型。菌型對(duì)斷奶仔豬的體重和日增重的影響顯著，與PEA型豬相比，PEB型豬的體重和日增重分別提高了850和17.9 g。結(jié)果表明，斷奶后仔豬生長(zhǎng)速度的差異部分是由腸道菌群生態(tài)系統(tǒng)差異驅(qū)動(dòng)的。PEA型主要參與丁酸、氮和氨基酸（例如丙氨酸、天冬氨酸或谷氨酸）代謝。PEB型主要參與碳水化合物代謝。因此，PEB型仔豬可能更適應(yīng)含有植物性多糖生長(zhǎng)豬的日糧，因?yàn)橛蒔revotella產(chǎn)生了大量的短鏈揮發(fā)性脂肪酸，解釋了與PEA型豬相比，其體重和日增重更大。另外，PEB型豬的碳水化合物活性酶的活性顯著性高。這些都表明PEB型豬有更強(qiáng)的消化含有谷物的常規(guī)日糧的能力。在豬整個(gè)生命周期中和飼料效率相關(guān)的腸道菌群組成，主要是在育肥期腸道菌群和飼料效率有可能相關(guān)聯(lián)[13]。具體表現(xiàn)為有益菌群，比如Clostridiale?sand Bacteroidetes的豐度越高，有害菌群比如Rho?dococcusand Erysipelotrichaceae的豐度越低，其豬的飼料效率越高。但是，很多和飼料效率相關(guān)的菌群組成差異相對(duì)不明顯，出現(xiàn)在相對(duì)豐度小的分類群上。

揭示飼料效率高的豬腸道菌群特點(diǎn)有助于定義提高飼料效率的最佳腸道菌群構(gòu)成。菌群結(jié)構(gòu)的變化和飼料效率相關(guān)聯(lián)，表明通過修飾腸道菌群的組成可以改善飼料效率的可能性。尤其是豬腸道菌群內(nèi)部已被證明具有有益功能的特定細(xì)菌，可以作為確定未來有可能的飼料效率指標(biāo)的生物學(xué)標(biāo)記。優(yōu)化腸道菌群，還可能通過使用這些特定細(xì)菌的同類型菌群作為益生菌，或者選擇通過使用益生元和其他日糧添加劑，還可以通過糞便腸道轉(zhuǎn)移增加其豐度[4-6]。

3 小結(jié)

未來對(duì)腸道菌群研究很重要的一個(gè)方面就是要弄清楚菌群的組成是如何對(duì)動(dòng)物的健康和生長(zhǎng)起到貢獻(xiàn)作用。目前的研究數(shù)據(jù)主要是描述性的，沒有準(zhǔn)確回答菌群組成對(duì)動(dòng)物生理變化的本質(zhì)原因。盡管已經(jīng)證明菌群的組成對(duì)代謝有重要作用，但是究竟是哪一類菌還需要進(jìn)一步定義。另外，同一種代謝功能是否由不同類的但是剛好有類似的代謝活動(dòng)的菌所提供這一問題也需要進(jìn)一步研究。描述腸道菌群是理解其對(duì)宿主發(fā)揮何種功能的第一步，因此，未來研究工作應(yīng)該集中在功能性分析上。

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Relationship between Intestinal Microflora Characteristics and Pig Growth

CHEN Peng1,DING Wuyi2

（1.Beijing Enhalor Biotechnology Co.,Ltd.,Beijing 100081,China;2.Ganzhou Institute of Animal Husbandry,Ganzhou 341000,Jiangxi China）

Colonization of the GIT by the microbiota plays an critical role not only for the overall well-being of the pig,but also for its nutrition,performance and quality of the products produced.Myriad of factors influences the diversity and activity of the GIT microbiota,including the age of the pig,the environment inhabiting,antimicrobial agents,dietary composition,feed additives,feed processing,disease load,weaning,season,stress and genes.These factors,can interact to make the study of the gut microbiota difficult.The characterization of the gut microbiota of swine has become an active area of research in recent years,especially as the adaptation of high-throughput sequencing methods have continued to expand.This article described the progress of intestinal microflora research and dis?cussed the changes of intestinal microflora,the relationship between growth performance and intestinal microflora of piglets during weaning period.

swine;gut microbia;growth

S828；S852.6

A

1001-0084（2017）11-0001-04

2017-09-23

陳鵬（1983-），男，黑龍江哈爾濱人，博士，主要從事生物飼料和添加劑的研究。