户外放养的猪总是比圈养和严密隔离饲养的猪看起来“脏”。但英国一项研究显示，这些户外放养的“脏”小猪实际上更健康。
英国阿伯丁大学等机构研究人员日前在《BMC生物学》期刊上报道了这一发现。他们将54只基因谱系近似的小猪平均分成3组，一组在户外放养，另一组在室内圈养，最后一组不仅在严格隔离的环境下饲养，还被定时喂食抗生素。
研究人员分别在实验初期、小猪断奶期和接近成熟期对它们进行了分析。结果发现，在户外放养的那一组小猪中，肠道里约90％的细菌都属于壁厚菌门，这类细菌的大部分都对健康有益，有助于控制大肠杆菌和沙门氏菌等致病菌；而室内圈养的小猪肠道内这种细菌只占70％，隔离饲养的小猪肠道内这种细菌仅为50％左右。
研究人员说，肠道菌群的差异甚至还引起与免疫系统相关的基因变化，在隔离饲养的小猪体内，与发炎免疫反应有关的基因表达更多；而在户外放养的小猪体内，与免疫细胞T细胞相关的基因表达更多。
研究人员认为，实验表明，看起来“脏”的环境反而更有利于小猪的健康和免疫系统发展。研究人员说，虽然在小猪身上得到的实验结果不能直接套用到人身上，但两者肠道内微生物的相似性，使得这一结果对人类也具有参考价值。（生物谷Bioon.com）
小型猪是生物医学研究中应用最为广泛的非啮齿类大型实验动物之一，具有其它实验动物不可替代的优越性，而且作为异种器官移植最可能的供体成为研究热点，因此小型猪的研究和开发利用受到生物医药界的普遍关注。
“2010年广州-东莞首届国际小型猪论坛”将于2010年1月8日在广州召开，详情点击：http://www.minipig.org/
生物谷推荐原始出处：
BMC Biology 2009, 7:79doi:10.1186/1741-7007-7-79
Environmentally-acquired bacteria influence microbial diversity and natural innate immune responses at gut surfaces
Imke E Mulder* 1 , Bettina Schmidt* 1 , Christopher R Stokes2 , Marie Lewis2 , Mick Bailey2 , Rustam I Aminov1 , James I Prosser3 , Bhupinder P Gill4 , John R Pluske5 , Claus-Dieter Mayer6 , Corran C Musk1 and Denise Kelly1
1Gut Immunology Group, University of Aberdeen, Rowett Institute of Nutrition and Health, Greenburn Road, Aberdeen AB21 9SB, UK
2Veterinary Pathology, Infection & Immunity, Langford House, Langford, Bristol, BS40 5DU, UK
3Institute of Biological and Environmental Sciences, University of Aberdeen, St Machar Drive, Aberdeen AB24 3UU, UK
4Agricultural and Horticultural Development Board, Winterhill House, Snowdon Drive, Milton Keynes MK6 1AX, UK
5School of Veterinary and Biomedical Sciences, Murdoch University, Murdoch, WA 6150, Australia
6Biomathematics & Statistics Scotland, University of Aberdeen, Rowett Institute of Nutrition and Health, Greenburn Road, Aberdeen AB21 9SB, UK
Background
Early microbial colonization of the gut reduces the incidence of infectious, inflammatory and autoimmune diseases. Recent population studies reveal that childhood hygiene is a significant risk factor for development of inflammatory bowel disease, thereby reinforcing the hygiene hypothesis and the potential importance of microbial colonization during early life. The extent to which early-life environment impacts on microbial diversity of the adult gut and subsequent immune processes has not been comprehensively investigated thus far. We addressed this important question using the pig as a model to evaluate the impact of early-life environment on microbe/host gut interactions during development.
Results
Genetically-related piglets were housed in either indoor or outdoor environments or in experimental isolators. Analysis of over 3,000 16S rRNA sequences revealed major differences in mucosa-adherent microbial diversity in the ileum of adult pigs attributable to differences in early-life environment. Pigs housed in a natural outdoor environment showed a dominance of Firmicutes, in particular Lactobacillus, whereas animals housed in a hygienic indoor environment had reduced Lactobacillus and higher numbers of potentially pathogenic phylotypes. Our analysis revealed a strong negative correlation between the abundance of Firmicutes and pathogenic bacterial populations in the gut. These differences were exaggerated in animals housed in experimental isolators. Affymetrix microarray technology and Real-time Polymerase Chain Reaction revealed significant gut-specific gene responses also related to early-life environment. Significantly, indoor-housed pigs displayed increased expression of Type 1 interferon genes, Major Histocompatibility Complex class I and several chemokines. Gene Ontology and pathway analysis further confirmed these results.
Conclusion
Early-life environment significantly affects both microbial composition of the adult gut and mucosal innate immune function. We observed that a microbiota dominated by lactobacilli may function to maintain mucosal immune homeostasis and limit pathogen colonization.
