Investigation On The Effects Of Feeding And Altitude On Gut Microbial Composition And Structure Of Tibetan Pigs

Tibetan pig is one of the most famous Chinese indigenous pig breeds.Tibetan pigs in localization has been raised in a half-pastured way,and has also been domesticated with many favourable features,such as good resistance to roughage feed,stress and disease resistance.However,the mechanism about formation of these characteristics remains unclear.Here we performed a survey on gut microbiotal communities of 66 Tibetan pigs raised in different feeding conditions and altitudes using 16 S rRNA gene sequencing,with the aim to identify the gut microbes significantly enriched in Tibetan pigs or Tibetan-specific gut microbes.We also investigated the effects of gut microbial composition on Tibetan pigs' characteristics.We analyzed the gut microbial composition and the interaction among microbes in Tibetan pigs.At the phylum level,Bacteroidetes and Firmicutes were the two dominant bacteria in all tested Tibetan pigs.At the genus level,we found 9 core bacterial genera with high abundance,which occupied about 38.3% of the total sequencing reads.The top three genera in relative abundances of these 9 core bacterial genera were Prevotella,Treponema and Succinivibrio.According to the Spearman rank correlation coefficient,we constructed the interaction network of the bacterial genera,and found that these 9 core bacterial genera were at the center of the network as the nodes.We analyzed the influences of feeding,altitudes and age in the phylogenetic composition and diversity of gut microbiota of Tibetan pigs by ADSOINS analysis.We found that feeding had the most significant effect on gut microbioal structure.And that,altitudes and age also had significant effects on gut microbial composition of Tibetan pigs.The Tibetan pigs fed with green fodder which contained high concentration of fibre had the greatest Alpha diversity of gut microbiota,followed by Tibetan pigs fed with concentrated feed and starch-enriched forage.Bacteroides,Oscillospira,Parabacteroides and YRC22 were significant enriched in the Tibetan pigs fed with concentrated feed,while Lachnospira,Faecalibacterium and Blautia,which produce short-chain fatty acids by fermenting diet starch,showed a higher abundance in starch-feeding Tibetan pigs.Moreover,Bifidobacterium,RFN20,Allobaculum and Turicibacter were enriched in Tibetan pigs fed with green fodder.Altitude also showed significant effect on the gut microbial composition of Tibetan pigs.We found that Tibetan pig lived in 2146 m had the greatest Alpha diversity of gut microbiota,while Tibetan pigs lived in localizations above 3000 m had the lowest Alpha diversity.We found that the relative abundances of 28 OTU and Anaeroplasma were increased with the altitude.In addition,age also had the significant impact on the gut microbiota structure of Tibetan pigs.The Alpha diversity of piglets was much lower than that of adult.At the genus level,Prevotella was significant enriched in piglets.We compared the gut microbial composition between Tibetan pigs and other pig breeds,including Duroc,Erhualian and Bamaxiang,and found that Tibetan pigs had the highest Alpha diversity in shannon index.Verrucomicrobia,which might be associated with disease resistance,and Treponema and Succinivibrio which are related to crude fibre metabolism,showed high abundances in Tibetan pigs.The predicted function capacity analysis of gut microbiome also indicated that the gut microbes enriched in Tibetan pigs and Tibetan pig-specific microbes might be associated with resistance to roughage feed,stress and disease resistance of Tibetan pigs.The results from this study will help us to understand the mechanism of gut microbiome in resistance to roughage feed,stress and disease resistance of Tibetan pigs,and will promote the development and utilization of Tibetan pigs.