Characterization of rumen microbial community composition of buffalo fed diets varying in forage:concentrate ratio
Murrah and Nili-Ravi are two widely used dairy water buffalo breeds in Asian countries. In this study, we investigated the diversity of ruminal microbes in six Murrah and six Nili-Ravi water buffalos maintained in China. The buffalos were separated into two groups; each group contained three Murrah and three Nili-Ravi buffalos, and two different diets (with forage to concentrate ratios of 3.2 or 1.6) were fed to the two groups. After feeding the diets for 15 days, ruminal fluid was sampled by stomach tube before the morning feeding. The bacterial and archaeal 16S rRNA genes and the ciliate protozoal 18S rRNA genes from the 12 rumen samples were sequenced by multiplex 454 Titanium pyrosequencing, and the sequence data was analyzed using QIIME 2.0 software. Our results showed that at the phylum level, Bacteroidetes was the predominant bacterial group, accounting for 42 % to 72% of total bacteria, followed by Firmicutes, Fibrobacter and Proteobacteria. At the genus level, Prevotella dominated, accounting for 22 % to 58% of total bacteria, followed by Fibrobacter, Paludibacter and Ruminococcus. While there were differences between the bacterial community compositions of different animals, there was no obvious correlation of bacterial community composition, at the phylum or genus level, with the diets or with buffalo breeds. For the Archaea, Methanobrevibacter-related organisms were the dominant group, accounting for around 80% of the total, followed by Methanoplasmatales (RCC, 15%) and Methanosphaera (3%). Similar to the bacterial community, there was no clear correlation of the Archaea community profile with diet or buffalo breed. The ciliate protozoal communities differed between the samples analysed, although Entodinium was the most abundant group of ciliates in every sample, accounting for more than 40% of total protozoa. The second largest ciliate group varied in different samples with Isotricha, Polyplastron or Dasytricha the dominant genera after Entodinium. In summary, the predominant genera observed in the bacterial, archaeal and ciliate protozoal communities in rumen samples of Murrah and Nili-Ravi buffalo were Prevotella, Methanobrevibacter and Entodinium respectively. Overall, the buffalo rumen microbial communities varied greatly between individual animals, regardless of the diet composition or the buffalo breed used in this study.
Keywords: Buffalo; rumen; microbial community; forage to concentrate ratio;