Rumen bacterial community evaluated by 454 pyrosequencing in dairy sheep fed marine algae. Rumen bacteria in ewes fed marine algae

Developing novel strategies to increase the content of bioactive unsaturated fatty acids (FA) in ruminant-derived products requires a deeper understanding of rumen biohydrogenation and bacteria involved in this process. Although high-throughput pyrosequencing may allow for a great coverage of bacterial diversity, it has hardly been used to investigate the microbiology of ruminal FA metabolism. In this study, 454 pyrosequencing were used to assess the effect of diet supplementation with marine algae (MA) on the rumen bacterial community of dairy sheep. Eleven lactating ewes were divided in 2 lots and offered a total mixed ration based on alfalfa hay and a concentrate (40:60), supplemented with 0 (Control) or 8 (MA) g of MA/kg of dry matter. After 54 d on treatments, animals were slaughtered and samples of rumen content and fluid were collected separately for microbial analysis. Pyrosequencing yielded a great coverage of bacterial diversity and allowed the identification of low abundant populations. This molecular approaches showed that relevant changes due to MA addition were observed within the major ruminal phyla, namely Bacteroidetes, Firmicutes and Proteobacteria. Decreases in the abundance of unclassified Bacteroidales, Porphyromonadaceae and Ruminococcaceae, and increases in as yet uncultured species of the family Succinivibrionaceae, might be related to a potential role of these groups in different pathways of rumen FA metabolism. Diet supplementation with MA had, however, no effect on the relative abundance of Butyrivibrio and Pseudobutyrivibrio genera. In addition, results from both 454 pyrosequencing indicate that the impact of MA was rather consistent in rumen content or fluid samples, despite inherent differences between these fractions in their bacterial composition.