Effect of concentrate to roughage ratios on rumen flora structure in yaks

The objective was to investigate the effects of concentrate to roughage ratio on rumen flora structure in yaks. Thirty-six healthy male yaks of similar weight were randomly assigned to three groups of 12 animals, each. The groups were fed a 50 ꞉ 50 (A group), 65 ꞉ 35 (B group), and 80 ꞉ 20 (C group) concentrate to roughage ratios, respectively, for a preliminary period of 15 d and an experimental period of 90 d. Before morning feeding on the 90th day of the trial period, rumen fluid was collected by gavage, and rumen microbial community structures were analyzed using 16Sr DNA high-throughput sequencing. The results showed the following: 1) a total of 3 354 operational taxonomic units (OTUs) were established, of which 1 851 OTUs were shared between the treatment groups, accounting for 55.19% of the total number; the number of species, Chao1 index, Shannon index, and a PD whole tree of rumen bacteria showed a significant linear decrease with increasing diet concentrate to roughage ratios (P < 0.05). 2) At the phylum level, the relative abundance of Firmicutes and Actinobacteria was significantly and linearly positively correlated ( P < 0.05) with the ration concentrate to roughage ratio. By contrast, the relative abundance of Bacteroidetes decreased significantly and linearly ( P < 0.05) with the increase of the diet concentrate ratio; the relative abundance of Verrucomicrobia was significantly higher in test group B ( P < 0.05) than in the other two groups. The relative abundance of Verrucomicrobia was significantly higher than that of the other two groups. 3) At the genus level, with the increase of diet concentrate to roughage ratios, the relative abundances of Prevotella_1, Ruminococcaceae_NK4A214_group, andAcetitomaculum showed a significant linear increase (P < 0.05), while the relative abundances of Ruminococcus_2 and Lachnospiraceae_NK3A20 group were significantly decreased (P < 0.05). In conclusion, the total number and diversity of rumen bacteria in yaks were significantly influenced by the ratio of concentrate to roughage, and the growth of some degradation bacteria in the rumen was inhibited by high concentrate to roughage ratios.