Increasing buffering capacity enhances rumen fermentation characteristics and alters rumen microbiota composition of high-concentrate fed Hanwoo steers

The buffering capacity of buffer agents and their effects on in vitro and in vivo rumen fermentation characteristics, and bacterial composition of a high-concentrate fed Hanwoo steers were investigated in this study. Treatments were comprised of CON (no buffer added), BC(0.3%) (low buffering capacity, 0.3% buffer), BC(0.5%) (medium buffering capacity, 0.5% buffer), and BC(0.9%) (high buffering capacity, 0.9% buffer). Four Hanwoo steers in a 4 × 4 Latin square design were used for the in vivo trial to assess the effect of treatments. Results on in vitro experiment showed that buffering capacity, pH, and ammonia–nitrogen concentration (NH(3)-N) were significantly higher in BC(0.9%) and BC(0.5%) than the other treatments after 24 h incubation. Individual and total volatile fatty acids (VFA) concentration of CON were lowest compared to treatment groups. Meanwhile, in vivo experiment revealed that Bacteroidetes were dominant for all treatments followed by Firmicutes and Proteobacteria. The abundances of Barnesiella intestinihominis, Treponema porcinum, and Vibrio marisflavi were relatively highest under BC(0.9%,) Ruminoccocus bromii and Succiniclasticum ruminis under BC(0.5%), and Bacteroides massiliensis under BC(0.3%.) The normalized data of relative abundance of observed OTUs’ representative families have grouped the CON with BC(0.3%) in the same cluster, whereas BC(0.5%) and BC(0.9%) were clustered separately which indicates the effect of varying buffering capacity of buffer agents. Principal coordinate analysis (PCoA) on unweighted UniFrac distances revealed close similarity of bacterial community structures within and between treatments and control, in which BC(0.9%) and BC(0.3%) groups showed dispersed community distribution. Overall, increasing the buffering capacity by supplementation of BC(0.5%) and and BC(0.9%) buffer agents enhanced rumen fermentation characteristics and altered the rumen bacterial community, which could help prevent ruminal acidosis during a high-concentrate diet.