Changes in the diversity of rumen bacterial community by a sudden change to a high-concentrate diet in Korean domestic ruminants.

Objective: To investigate changes in rumen fermentation characteristics and bacterial community by a sudden change to a high concentrate diet (HC) in Korean domestic ruminants.

Methods: Major Korean domestic ruminants (each of four Hanwoo cows; 545.5 ± 33.6 kg, Holstein cows; 516.3 ± 42.7 kg, and Korean native goats; 19.1 ± 1.4 kg) were used in this experiment. They were housed individually and were fed ad libitum with a same TMR (800 g/kg timothy hay and 200 g/kg concentrate mix) twice daily. After two-week feeding, only the concentrate mix was offered for one week in order to induce rapid rumen acidification. The rumen fluid was collected from each animals twice (on week 2 and week 3) at 2h after morning feeding using an oral stomach tube. Each collected rumen fluid was analyzed for pH, volatile fatty acid (VFA), and NH3-N. In addition, differences in microbial community among ruminant species and between normal and an acidosis condition were assessed using two culture-independent 16S PCR-based techniques (T-RFLP and quantitative real-time PCR).

Results: The HC decreased ruminal pH and altered relative concentrations of ruminal VFA (p<0.01). Total VFA concentration increased in Holstein cows only (p<0.01). Terminal restriction fragment length polymorphism and real-time quantitative PCR analysis using culture-independent 16S PCR-based techniques, revealed rumen bacterial diversity differed by species but not by HC (p<0.01); bacterial diversity was higher in Korean native goats than Holstein cows. HC changed the relative populations of rumen bacterial species. Specifically, the abundance of Fibrobacter succinogenes was decreased while Lactobacillus spp. and Megasphaera elsdenii were increased (p<0.01).

Conclusion: HC altered the relative populations, but not diversity, of the ruminal bacterial community, which differed by ruminant species.