Effect of 2-Bromoethanesulfonic Acid on In vitro Fermentation Characteristics and Methanogen Population

An in vitro incubation study was conducted to investigate effects of 2-bromoethanesulfonic acid (BES) on ruminal fermentation characteristics and methanogen population.BES at the final concentration of 0, 1 and 5 mM with two different substrates having a different ratio of timothy and concentrate (100% timothy vs. 40% timothy-60% concentrate) was incubated for 0, 24, 48 and 72 h in a 39°C incubator.Total DNA extracted from culture fluid was used as a template for real-time PCR to measure the population of methanogens.Four different primer sets were used for amplification of total bacteria, total methanogens, the order Methanobacteriales and the order Methanomicrobiales.BES reduced (p<0.01)total gas and methane production in a dose-dependent manner.BES at 5 mM inhibited methane production by more than 95% compared to the control.An interaction between substrate and level of BES in total gas and methane was detected (p<0.01).The decrease of methane production with increasing BES level was more pronounced on mixed substrate than on timothy alone.However, hydrogen production was increased by BES treatment (p<0.01).Total VFA concentration was not affected, but molar percentage of propionate and butyrate was increased and acetate to propionate ratio was reduced by BES treatment (p<0.01).BES did not affect the population density of total bacteria but reduced (p<0.01) the population of total methanogens, the order Methanobacteriales and the order Methanomicrobiales in a dose-dependent manner.The type of substrate did not influence the trend, although the magnitude of response was different between all-roughage and 40% roughage substrate.(