Abstract
: 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.
Highlights
Methane production in the rumen is a nutritionally wasteful process which represents 2 to 15% feed energy loss (Moss, 1993)
Methane production at 0% bromoethanesulfonic acid (BES) was higher with mixed substrate (p
Excess amount of concentrate over the level used in present study may have decreased protozoal growth and reduced methane production in the rumen compared to roughage alone as reported in previous studies (Moe and Tyrrell, 1979; Moss et al, 1993)
Summary
Methane production in the rumen is a nutritionally wasteful process which represents 2 to 15% feed energy loss (Moss, 1993). Various compounds have been used to decrease ruminal methane production by various methods (Bhatta et al, 2007), and some of examples are: ionophores Halogenated compounds such as bromoethanesulfonic acid (BES) are known to be the most effective inhibitors due to their direct inhibitory effects to methanogenic bacteria. Martin and Macy (1985) observed that 30 μM BES reduced methane production by 76% in mixed cultures of rumen fluid. Ungerfeld et al (2004) observed different sensitivity to methane inhibitors including BES by pure culture of ruminal methanogens. Methanobrevibacter ruminantium was the most sensitive to BES, Methanosarcina mazei was the least sensitive and Methanomicrobium was intermediate
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