Effects of the methane-inhibitors nitrate, nitroethane, lauric acid, Lauricidin® and the Hawaiian marine algae Chaetoceros on ruminal fermentation in vitro

The effects of several methane-inhibitors on rumen fermentation were compared during three 24 h consecutive batch cultures of ruminal microbes in the presence of nonlimiting amounts of hydrogen. After the initial incubation series, methane production was reduced greater than 92% from that of non-treated controls (25.8 ± 8.1 μmol ml−1 incubation fluid) in cultures treated with nitroethane, sodium laurate, Lauricidin® or a finely-ground product of the marine algae, Chaetoceros (added at 1, 5, 5 and 10 mg ml−1, respectively) but not in cultures treated with sodium nitrate (1 mg m1−1). Methane production during two successive incubations was reduced greater than 98% from controls (22.5 ± 3.2 and 23.5 ± 7.9 μmol ml−1, respectively) by all treatments. Reductions in amounts of volatile fatty acids and ammonia produced and amounts of hexose fermented, when observed, were most severe in sodium laurate-treated cultures. These results demonstrate that all tested compounds inhibited ruminal methane production in our in vitro system but their effects on fermentation differed.