Effects of malic acid and unsaturated fatty acids on methano genesis and fermentation by ruminal microbiota in vitro

Abstract

Methanogens and protozoa in the rumen negatively affect rumen function by wasting ingested energy. It is desirable to modulate rumen fermentation by cost-effective dietary intervention. The objective of this study was to evaluate effects of unsaturated CI 8 fatty acids (oleic, linoleic and linolenic acids), either alone or in combination with malic acid on in vitro ruminal fermentation, protozoa and Methanobacteriumformicicum. Rumen fluid collected from ruminally fisulated lactating Chinese Holstein cows served as the inoculum and the diet consisted of alfalfa hay and corn (50:50). The results showed addition of unsaturated fatty acids tended to increase fermentation pH (p>0.05) and degree of unsaturation of fatty acids tended to affect such effect on thepH (p>0.05). Acetate, butyrate, total VFA, total gas production and methane production decreased (p<0.01) with increasing degree of unsaturation of CI 8 fatty acids but addition of malic acid did not have any additive or synergistic effect except for propionate which was decreased by the addition of malic acid (p<0.01). Both malate and the unsaturated fatty acids, either alone or in combination, decreased methane production (p<0.01) with combination of these two types of acid further decreasing methane production. Except for oleici acid that decreased population of M. formicicum decreased (p<0.01), either protozoa or M. formicicum was affected by these fatty acid and malic acid. It was concluded that when used together, malic acid and fatty acids could reduce methane emission without negative impairing fermentation in vitro. © Medwell Journals, 2012.