Caffeic acid modulates methane production and rumen fermentation in an opposite way with high-forage or high-concentrate substrate in vitro.

BACKGROUND Plant secondary metabolites including tannins, saponins or phenolic acids possess potential methane (CH4 ) inhibition bioactivity. Caffeic acid (CA) as one of typical phenolic acids served as a promising rumen CH4 inhibitor, but the underlying mechanisms and investigations with typical formulated rations are still not well-documented. Therefore, a batch culture study was conducted to investigate the effects of CA on methanogenesis, rumen fermentation and growth of ruminal microorganisms when high-forage or high-concentrate substrates are fermented. RESULTS After 48 h incubations, adding CA up to 40 g/kg DM linearly reduced (P 0.05)16S rDNA copy numbers of methanogens and R. albus. CONCLUSION Caffeic acid inhibited in vitro methanogenesis and rumen fermentation with high-forage substrate incubated. Contrarily, CA benefited in vitro fermentation and enhanced methanogenesis with high-concentrate substrate incubated. It suggests that CA modulates methanogenesis and rumen fermentation mainly by affecting the growth of cellulolytic bacteria in vitro. This article is protected by copyright. All rights reserved.