Changes in vitro rumen fermentation, methane production and microbial populations in response to green tea extract

This research was conducted to evaluate the influence of adding increasing levels (0, 250, 500,750, and 1000 μg/mL buffered rumen fluid) of green tea ethanol extract (GTEE) to a basal substrate (50% roughage: 50% concentrate formulated with 50% barley and 50% corn grain) on rumen fermentation, methane emissions, and population of microorganism under in vitro experiment. The potential of gas production (A), methane emission, and methane ratio (mL/mL total gas 24 h) were linearly decreased by increasing the dose of GTEE (p<.001). The control group has the highest methane emission (p<.05), while it was the lowest (p<.05) at a dose of 1000 GTEE (47.74 versus 24.23 mL/g DM). In vitro digestibility of dry and organic matter were negatively affected by GTEE (L and Q; p<.001). The addition of GTEE significantly decreased total volatile fatty acids (TVFA) and N-NH3 concentration (L, p<.001), and also changed the VFA profile compared to the control group by decreasing and increasing the acetate and the propionate proportions (p<.001). The highest decrease in total protozoa population (93%), total fungi (38%), and methanogenic archaea (95%) compared to the control group was observed at the highest dose (1000) of GTEE. The addition of GTEE stimulates the population of Prevotella ruminicola and Selenomonas ruminantium, but Butyrivibrio fibrisolvent population was inhibited, in different supplementation doses. The lowest supplementation level (250 μg/mL) seems to have the most benefits on the in vitro fermentation parameters with minimum negative effects on nutrient digestibility. It can be concluded that GTEE can potentially be used to manipulate ruminal fermentation patterns.Highlights Reducing the methane concentration through the anti-protozoal activity of green tea extract improve rumen fermentation patterns by decreasing acetate and N-NH3 concentration and increasing the propionate proportions. Although the in vitro anti-acidosis potential of GTEE is not as much as monensin, the anti-acidosis potential is significantly increased by increasing GTEE dose compared to the control. The decrease in in vitro total gas, CH4 production, and dry- and organic-matter digestibility on the addition of GTEE could be attributed to the antimicrobial action of GTEE.