In Vitro Screening of East Asian Plant Extracts for Potential Use in Reducing Ruminal Methane Production

Indiscriminate use of antibiotics can result in antibiotic residues in animal products; thus, plant compounds may be better alternative sources for mitigating methane (CH) production. An in vitro screening experiment was conducted to evaluate the potential application of 152 dry methanolic or ethanolic extracts from 137 plant species distributed in East Asian countries as anti-methanogenic additives in ruminant feed. The experimental material consisted of 200 mg total mixed ration, 20 mg plant extract, and 30 mL diluted ruminal fluid-buffer mixture in 60 mL serum bottles that were sealed with rubber stoppers and incubated at 39 °C for 24 h. Among the tested extracts, eight extracts decreased CH production by >20%, compared to the corresponding controls: stems of var. stems of , fruit of , seeds of , seeds of , leaves of , stem and bark of , and stems of . A confirmation assay of the eight plant extracts at a dosage of 10 mg with four replications repeated on 3 different days revealed that the extracts decreased CH concentration in the total gas (7-15%) and total CH production (17-37%), compared to the control. This is the first report to identify the anti-methanogenic activities of eight potential plant extracts. All extracts decreased ammonia (NH-N) concentrations. Negative effects on total gas and volatile fatty acid (VFA) production were also noted for all extracts that were rich in hydrolysable tannins and total saponins or fatty acids. The underlying modes of action differed among plants: extracts from var. , and resulted in a decrease in total methanogen or the protozoan population ( < 0.05) but extracts from other plants did not. Furthermore, extracts from decreased the population of total protozoa and increased the proportion of propionate among VFAs ( < 0.05). Identifying bioactive compounds in seeds of by gas chromatography-mass spectrometry analysis revealed enrichment of linoleic acid (18:2). Overall, seeds of could be a possible alternative to ionophores or oil seeds to mitigate ruminal CH production.