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In vitro screening of the potential of numerous plant species as antimethanogenic feed additives for ruminants

Bodas, R., López, S., Fernández, M., García-González, R., Rodríguez, A.B., Wallace, R.J., González, J.S.
Animal feed science and technology 2008 v.145 no.1-4 pp. 245-258
ruminant nutrition, methane production, feed additives, plant extracts, natural additives, Carduus pycnocephalus, Rheum, rumen fermentation, in vitro studies, digestibility, screening, ruminants
A screening experiment was conducted to evaluate the potential of 450 plant species as antimethanogenic additives in ruminant feeds. Effects of addition of these plants, which were incorporated to the fermentation substrate as a dry powder, on ruminal fermentation, fibre digestion and methane production were studied in vitro in batch cultures of mixed rumen microorganisms. Serum bottles containing 500mg of substrate (500galfalfahay/kg, 400ggrasshay/kg and 100g barley grain), 50mg of the plant additive tested and 50ml of buffered rumen fluid (10ml sheep rumen fluid+40ml culture medium) were incubated at 39°C for 24h. After incubation, gas and methane production, pH and volatile fatty acid (VFA) concentration in the incubation medium and dry matter and neutral detergent fibre disappearance were recorded. Of the 450 samples tested, 35 decreased methane production by more than 15% versus those with corresponding control cultures and, with 6 of these plant additives, the depression in methane production was more than 25%, with no adverse effects on digestibility, total gas and VFA production. With these six samples, incubations were repeated to confirm their effects on methane production in vitro. Some candidates, in particular Rheum nobile and Carduus pycnocephalus, consistently decreased methane production without adversely affecting other parameters of the rumen fermentation.