Evaluation of three medicinal plants for methane production potential, fiber digestion and rumen fermentation in vitro

Effects of three selected medicinal plants on fermentation patterns and to evaluate their potential as antimethanogenic additives in ruminant feeds were studied. Effects of Nigella sativa, Rosmarinus officinalis and Zingiber officinale, which were added 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 500 mg of substrate (a mixture of 500 mg of alfalfa hay, 400 mg of grass hay and 100 mg of barley grain per gram), 50 mg of the plant tested and 50 ml of buffered rumen fluid (10 ml sheep rumen fluid + 40 ml culture medium) were incubated at 39 ºC for 24 h. 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. The amounts of methane produced after 24 hours of fermentation varied between 0.28 and 1.12mmol/gDM. A significant methane reduction was observed with monensin (75% less methane than control) and Nigella sativa (20% less methane than control) and no effect was observed with the other treatments. Further studies are warranted to confirm the antimethanogenic activity of Nigella sativa, establish a dose-response relationship, examine the stability in time of the effects, and test if the effects can be reproduced in vivo with animals.