Screening the activity of plants and spices for decreasing ruminal methane production in vitro

Different plants, herbs and spices (158 samples) were tested in a screening trial to assess their potential to modify ruminal fermentation in vitro, in particular their effectiveness for decreasing methane production.In vitro incubations were carried in buffered rumen fluid at 39 °C and after 24 h of fermentation, gas production and pH were recorded, and gas and volatile fatty acids (VFA) were analysed. Residual matter was determined by filtration.Most of the plants tested did not cause any noticeable effect on the fermentation parameters studied. However, rhizomes and roots of Rheum officinale (rhubarb), bark of Frangula alnus (frangula or alder buckthorn) and bulbs of Allium sativum (garlic) decreased methane production and acetate to propionate ratio. Changes in ruminal fermentation observed in response to the addition of these plants were confirmed in subsequent in vitro assays. This is the first report to identify that rhubarb and frangula may contain active secondary compounds targeting ruminal methanogenic microorganisms.