Effect of saponin containing plants on greenhouse gas emissions from ruminants

The microbial population of the rumen allows to use the cellulose as source of energy and to metabolize non-protein nitrogen. However, these features are responsible of methane and ammonia production. Methane is eructated and represent an energetic loss of around 10% of the ingested energy from the feed. Furthermore, methane contribute significantly to the greenhouse gas emissions worldwide. To reduce this effect, rumen fermentation may be shifted by feed additives.

 

Different investigations showed that saponin containing plants  have an antiprotozoal activity and an effect on bacteria similar to the ionophore antibiotics. These plant extracts have shown the potential to reduce ammonia rejections (up to 30% for Yucca schidigera) and methane (up to 30% for Sapindus saponaria). Mechanisms of action are not totally described for the moment, but hypothesis have been formulated. On the one hand, an improved efficacy of the microbial protein synthesis and a reduced proteolysis in the presence of saponins in the rumen would allow the reduction of NH3 production. On the other hand, an inhibition of the saponins on both Archaea methanogens and protozoa would reduce the methane emissions.