The use of certain medicinal plant extracts reduced in vitro methane production while improving in vitro organic matter digestibility

Some medicinal plants have the tendency to manipulate the rumen microbial ecosystem, which in turn might reduce methane (CH4) emissions. The anti-methanogenic activities of leaf fraction of Piper betle, Aloe vera, Carica papaya, Azadirachta indica, Moringa oleifera, Tithonia diversifolia, Jatropha curcas and Moringa oleifera pods were studied at different doses. The plant materials were extracted with pure methanol and subsequently reconstituted at the rate of 25, 50, 75 and 100 mg in 1000 mL distilled water. Four mL of each plant extracts preparation was anaerobically incubated with 400 mg Eragrostis curvula hay in four replicates and the experiment was repeated five times. Plant extracts of P. betle and A. vera significantly increased total gas produced whereas other extracts recorded lesser or similar values to the control group. Leaf extracts of A. indica, C. papaya, J. curcas, M. oleifera, T. diversifolia and M. oleifera pods all significantly reduced CH4 volume at dosages of 25 and 50 mg/L due to the activities of their phytochemicals. Total volatile fatty acids and in vitro organic matter digestibility values recorded for all extracts were generally superior when compared with the control. Methane yield per unit of total gas were significantly lower in extracts of T. diversifolia, M. oleifera, A. indica, M. oleifera pods whereas it is higher in P. betle and A. vera. It can be concluded from the study that methanolic extracts of A. indica, C. papaya, J. curcas, M. oleifera, M. oleifera pods and T. diversifolia resulted in reduced CH4 production, and thus can be used potentially to manipulate rumen condition, improve feed digestibility and reduce enteric CH4 emission from ruminants. However, the in vitro results needs to be verified using in vivo studies by administering concentrated crude extracts at a rate of 25 mg or 50 mg per kg of roughage feed for small ruminants.