Assessment of potential of some tannins and saponins containing herbs on digestibility of nutrients, fermentation kinetics and enteric methane production under different feeding systems: An in vitro study

The study was undertaken to assess the effect of some tannin and saponin containing herbs, viz. Anarchal, Amla, Baheda and Rohitaka at four levels (0–3% of substrate) on digestibility of nutrients and enteric methane (CH4) production under different feeding systems (roughage to concentrate (R:C) ratios; 80:20, 75:25, 70:30 and 65:35 on DM basis) in vitro in 4×4×4 factorial design. Irrespective of level of herbs and R:C ratios, the fermentation parameters and CH4 mitigation potential varied significantly among different herbs. Digestibility of OM, TVFA and A:P ratio for Anarchal whereas NGP, ME availability, VFA efficiency and depression in CH4 production as % of DM at t1/2 for Rohitaka were observed to be highest. Irrespective of type of herbs and R:C ratios, the net gas production (NGP), digestibility of NDF, ME availability and TVFA increased linearly with increase in the level of supplementation of herbs and was significantly higher at 2 and 3% level; however, 2%, level had an edge over 3% level w.r.t. partitioning factor, VFA efficiency and A:P ratio. At t1/2, CH4 production as percent of NGP was observed to be lowest at 2 and 3% level. Irrespective of type of herb and their level, NGP, digestibility, ME availability, and TVFAs increased linearly with increase in concentrate in TMRs. At t1/2, CH4 production as percent of NGP was lowest at 65:35 in comparison to others. It was concluded that best results on digestibility of nutrients, VFA production, ME availability and in reducing CH4 production was given by Anarchal and Rohitaka supplemented @ 2% of TMR with R:C ratio of 65:35 on DM basis.