Effects of three herbal feed additives on In Vitro fermentation pattern and methane production

The present study was taken up to assess the impact of supplementing total mixed ration (TMR) with three herbal feed additives (HFA), namely, dry extracts of Camellia sinensis leaves, Myrica nagi fruit and Acacia arabica bark at 0, 1, 2 and 3% levels on fermentation pattern and methane production by in vitro gas production technique. The three extracts differed in their content of total phenols, non-tannin phenols, true tannins, condensed tannins and hydrolysable tannins, as well as the contents of saponins and antioxidant activity. When tested in vitro, the dose of HFAs supplementation did not affect (P>0.05) the net gas production (NGP), digestibility of true OM and NDF, partitioning factor and ME values of TMR. However, both the NGP and ME values were apparently higher when HFA were supplemented at 2% level. The concentration of total volatile fatty acids (VFA), acetate and propionate were reduced (P<0.01), while that of branched-chain fatty acids was improved (P<0.01) at all doses of HFA supplementation. The VFA production was highest (P<0.01) with the A. arabica bark supplementation. The highest (P<0.01) efficiency of conversion of fermented hexose to VFA energy and the lowest efficiency of conversion of hexose to methane energy was observed in the diet supplemented with HFA at 2% level. The in vitro methane production from TMR was reduced (P<0.05) when supplemented with C. sinensis or A. arabica at 2% level. It was concluded that Acacia arabica bark when supplemented to total mixed ration at 2% level, resulted in the highest in vitro concentration of VFAs, microbial biomass production and supressed the methane emission as compared to control and other supplemented groups.