Herbal feed additives containing essential oil: 1. Impact on the nutritional worth of complete feed in vitro

This study was taken up to assess the impact of supplementing herbal feed additives [HFAs; fruit of Myristica fragrans (Jayphall), seeds of Anethum sowa (Suva), fruit of Apium graveolens (Ajmo), fruit of Cuminum cyminum (Jeera), bark of Cinnamonum zeylanicum (Dalchini), or whole plant of Eclipta alba (Bhangro)] containing essential oils as active component on the nutrient utilization and methane production using wheat straw-based total mixed ration (TMR) as a substrate by in vitro gas production technique. The essential oil content was the highest (P < 0.01) in M. fragrans followed by E. alba and A. sowa. In addition to essential oils, these HFAs also contained saponins, tannins, and antioxidants. The HFAs were supplemented at 1-3% of substrate dry matter (DM). The data were analyzed by 6 × 4 factorial design. Irrespective of level of HFA, the net gas production (NGP) and metabolizable energy (ME) availability was the highest (P < 0.01) in TMR supplemented with C. zeylanicum comparable with E. alba, but higher than TMR supplemented with other HFAs. Supplementation of TMR with different HFAs did not affect the digestibility of neutral detergent fiber (NDF) and true organic matter (TOM) and partitioning factor (PF). The total volatile fatty acids (VFAs), acetate, propionate (P < 0.01), and butyrate (P < 0.05) production was the highest in TMR supplemented with A. sowa, and the lowest was observed in TMR supplemented with C. cyminum. The isobutyrate and valerate production was also the highest (P < 0.01) in diet supplemented with A. sowa, but isovalerate production was the highest (P < 0.01) in diet supplemented with C. zeylanicum. The A:P ratio was the best in TMR supplemented with A. sowa. The efficiency of rumen fermentation was the highest, and efficiency of conversion of hexose to methane was the lowest in diet supplemented with A. sowa as compared to all other supplements. The in vitro methane production expressed as either percent of NGP, ml/100 mg DM of substrate/24 h, or as ml/100 mg of digestible OM/24 h was the lowest in TMR supplemented with A. sowa. The ammonia nitrogen production from TMR supplemented with M. fragrans and A. sowa was comparable, but significantly (P < 0.01) lower than TMR supplemented with other HFAs. Irrespective of the nature of HFA, the NGP and ME availability were significantly (P < 0.01) higher in TMR supplemented with HFAs at all levels as compared to un-supplemented TMR. As compared to control, the digestibility of NDF and that of TOM was depressed slightly in all the HFA-supplemented TMRs. The supplementation of HFAs at 2% of substrate DM improved (P < 0.01) the production of total VFAs, acetate, and propionate, and that of isovalerate in comparison to the un-supplemented TMR. The acetate to propionate ratio increased (P < 0.01) with the increase in the level of supplementation of HFAs containing essential oils. The methane and ammonia productions were depressed significantly when TMR was supplemented at 2% level of HFAs as compared to control TMR. It was concluded that supplementation of TMR with A. sowa at 2% of substrate was fermented better as indicated by the production of total and individual VFA, methane, and ammonia as compared to TMR supplemented with other HFA or un-supplemented TMR.