Effect of Essential Oils of Eucalyptus (Eucalyptus globulus Labill) and Angelica (Heracleum persicum Desf. ex Fischer) on In vitro Ruminal Fermentation, Protozoal Population and Methane Emission Using Afshari Sheep Inoculum

The effect of eucalyptus (Eucalyptus Globulus Labill;EGEO) and Angelica (Heracleum Persicum Desf. ex Fischer; HPEO) Essential Oils was assessed at the levels of 0, 3, 30, 300 or 3000 (µl 30 ml-1) on in vitro fermentation of buffered rumen fluid from 3 castrated male sheep. The fermentation kinetics were estimated after 54 hours incubation. The fermentation kinetic values, In Vitro Gas Production (IVGP), Methane Production (MP), ammonia-N (NH3-N) concentration, Organic Matter Degradability (IVOMDe), Partitioning Factor (PF), Microbial Mass (MM), Volatile Fatty Acids (VFA) concentrations and protozoa population were evaluated. The results showed that EGEO supplementation at 300µl increased the insoluble fraction (b) (P= 0.027). Cumulative IVGP at 54 hours was the lowest for EGEO (P= 0.014) and HPEO (P= 0.001) at 3,000 µl. The HPEO supplementation at 30 and 3,000 µl decreased (P= 0.036) the constant rate (c) of gas production during incubation 54 hours. The EGEO inclusion improved GP in 24 hours at 3 µl, but inhibited fermentation at 3,000 µl (P = 0.004), whereas addition of HPEO inhibited fermentation at 3,000 µl (P= 0.000) only. The addition of EGEO and HPEO (P= 000) inhibited MP at all levels. HPEO treatments reduced (P= 0.005) the NH3-N concentration at 3 and 3,000 µl levels. The IVOMDe was increased at dose rates of 3, 30 or 300 µl EGEO, but decreased at 3000 µl of HPEO. At the inclusion of 3,000 µl of EGEO and HPEO, PF, MM and Efficiency of Microbial Mass (EMM) were enhanced (P= 0.001). Apart from the inclusion level of 300 µl, total VFA concentrations were decreased by EGEO (P= 0.002) and HPEO (P= 0.001). The EGEO and HPEO treatments showed antiprotozoal activity. It is suggested that EGEO and HPEO could be added at the level of 300 µl 30 ml-1 to improve ruminal fermentation (i.e. increasing EMM and decreasing MP and protozoa population), which may lead to better nutrient utilization and animal growth.