Effect of different levels of fennel essential oil on in vitro gas production parameters and protozoa population of goat rumen

This study was conducted to evaluate the effect of different doses of fennel essential oil (100, 250, 500, 750 and 1000 µg) on in vitro gas production parameters and protozoa population using goat rumen fluid. Rumen fluid was obtained from six Markhoz goats before morning feeding via esophageal tube. Gas production during 96 hours of incubation was recorded. The effect of essential oil on total protozoa and different genus was investigated. Also, gas production after 24h, methane production and some of the other in vitro ruminal parameters were determined. Gas production potential (B) and fermentation rate (c) were decreased by inclusion of the essential oil (P<0.0001), while lag phase in low doses of the essential oil increased (P=0.004). The pH did not alter due to the additionof the essential oil, but ammonia nitrogen and total volatile fatty acids were declined at doses of 750 and 1000 µg of the essential oil. Gas 24h, methane production, in vitro organic matter digestibility and metabolizable energy decreased, while partitioning factor, microbial mass and its efficiency increased by adding the essential oil (P<0.0001). Adding fennel essential oil into fermentation media decreased total protozoa number and Entodinium spp and Isotricha spp (P<0.0001), but it had no effect on Diplodiniinae and Ophryoscolecinae populations. The results showed that the fennel essential oil may have selective antiprotozoal effect on Entodinium spp and Isotricha spp., and it has a good potential to change rumen fermentation by decreasing methane production, ammonia concentration and increasing the partitioning factor.