effect of some plant essential oils on in vitro ruminal methane production and on fermentation characteristics of a mid-forage diet

the objective of the present study was to investigate the effect of different doses of some 7 natural semi-arid medicinal plants’ essential oils on in vitro ruminal digestion and fermentation patterns of a mid-forage (alfalfa hay: concentrates, 1:1) diet. treatments consisted of either basal diet alone (control) or added with 35, 70, 140 or 280 µl l-1 of coriander, oregano, caraway, cumin, cinnamon, pistachio hull and thyme essential oils, incubated for 24 hours at 38.7ºc. the essential oils of cinnamon and pistachio applied as 280 µl l-1 and thyme applied at 140 and 280 µl l-1 caused a decrease in dm disappearance as compared with control. thyme and pistachio essential oils (used at 280 µl l-1) resulted in a decrease of ndf disappearance, while caraway (70 µl l-1) and cumin (140 µl l-1) resulted in an increase in it (14.8% and +18.2%, respectively). relative to control, the essential oils applied, did not significantly affect the medium n-nh3 concentration (except thyme at 140 and 280 µl l-1), ph (except thyme and cumin essential oils, 6.41 and 6.22 vs. 6.3, respectively), gas produced (except thyme at 280 µl l-1) and feed fermentation efficiency (ffe). relative to control, addition of all the essential oils resulted in a decrease of cp disappearance and ch4 (except for cumin) production as mm-1 incubated. findings revealed that these essential oils may allow manipulation of rumen microbial fermentation.