Shahin Yadeghari - Department of Animal Sciences, Faculty of Agriculture, Bu-Ali Sina University, Hamedan, Iran
Mostafa Malecky - Department of Animal Sciences, Faculty of Agriculture, Bu-Ali Sina University, Hamedan, Iran
Mehdi Dehghan Banadaky - Department of Animal Sciences, College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran
Bahman Navidshad - Department of Animal Science, Faculty of Agriculture, University of Mohaghegh Ardabili, Ardabil, Iran

Four in vitro experiments (Exp.) were conducted to evaluate lavender essential oil (LEO) effects at ۰ (control), ۲۵۰ (low dose), ۵۰۰ (medium dose), ۷۵۰ and ۱۰۰۰ µL per L(high doses) of incubation medium on rumen gas production kinetics (Exp.۱), ruminal digestibility and fermentation (Exp.۲), methane production (Exp.۳) and rumen acidosis (Exp.۴). The asymptote of gas production (A) increased quadratically (p < ۰.۰۰۱), but the lag phase (L) increased(p = ۰.۰۰۳), and gas production rate (µ) decreased linearly (p = ۰.۰۳۱) with increasing dose of LEO. A linear and quadratic effect (p < ۰.۰۱)was observed for the gas produced after ۲۴ hr of incubation (GP۲۴). In vitro true dry matter degradability (IVTDMD) and in vitro true organic matter degradability (IVTOMD) both decreased linearly (p < ۰.۰۱), but microbial biomass (MB) and partitioning factor (PF) changed quadratically with increasing doses of LEO (p < ۰.۰۵). A cubic effect was observed for total volatile fatty acid (TVFA) and ammonia (NH۳) concentrations (p < ۰.۰۵). Acetate molar percentage decreased (p = ۰.۰۰۴), whereas those of butyrate and valerate increased linearly (p <۰.۰۵)with LEO dosage. The molar percentage of propionate increased by ۱۰.۶۰ and ۱۲.۰۰% at low and medium doses of LEO, respectively. Methane production decreased by ۱۱.۰۰ and ۴۴.۰۰ to ۶۰.۰۰% at medium and high doses of LEO (p < ۰.۰۵), respectively. Lavender essential oil decreased also ruminal pH at all included doses (p < ۰.۰۵), intensifying rumen acidosis. These results revealed a dose-dependent selective effect (stimulatory at low and medium, and inhibitory at high doses) of LEO on rumen fermentation.

In vitro gas production, Lavender essential oil, Methanogenesis, Rumen, Volatile fatty acids