The objective of the present study was to evaluate the in vitro effect of medicinal plants or spices powder on ruminal methane and total gas production. In vitro incubation was carried out based gas production method. Approximately 300 mg of dried alfalfa hay (as control) (NDF= 537 and CP= 150 g/kg DM) or plus 12 mg of garlic, cinnamon, cumin, nutmeg or rosemary powder as treatments were placed in a 100 ml glass syringes (n= 3) containing 40 ml of buffered rumen fluid (ratio of buffer to rumen fluid was 2:1), and incubated for 24 h at 38.5 ºC. Rumen fluid was obtained from three adult ruminally fistulated sheep (49.5 ± 2.5 kg body weight), before the morning feeding, and immediately strained through four layers of cheesecloth. After 24 h of incubation, gas which was accumulated in the headspace of each syringe was measured, and a sample of the gas was collected into a 10 ml vacuum tube. Methane content of the produced gas was determined using gas chromatography procedure (GC, Sri 8610, and Column: 6% cyanopropylphenyl, 94% dimethylpolysiloxane). Volumes of gas and methane (ml) were converted to mmol assuming one mol is equivalent to 22.4l L of gas (Table1). Data were statistically analyzed using SAS (V. 9/1) and Duncan test was used to compare the means (P< 0.05). The results of the present study indicated that all medicinal herbs or spices, expect Nutmeg, reduced significantly (P< 0.05) in vitro methane and total gas production from alfalfa hay compared with the control. These finding confirmed the ability of Rosemary to decrease methane production, which may help to improve the efficiency of energy used in the rumen.
