1768
OPTIMAL RATIO OF COMBINED ORIGANUM ESSENTIAL OILS TO REDUCE METHANE EMISSIONS UNDER IN VITRO RUMINAL FERMENTATION
Keywords: thymol, carvacrol, methane
Origanum (Origanum vulgare) essential oils (EO; thymol T and carvacol C) have been reported as potential anti-methanogenic additives for dairy cattle rations. An in vitro fermentation trial was conducted to determine the optimal T:C ratio (100:0, 80:20, 60:40, 40:60, 80:20 and 0:100) in an EO combined dose of 100 mg/L added to a total mixed ration (TMR; 65:35 concentrate:forage). The incubation was carried out in 60 mL flasks in triplicate for each T:C ratio and the control. The in vitro buffered solution was prepared anaerobically. Inside of anaerobic chamber 20 mL of buffered medium and 10 mL of rumen fluid were dispensed in each flask containing 200 mg of the ground substrate. The flasks were sealed with butyl rubbers and aluminum seals and incubated at 39 ºC for 24 h with a constant shaking at 150 rpm. After 24h of incubation, gas production was recorded and sampled to determine its composition and 5mL of liquid content were taken from each flask and preserve with metaphosphoric acid to determine VFA. Gas composition and VFA concentration were determined by chromatography. Dry matter digestibility (IVDMD) was determined by the DAISY procedure. Data were analyzed by PROC GLM of SAS (SAS, 1992) by a complete randomized design considering the EO ratio as sole effect. Adding EO to the ration did reduce total gas production (P<0.0001) in all C:T ratios (Table 1). Also, methane production was decreased (P<0.05) by the EO in all treatments. However, the 80:20 T:C ratio showed the greatest reduction (P<0.0001). Total VFA concentration and IVDMA was not affected (P>0.70 and 0.93, respectively) by EO addition. The molar proportion of acetate was decreased by the 60:40 T:C ratio. These results suggest that 80:20 T:C ratio has the best potential to decrease methane emissions of dairy cattle without DM digestibility decreases.
Treatment (T:C ratio) |
GAS (ml/200 mg DM) |
Reduction (%) |
Methane (ml/200 mg DM) |
Reduction (%) |
Control |
36 |
-- |
7.55 |
-- |
100:0 |
32 |
11 |
6.48 |
14 |
80:20 |
28 |
22 |
5.84 |
23 |
60:40 |
32 |
11 |
6.73 |
11 |
40:60 |
35 |
3 |
7.29 |
3 |
20:80 |
30 |
17 |
6.40 |
15 |
0:100 |
32 |
11 |
6.51 |
14 |