Table 1.

Effects of different doses of essential oils on gas and methane production, degradability of feeds, pH, and ammonia concentration in vitro^a

Essential oil and dose (g/liter)	Vol (ml)		Degradability (%)			Ammonia concn (mM)	pH
	Total gas	Methane	Apparent DM	NDF	True DM
Control, 0	59.8	26.1	68.7	33.9	72.2	28.4	5.47
CLO
0.25	54.4	23.2	66.2	30.8	71.0	31.3	5.49
0.50	57.0	21.5	66.3	31.9	71.4	23.3	5.52
1.00	49.3	17.1	63.7	27.0	69.6	20.0	5.56
SEM	1.25	0.88	0.44	1.46	0.91	1.84	0.006
Contrast	L,*** C**	L***	L,*** C*	NS	NS	L,*** C**	L***
EUO
0.25	59.8	25.4	69.8	36.7	73.3	27.9	5.46
0.50	57.5	24.0	68.2	32.8	71.8	27.1	5.48
1.00	53.6	21.5	66.4	27.2	69.6	27.8	5.52
SEM	0.75	0.74	0.46	2.13	0.81	2.27	0.005
Contrast	L***	L***	L,*** Q,* C*	NS	NS	NS	L,*** Q,** C**
GAO
0.25	56.8	20.1	69.8	37.0	73.4	26.2	5.49
0.50	57.1	18.7	69.1	36.9	73.4	27.7	5.51
1.00	53.5	14.9	68.0	33.0	71.9	27.7	5.54
SEM	0.72	0.91	0.41	1.32	0.51	2.19	0.005
Contrast	L,*** C*	L***	NS	NS	NS	NS	L***
ORO
0.25	53.0	22.8	65.5	27.4	69.7	24.7	5.51
0.50	45.8	16.0	63.9	25.1	68.8	18.6	5.58
1.00	12.3	3.4	62.1	25.2	68.8	10.8	6.04
SEM	1.54	1.04	0.27	1.68	0.65	3.14	0.012
Contrast	L,*** Q***	L***	L,*** Q***	L,*** Q**	L,*** Q**	L**	L,*** Q***
PEO
0.25	57.0	23.9	68.4	32.3	71.6	27.5	5.49
0.50	54.5	20.8	67.0	29.6	70.5	23.8	5.53
1.00	53.0	19.4	65.9	32.1	71.5	23.7	5.58
SEM	1.04	0.64	0.22	1.55	0.61	2.30	0.005
Contrast	L***	L,*** Q**	L,*** C**	NS	NS	NS	L***

^aData were analyzed using dose levels of 0, 0.25, 0.50, and 1.0 g/liter for each essential oil. CLO, clove oil; EUO, eucalyptus oil; GAO, garlic oil; ORO, origanum oil; PEO, peppermint oil; NS, not significant. Only significant (***, P ≤ 0.01; **, P ≤ 0.05; *, P ≤ 0.10) linear (L), quadratic (Q), and cubic (C) effects are shown.