Table 2.

Effects of different doses of essential oils on in vitro VFA production from fermentation of feeds incubated with rumen fluid from cattle^a

Essential oil and dose (g/liter)	Total VFA (mM)	Molar proportion of VFA (mol/100 mol)						A/P
		Acetate	Propionate	Isobutyrate	Butyrate	Isovalerate	Valerate
Control, 0	99.5	55.5	25.0	1.60	13.2	2.43	2.29	2.22
CLO
0.25	97.3	55.6	24.9	1.40	13.6	2.31	2.28	2.24
0.50	101.0	54.9	24.1	1.66	14.3	2.83	2.16	2.28
1.00	91.9	55.7	22.5	1.45	15.8	2.13	2.36	2.47
SEM	1.60	0.35	0.28	0.12	0.34	0.13	0.11	0.026
Contrast	L,*** Q,* C*	NS	L***	NS	L***	Q,** C**	NS	L,*** Q**
EUO
0.25	105.3	54.0	24.7	1.68	14.8	2.53	2.29	2.19
0.50	107.6	52.4	24.1	1.87	16.6	2.89	2.11	2.18
1.00	106.8	50.3	23.5	1.74	19.4	2.92	2.07	2.14
SEM	2.68	0.47	0.18	0.13	0.31	0.14	0.049	0.024
Contrast	L*	L***	L***	NS	L***	L**	L***	L**
GAO
0.25	106.3	52.8	25.3	1.88	14.6	3.06	2.34	2.09
0.50	100.8	53.0	25.3	1.76	14.6	2.89	2.38	2.10
1.00	101.3	50.7	26.0	1.68	16.7	2.89	2.07	1.96
SEM	2.40	0.61	0.20	0.13	0.33	0.20	0.088	0.035
Contrast	NS	L***	L***	NS	L***	NS	L*	L***
ORO
0.25	98.3	54.3	24.5	1.62	14.8	2.74	2.07	2.22
0.50	90.0	58.1	18.3	1.49	17.3	2.09	2.79	3.19
1.00	61.0	59.3	20.8	2.17	14.2	1.71	1.85	2.85
SEM	2.75	0.57	0.30	0.17	0.32	0.23	0.13	0.068
Contrast	L,*** Q***	L,*** C***	L,*** Q,*** C***	L**	L,** Q,*** C***	L**	L,* Q,*** C***	L,*** Q,*** C***
PEO
0.25	103.4	53.1	25.5	1.66	15.0	2.82	1.95	2.09
0.50	105.7	53.9	24.5	1.46	14.5	3.07	2.50	2.22
1.00	103.3	56.0	21.5	1.91	15.0	3.11	2.42	2.60
SEM	3.04	0.71	0.41	0.14	0.40	0.16	0.17	0.062
Contrast	NS	Q**	L,*** Q***	NS	L**	L***	C*	L** Q**

^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; A/P, acetate to propionate ratio; NS, not significant. Only significant (***, P ≤ 0.01; **, P ≤ 0.05; *, P ≤ 0.10) linear (L), quadratic (Q), and cubic (C) effects are shown.