Evaluating the effects of essential oils on methane production and fermentation under in vitro conditions

Figures & data

Table 1. The effect of different essential oil addition (500 mg/L) to rumen cultures on gasses production (ml).

	Gas production, ml
Essential oil	Total	CH4	CO2	H2
Control	175.90^a	22.19^a	138.37^a	0.08^b
Anise oil	137.41^ab	14.89^b	106.77^bc	0.14^a
Clove oil	149.07^ab	13.77^b	95.42^bc	0.09^b
White thyme oil	89.37^c	5.19^c	63.92^c	0.15^a
Citronella oil	174.15^a	19.95^a	125.55^ab	0.06^b
SEM	17.416	2.044	14.248	0.561
p Value	.03	.01	.03	.01

CH₄: methane; CO₂: carbon dioxide; H₂: hydrogen; SEM: standard error mean.

^a,b,cColumns with different superscripts are statistically different at p < .05.

Table 2. Effect of clove oil (CLO) dose level on gasses production and fermentation parameters.

		Treatments, mg/L
Item	CON	125	250	500	SEM	p Value
pH	6.15^a	6.01^ab	5.75^c	5.89^bc	0.057	.01
Gas production, ml
Total	168.88^a	156.01^a	142.99^b	129.59^c	4.875	.01
CH4	27.07^a	22.87^b	22.07^bc	18.96^c	1.519	.03
CO2	120.7^a	108.46^ab	97.49^bc	89.20^c	4.667	.01
H2	0.08	0.07	0.05	0.07	0.012	.46
NH3-N, mg/dL	26.48	26.40	26.57	26.77	0.246	.53
Total VFA, mM	88.13	75.74	74.06	70.99	7.774	.23
VFA, mole/100 mole
Acetate	46.58	40.88	41.32	44.46	3.686	.43
Propionate	30.72	33.72	33.22	30.85	1.872	.33
Butyrate	16.35	18.20	18.02	17.63	1.470	.62
Iso-butyrate	1.30	1.54	1.55	1.34	0.361	.85
Valerate	2.26	2.50	2.52	2.45	0.204	.59
Iso-valerate	2.77	3.16	3.37	3.27	0.288	.28
Acetate/propionate	1.55	1.24	1.30	1.44	0.203	.46

VFA: volatile fatty acids; NH3-N: ammonia N; CH₄: methane; CO₂: carbon dioxide; H₂: hydrogen; SEM: standard error mean; CON: control.

^a,b,cRows with different superscripts are statistically different at p ≤ .05.

Table 3. Effect of white thyme oil (WTO) dose level on gasses production and fermentation parameters.

		Treatments, mg/L
Item	CON	125	250	500	SEM	p Value
pH	6.48	6.49	6.48	6.46	0.021	.64
Gas production, ml
Total	163.40^a	159.78^a	147.63^b	78.94c	4.160	.01
CH4	22.79^a	21.82^a	21.13^a	4.97b	0.865	.01
CO2	118.10^a	111.15^ab	105.10^b	55.82^c	3.041	.01
H2	0.07	0.05	0.11	0.16	0.039	.11
NH3-N, mg/dL	27.88^a	27.85^a	26.97^a	21.50^b	0.636	.01
Total VFA, mM	87.51^a	68.25^b	54.64^b	54.10^b	6.771	.01
VFA, mole/100 mole
Acetate	46.92	36.53	43.24	42.24	3.948	.17
Propionate	27.45	33.26	32.93	32.47	2.316	.13
Butyrate	18.10^ab	20.63^a	15.22^b	17.90^ab	1.319	.04
Iso-butyrate	1.42^b	1.92^a	1.54^b	1.58^ab	0.143	.05
Valerate	2.91^ab	3.77^a	3.51^a	2.27^b	0.366	.02
Iso-valerate	3.21	3.90	3.56	3.55	0.209	.08
Acetate/propionate	1.77	1.15	1.32	1.30	0.251	.18

VFA: volatile fatty acids; NH3-N: ammonia N; CH₄: methane; CO₂: carbon dioxide; H₂: hydrogen; SEM: standard error mean; CON: control.

^a,b,cRows with different superscripts are statistically different at p ≤ .05.

Table 4. Effect of anise oil (ANO) dose level on gasses production and fermentation parameters.

		Treatments, mg/L
Item	CON	125	250	500	SEM	p Value
pH	6.14^c	6.15^c	6.17^b	6.21^a	0.003	.01
Gas production, ml
Total	149.06^a	147.47^a	130.42^b	123.51^b	6.457	.02
CH4	20.77^a	20.30^a	17.31^b	16.53^b	1.183	.03
CO2	110.8^a	107.80^ab	94.91^bc	90.35^c	5.642	.03
H2	0.07^ab	0.06^b	0.05^b	0.09^a	0.010	.04
NH3-N, mg/dL	26.01^b	26.80^a	26.89^a	25.67^b	0.228	.01
Total VFA, mM	75.11^b	81.51^b	97.13^a	47.74^c	4.482	.02
VFA, mole/100 mole
Acetate	39.91^b	45.86^ab	52.88^a	43.16^b	3.237	.03
Propionate	32.61^ab	29.99^bc	26.05^c	35.31^a	1.881	.01
Butyrate	19.85^a	16.39^b	14.04^b	14.16^b	1.050	.01
Iso-butyrate	1.52	1.96	1.57	1.38	0.183	.08
Valerate	2.78	2.54	2.33	2.46	0.146	.10
Iso-valerate	3.33	3.25	3.13	3.53	0.133	.11
Acetate/propionate	1.25^b	1.54^b	2.03^a	1.23^b	0.180	.01

VFA: volatile fatty acids; NH₃-N: ammonia N; CH₄: methane; CO₂: carbon dioxide; H₂: hydrogen; SEM; standard error mean; CON: control.

^a,b,cRows with different superscripts are statistically different at p ≤ .05.

Table 5. Effect of essential oils on dry matter and neutral detergent fibre digestibility.

		Treatments
Item	CON	ANO	WTO	CLO	SEM	p Value
Digestibility, %
Dry matter	56.29^a	52.20^b	48.44^c	50.76^b	1.594	.01
Neutral detergent fibre	53.05	51.91	53.59	51.46	1.854	.41

CON: control; ANO: anise oil; WTO: white thyme oil; CLO: clove oil.

^a,b,cRows with different superscripts are statistically different at p ≤ .05.