Impact of geranium essential oil as a sustainable feed additive on in vitro rumen gas and methane production, nutrient degradability and fermentation efficiency Cover

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Impact of geranium essential oil as a sustainable feed additive on in vitro rumen gas and methane production, nutrient degradability and fermentation efficiency

Annals of Animal Science

By: Ahmed E. Kholif, Moyòsore J. Adegbeye, Gouda A. Gouda, Tarek A. Morsy and Einar Vargas-Bello-Pérez

Open Access

|Feb 2026

Figures & Tables

In vitro ruminal gas production (mL/g incubated DM) of a total mixed ration supplemented with different levels of geranium oil

In vitro ruminal methane (CH4) production (mL/g incubated DM) of a total mixed ration supplemented with different levels of geranium oil

In vitro ruminal carbon dioxide (CO2) production (mL/g incubated DM) of a total mixed ration supplemented with different levels of geranium oil

Chemical composition of ingredients incubated diet (g/kg DM)_

	CFM¹	Berseem hay	Rice straw	Diet²
Dry matter	903	890	940	902
Organic matter	923	884	851	900
Crude protein	165	128	42	138
Ether extract	47	54	19	47
Nonfibrous carbohydrates	414	224	166	313
Neutral detergent fiber	297	478	624	402
Acid detergent fiber	175	381	394	279
Metabolizable energy (Mcal/kg DM)³	3.60	2.65	1.98	3.06

In vitro rumen gas production (GP), methane (CH4) and carbon dioxide (CO2) kinetics as affected by increasing levels of geranium oil (%, dry matter basis)

	GP parameters¹			CH₄ parameters²				CO₂ parameters³
Level	A	C	Lag	A	c	Lag	%⁴	A	c	Lag	%⁴
0	78^c	0.076^a	1.55	28.6^b	0.035	1.42	29.3^a	58.8^c	0.036^c	2.47	63.5
0.5	108^b	0.084^a	1.62	35.6^b	0.036	1.56	27.5^ab	75.0^b	0.045^b	2.37	62.5
1	116^b	0.078^a	1.56	36.5^b	0.042	1.54	27.9^ab	79.1^b	0.048^ab	2.18	62.7
1.5	132^a	0.060^b	1.65	38.9^a	0.035	1.56	25.4^b	88.3^a	0.053^a	2.35	65.5
SEM	2.0	0.0020	0.09	1.05	0.0037	0.061	0.77	1.65	0.0017	0.241	1.28
P value
Treatment	<0.001	0.001	0.852	0.007	0.519	0.356	0.045	<0.001	0.008	0.859	0.392
Linear	<0.001	0.563	0.962	0.007	0.212	0.193	0.231	<0.001	0.002	0.420	0.683
Quadratic	<0.001	0.044	0.425	0.002	0.460	0.228	0.025	<0.001	0.004	0.883	0.493

Volatile compounds in geranium oil (Pelargonium graveolens L_) identified by GC-MS analysis

Compound¹	RT²	Concentration³ (%)
α-Pinene	5.19	1.1
Myrcene	7.94	0.5
Linalool	10.18	7.9
Menthone	10.99	2.0
Isomenthone	12.89	8.3
α-Terpineol	13.86	1.1
Citronellol	15.41	32.4
Trans-Geraniol	16.55	13.3
Citronellyl formate	17.21	15.4
Geranyl formate	18.39	3.4
β-Caryophyllene	23.20	1.8
Isoledene	24.07	4.0
Muurolene	25.56	1.7
Guaia-6,9-diene	27.29	0.8
Phenylethyltiglate	29.62	1.4
Eudesmol	30.84	4.9

In vitro rumen fermentation profile of diet with increasing levels of geranium oil (%, dry matter basis)

	Degradability¹			SCFAs²								Fermentation3
Level	dDM	dNDF	dADF	Total	C2	C2 (%)	C3	C2 (%)	C2: C3	C4	C2 (%)	pH	NH3-N	ME	PF24	MCP	GY24
0	473^c	439^b	412^c	23.4^c	11.4^c	48.9	7.90^b	33.7	1.47	4.08	17.4	6.27^b	10.4	4.68^b	6.22^a	328	139^b
0.5	511^bc	489^ab	463bc	27.4^b	13.7b	50.0	9.25^a	33.8	1.48	4.42	16.1	6.60^a	10.6	5.31^a	4.83^b	306	183^a
1	536^ab	510^a	492ab	27.3^b	13.9b	51.1	9.80^a	35.9	1.42	3.54	12.9	6.53^a	10.7	5.44^a	4.74^b	321	183^a
1.5	574a	539^a	524a	30.5^a	15.8a	52.0	9.80^a	32.1	1.62	4.84	15.8	6.50^ab	10.8	5.50^a	4.63^b	354	175^a
SEM	11.0	12.0	12.3	0.34	0.40	2.00	0.292	1.21	0.100	0.517	1.73	0.055	0.28	0.046	0.151	12.5	5.3
P value
Treatment	0.001	0.002	0.001	<0.001	0.004	0.716	0.005	0.258	0.577	0.395	0.376	0.013	0.804	<0.001	0.002	0.126	0.001
Linear	0.003	0.003	0.002	<0.001	0.002	0.446	0.002	0.239	0.732	0.487	0.106	0.009	0.468	<0.001	0.001	0.679	0.004
Quadratic	0.008	0.011	0.010	<0.001	0.008	0.624	0.049	0.168	0.345	0.151	0.649	0.027	0.645	<0.001	0.001	0.689	0.009

DOI: https://doi.org/10.2478/aoas-2025-0118 | Journal eISSN: 2300-8733 | Journal ISSN: 1642-3402

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Language: English

Submitted on: Apr 1, 2025

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Accepted on: Oct 20, 2025

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Published on: Feb 16, 2026

Published by: National Research Institute of Animal Production

In partnership with: Paradigm Publishing Services

Publication frequency: Volume open

Keywords:

geranium essential oil,

in vitro fermentation,

Related subjects:

Veterinary medicine

© 2026 Ahmed E. Kholif, Moyòsore J. Adegbeye, Gouda A. Gouda, Tarek A. Morsy, Einar Vargas-Bello-Pérez, published by National Research Institute of Animal Production
This work is licensed under the Creative Commons Attribution 3.0 License.