| Livestock Research for Rural Development 37 (4) 2025 | LRRD Search | LRRD Misssion | Guide for preparation of papers | LRRD Newsletter | Citation of this paper |
Methanogenesis is a physiological process in ruminants which has negative impact on nutrient utilization and environmental safety. Thus, this research was conducted to evaluate the effect of lemongrass as additive in tropical grass-based substrate for abating methane emission under in vitro experiment. Lemongrass powder was included at increasing levels of 0, 5, 10 and 15 mg/g of substrate dry matter. The substrate consisted of 70% Megathyrsus maximus and 30% concentrate supplement on dry matter basis. In vitro gas production was measured over a period of 48 hours under anaerobic conditions at 39oC following standard procedures. Total gas production, substrate degradation and percentage methane production were determined. Results showed that the net gas production, substrate degradation and percentage of methane production decreased (p<0.05) with the inclusion of lemongrass above 5 mg/g of substrate dry matter. The least methane production was obtained at the highest inclusion level of 15 mg/g resulting to about 31.4% methane reduction. The highest supplementation level similarly showed the highest reduction effect on the in vitro substrate dry matter degradation. It can be concluded that lemongrass supplementation above 5 mg/g dry matter in tropical grass-based diet can potentially serve as an antimethanogenic additive to manipulate ruminal fermentation patterns away from methanogenesis through inhibition of substrate degradation.
Keywords: phytogenics, rumen fermentation efficiency, methane emission, fibrous feed
Rumen microbial fermentation yields methane as an end product which equates to an energy loss when estimating energy metabolism in livestock feeding systems and this translates to a reduction in feed utilization efficiency (Morgavi et al 2023). It is estimated that up to 12% of dietary gross energy, and between 8 to 14% of digestible energy intake, which would have been beneficial for ruminants’ productive performance, is often lost as a result of enteric methane emission (Min et al 2022; Lileikis et al 2023). Particularly, enteric methane emission has been reported to be high with tropical grasses which are fibrous in nature (Archimede et al 2011; Ku-vera et al 2020). Asides from the resultant feed energy losses, methane production from ruminants is also associated with environmental degradation (Thacharodi et al 2024; Wang et al 2025). According to Arndt et al (2022), about 88% of global greenhouse gas emissions is contributed by enteric fermentation in ruminants. Tseten et al (2022) reported that 35% of the total methane emissions emanating from the livestock sector comes from beef cattle production, 30% from dairy cattle and 15% is attributed to small ruminants and buffalos. Strategies for reducing enteric methane production from ruminants are therefore necessary for improving feed energy utilization, ruminant productivity and environmental sustainability.
Herbal plants have been reported with the potential for mitigating rumen methane emission due to the presence of bioactive compounds such as tannin, flavonoids, and saponin which exhibit antimicrobial properties (Antonius et al 2023). With the vast array of tropical herbs containing plant secondary metabolites, and the advocacy for sustainable ruminant production, there is need for continuous evaluation of these plants as natural feed additives for controlling rumen fermentation away from methanogenesis. Lemongrass is an aromatic herb belonging to the Gramineae family and it is known to contain diverse bioactive compounds including polyphenols, flavonoids, alkaloids, terpenoids, saponins, and tannins (Kiani et al 2022; Tazi et al 2024). Till date the effect of lemongrass as feed additive for controlling enteric methane in tropical grass-based diets for ruminants has not been extensively documented. This study therefore, evaluated the potentials of lemongrass (Cymbopogon citratus) as an antimethanogenic herbal additive in a tropical grass-based diet using the in vitro gas production technique. The in vitro gas production method provides a cost-effective, fast and reliable method for feed evaluation (Getachew et al 2004). This evaluation method has been used for various purposes including the testing of plants and their extracts as additives for controlling rumen methanogenesis (Durmic et al 2014; Bunglavan et al 2010; Aderinboye et al 2020; Hodge et al 2025).
This study was carried out at the Analytical laboratory of the Animal Science Department, Federal University of Agriculture, Abeokuta, Nigeria. The area is located in the southwestern part of Nigeria on coordinates 7o13′58″ N and 3o26′14″ E (Google Earth, 2025).
Lemongrass was harvested from areas within Abeokuta, Ogun State, Nigeria during the late rainy season. The leaves were harvested at ground level, chopped into small lengths of about 2 cm and then air-dried in a well ventilated room until suitable for milling. The dried samples were ground through a 1 mm sieve and stored in air-tight plastic bags for subsequent use for phytochemical analysis and in vitro gas production study.
The feed samples (Table 1) used as substrate in this study consisted of 70% Megathyrsus maximus grass and 30% concentrate on dry matter basis. The concentrate contained 48% wheat offal, 32% brewers’ dried grain, 17% Maize, 2% bonemeal and 1% common salt. The lemongrass powder was added as a phytogenic additive at four different levels of 0, 5, 10 and 15 mg/g of the substrate dry matter to make four treatments in a completely randomized design.
The in vitro gas production measurement was done following the procedure of Menke and Steingass (1988). Rumen fluid was collected from the rumen of three West African dwarf goats which were previously fed on a grass and concentrate diet. The rumen fluid was collected in the morning before feeding using an orogastric tube into a flask pre-warmed to 39ºC. This was then immediately transported to the laboratory and strained through a four-layered cheese cloth into a container and kept incubated at 39ºC. The strained rumen fluid was then mixed with a mineral-buffer solution (1:2 v/v) to constitute the inoculum used for digestion.
About 200 mg of the substrate was weighed into dacron bags (2mm by 5mm size) of known weights and inserted into 100 ml glass syringes. The pistons were greased using vaseline and fitted into the syringes. The syringes were then filled with 30 ml inoculum. The piston of each syringe was pushed upwards to eliminate air completely in the syringe. A silicon tube inserted at the tip of the syringe was tightened by a metal clip to prevent escape of gas during the incubation process. Incubation was carried out at 39oC and the volume of gas produced was measured at three hours (h) interval from 0 to 48 hours. Three blank syringes containing 30 ml of inoculum only were included in the run to correct for gas production from fermentation of residual feed particles in rumen fluid. The average volume of gas produced from the blanks was deducted from the volume of gas measured at the corresponding incubation hour to obtain the net gas production.
Methane production was determined at the end of the final gas readings using the carbon-dioxide absorption method with sodium hydroxide as the alkaline solution for trapping carbon-dioxide, following the procedure described by Fievez et al (2005). The bags containing the residue after incubation were recovered from each of the syringes. The bags were washed properly under continuous flow of water to terminate fermentation. The bags were then air-dried to reduce moisture and thereafter oven-dried at 65oC to a constant weight. The bag with the residue for each sample was weighed and the weight of residue was estimated by subtracting the known weight of bag from the total weight of the bag and residue. The in vitro dry matter degradability was then determined by subtracting the quantity of residue from the quantity of substrate incubated and multiplying by 100%.
Proximate composition of Megathyrsus maximus and concentrate were done according to the procedure of AOAC (2000) while the fibre fractions were determined according to Van Soest et al (1991). Phytochemical composition of lemongrass powder was determined quantitatively following standard procedures.
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Table 1. Nutrient composition (% DM) of feed substrate |
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Nutrient content |
Megathyrsus maximus (tropical grass) |
Concentrate |
|
|
Crude protein |
10.7 |
18.1 |
|
|
Organic matter |
89.8 |
93.9 |
|
|
Neutral detergent fibre |
68.4 |
53.9 |
|
|
Acid detergent fibre |
30.6 |
22.5 |
|
|
Acid detergent lignin |
18.1 |
10.7 |
|
Data generated from this study were analyzed using one-way analysis of variance procedure of SAS (2002). Significant differences between treatment means were separated using the Duncan multiple range test (SAS 2002).
The quantitative evaluation of the phytochemical content of lemongrass leaves showed the presence of some plant secondary compounds (Figure 1) which have been associated with antimicrobial activities (Othman et al 2019; Huang et al 2024; Yan et al 2024). The consideration for the use of plants as alternative antibiotic agents, is primarily based on the presence of these plant secondary compounds. The antimicrobial properties of plants and their extracts are often dependent on the concentration and interactions of these secondary metabolites (Asfaw et al 2023).
The inclusion levels of lemongrass additive resulted in a reduction in total gas production and substrate dry matter degradation relative to the control with a high correlation observed (Table 2; Figures 2 and 3). A diverse community of microorganisms degrade feed in the rumen to produce fermentation gases along with other end-products such as volatile fatty acids and microbial proteins (Dong et al 2023; Palmonari et al 2024). Thus, the concomitant reduction in total gas production and substrate dry matter degradation in response to lemongrass additive, suggests that microbial fermentation activity was inhibited. Reductions in total gas production have been reported by several authors with the use of plants containing tannin, alkaloid and flavonoid (Cardoso-Gutierrez et al 2021; de Jesus Pereira et al 2017; Gemeda and Hassan 2015; Kim et al 2015). Similarly, there was a reduction (P < 0.05) in methane production with lemongrass inclusion above 5 mg/g (Table 2; Figure 4). Methane reduction with lemongrass additive was assumed to be caused by the antimicrobial effect of alkaloids, tannin, flavonoid and other phytochemical compounds in lemongrass. The ability of herbal plants to reduce methane production has been associated with the rich content of phytochemicals and enteric methane reductions of between 8 - 50% have been reported (Lambo et al 2024). Methane reduction percentage of 31.4% was observed in this study with the inclusion of 15 mg/g of lemongrass powder. A similar methane reduction of up to 30% was reported by Cardoso-Gutierrez et al (2021) with the use of tannin from tropical plants. Some of the established mechanisms of action by which plant secondary metabolites exert antimicrobial effects includes cell membrane disruption, enzyme inhibition, substrate deprivation, and prevention of bacterial colonization (Reddy et al 2020). Methane is produced by methanogenic archaea which utilize carbon dioxide and hydrogen produced from rumen fermentation as substrate for methanogenesis (Choudhury et al 2022). It was possible that methanogens responsible for methanogenesis were inhibited through substrate deprivation. However, in this study, the mechanism for methane reduction was assumed to be through reduction of substrate dry matter degradation which suggested a possible inhibition of bacteria colonization in agreement with Reddy et al (2020).
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| Figure 1. Phytochemical composition of lemongrass powder |
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Table 2. Effect of lemongrass on total gas production, dry matter degradation and methane production from microbial fermentation of tropical grass-based substrate in an in vitro medium |
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|
Lemongrass inclusion in substrate, mg/g |
SEM |
p |
||||||
|
0 |
5 |
10 |
15 |
|||||
|
Total gas production, ml |
21.9a |
18.3b |
16.8c |
16.4c |
0.69 |
0.006 |
||
|
Substrate degraded, % |
53.4a |
48.2b |
42.4c |
41.0c |
1.41 |
<0.001 |
||
|
Methane, % |
36.6a |
34.6a |
29.9b |
25.1c |
1.41 |
<0.001 |
||
|
abc Means in the same row without common letters are different at P<0.05; Lemongrass was included in the substrate at 0, 5, 10 and 15 mg/g dry matter of substrate incubated |
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 |
| Figure 2. Curvilinear trend between gas production and
inclusion levels of lemongrass in tropical grass-based substrate degraded in vitro |
 |
| Figure 3. Curvilinear trend between methane production and
inclusion levels of lemongrass in tropical grass-based substrate fermented in vitro |
 |
| Figure 4. Curvilinear trend between methane production and inclusion levels of lemongrass in tropical grass-based substrate fermented in vitro |
The addition of lemongrass above 5 mg/g in tropical grass-based substrate resulted in lower percentage of methane production. Therefore, lemongrass can be an effective antimethanogenic additive for modulating rumen fermentation in ways that would promote sustainable ruminant production in a tropical grass-based feeding system. The reduction effect on substrate degradation however, needs further investigation with in vivo studies to evaluate animal response.
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