Feed herbs or plant extracts
System: Beef Cattle
Applicability
Mainly applicable for: Zero- or low-grazing systems; animals in fattening and finishing phase, or lactating.
Not or less applicable for: Full grazed system, young suckling animals, animals that do not receive supplementation
Description
Feeding specific herbs or plant extracts that reduce methane synthesis, in order to reduce the enteric methane emissions from the rumen and/or intestinal fermentation. Regarding herbs and legumes, various species (e.g. chicory, plantain, biserrula) are being investigated but efficacy and animal response vary considerably. Regarding plant extracts, tannins, saponins and essential oils are secondary plant metabolites that have been demonstrated to be able to enteric methane emission and in some cases enhance feed intake.
Mechanism of effect
Plant extracts can influence the microbial ecosystem in the rumen, inhibit certain microbial groups and protozoa, and reduce protein degradation in the rumen indirectly reducing hydrogen availability for methanogenesis.
Essential oils can disrupt cell membranes in some rumen microbes, selectively reducing populations of bacteria that produce methane.
Tannins and saponins can also cause a shift in microbial population, promoting other microorganisms that produce less methane. Saponins may enhance the digestibility and utilization of nutrients, which could lead to better feed efficiency and reduced methane production per unit of feed consumed.
Herbs may also exert their effect on methane through specific compounds, similar to plant extracts, or by their degradation characteristics. Content of compounds as well as degradation characteristics may vary substantially with growth stage and therefore also variable effects on methane can be expected. An optimum dosage of plant extracts is required to prevent negatively impacts on fibre digestibility and feed intake. The optimum dosage of plant extracts or inclusion rates of herbs is expected to differ from dairy, and also will differ with intensity of feeding and type of beef production.
Effects on GHG emissions
Reference situation: Not feeding herbs or plant extracts
Effect on total greenhouse gas (GHG) emissions
| Mean effect and range in kg CO2-equivalents | per kg product | per farm | |||
| Mean | Min-Max | Mean | Min-Max | Level of evidence | |
| Essential oils | ● | o-● | ● | o-● | Medium |
| Tannin | ● | ● – ●● | ● | ●–●● | Medium |
Legend
| ● – Small effect (<5%) | o – No effect | ? – Effect unknown |
| ●● – Medium effect (5-20%) | ● – Unfavourable effect | |
| ●●● – Large effect (>20%) | ● – ● – Variable effect (depending on farm characteristics or way/level of implementation) | |
Effect per emission source
| Mean effect on absolute emission from | Animal | Manure storage | Feed and forage production | Barn | |||
| CH4 | CH4 | N2O | CO2 | N2O | LUC | CO2 | |
| Tannin (extract) | ●● | ● | |||||
| Essential oils | ●● | ● | |||||
*risk of an adverse effect (see ’cause of variable or unfavourable effect’)
Legend
| ● – Small effect (<5%) | o – No effect | ? – Effect unknown |
| ●● – Medium effect (5-20%) | ● – Unfavourable effect | |
| ●●● – Large effect (>20%) | ● – ● – Variable effect (depending on farm characteristics or way/level of implementation) | |
Cause of variable or unfavourable effect
Essential oils
The effect depends on the type of oil or blend, the dietary composition, type of forage (e.g., corn silage vs. alfalfa silage), animal characteristics, feed intake level, inclusion dosage and duration, animal type, duration of treatment. The level of evidence differs per type of oil and blend. The expected effect is moderate and it is typically applied in total mixed rations (TMR) and longer application period. The reduction effect in dairy cattle is more consistent than beef.
Tannin
The effect depends on the dietary composition, inclusion dosage level (although the high dosage level might be rejected by cow) and duration, type of forage (e.g., corn silage vs. alfalfa silage), Type of Tannin (hydrolysable tannins and condensed tannins), animal characteristics, feed intake level, supplementation method (e.g., as part of feed or as a separate supplement). The expected effect is moderate and it is typically applied in total mixed rations (TMR) and longer application period. Higher effect for tannin can be expected in case of combination with mimosine or saponins, and high dosage.
| Literature references | Essential oils |
|---|---|
| Castro-Montoya et al., 2015 | In vivo and in vitro effects of a blend of essential oils on rumen methane mitigation |
| Batley et al., 2024 | The essential oil blend Agolin Ruminant L reduces methane production in vitro and in vivo when included in the drinking water of cattle |
| Literature references | Tannin |
|---|---|
| de Souza Congio et al., 2021 | Enteric methane mitigation strategies for ruminant livestock systems in the Latin America and Caribbean region: A meta-analysis |
| Aboagye et al., 2018 | Effects of hydrolyzable tannin with or without condensed tannin on methane emissions, nitrogen use, and performance of beef cattle fed a high-forage diet |
| Nayak et al., 2015 | Management opportunities to mitigate greenhouse gas emissions from Chinese agriculture |