Feed herbs or plant extracts
System: Dairy Cattle
Applicability
Mainly applicable for: TMR systems, zero- or low-grazing systems
Not or less applicable for: More difficult to control in extensive and grazing systems (but possible)
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 negative impacts on fibre digestibility and feed intake.
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 | |
| Tannin (extract) | ● | ● – ●● | ● | ●–●● | Medium |
| Essential oils | ● | o – ● | ● | o-● | Low |
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.
Other Effects
Effects on yield and cost-effectiveness
| Yield | Labor | Costs and revenues | ||||
|---|---|---|---|---|---|---|
| Animals | Crops | Time | Capital investment | Operational Costs | Revenues | |
| Essential oils | o | o | ●–● | o | ● | o-● |
| Tannin | ●-o | o | ●–● | o | ● | ●–● |
Legend (thresholds differ per indictor and can be found in the tooltip)
| ● – Small favorable effect | o – No effect | ? – Effect unknown |
| ●● – Medium favorable effect | ● – Unfavourable effect | |
| ●●● – Large favorable effect | ● – ● -Variable effect (depending on farm characteristics or way/level of implementation) | |
Effects on other sustainability aspects
| Risks of trade-offs | Potential synergies | |
|---|---|---|
| Essential oils | Ammonia emission | |
| Tannin | Ammonia emission |
| Literature references | Essential oils |
|---|---|
| Carrazco et al. 2020 | The Impact of Essential Oil Feed Supplementation on Enteric Gas Emissions and Production Parameters from Dairy Cattle |
| Castro-Montoya et al., 2015 | In vivo and in vitro effects of a blend of essential oils on rumen methane mitigation |
| Klop et al., 2017 | Enteric methane production in lactating dairy cows with continuous feeding of essential oils or rotational feeding of essential oils and lauric acid |
| Hart et al., 2019 | An Essential Oil Blend Decreases Methane Emissions and Increases Milk Yield in Dairy Cows |
| Belanche et al., 2020 | A Meta-analysis Describing the Effects of the Essential oils Blend Agolin Ruminant on Performance, Rumen Fermentation and Methane Emissions in Dairy Cows |
| Van Gastelen et al., 2024 | Effect of a blend of cinnamaldehyde, eugenol, and Capsicum oleoresin on methane emission and lactation performance of Holstein-Friesian dairy cows |
| Literature references | Tannin |
|---|---|
| Montoya-Flores et al., 2020 | Effect of Dried Leaves of Leucaena leucocephala on Rumen Fermentation, Rumen Microbial Population, and Enteric Methane Production in Crossbred Heifers |
| de Souza Congio et al., 2021 | Enteric methane mitigation strategies for ruminant livestock systems in the Latin America and Caribbean region: A meta-analysis |
| Nayak et al., 2015 | Management opportunities to mitigate greenhouse gas emissions from Chinese agriculture |
| Literature references | Herbs |
|---|---|
| Badgery et al., 2023 | Reducing enteric methane of ruminants in Australian grazing systems – a review of the role for temperate legumes and herbs |