Sheep- Feed herbs or plant extracts

Feed herbs or plant extracts

System: Sheep

Applicability

Mainly applicable for: Feedlot or finishing systems (zero-grazing).

Not or less applicable for: Extensive (traditional) grazing systems/pastoral systems

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 responses vary considerably. Regarding plant extracts, tannins, saponins and essential oils are secondary plant metabolites that have been demonstrated to reduce emissions.

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 beef, and in general also the efficacy that can be achieved differs between ruminant types.

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	●	● – ●●	●	●–●●	Medium
Saponin	●	● – ●●	●	●–●●	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	●●						●
Saponin	●●						●

*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

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
Tanin	●●-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
Tannin	Farm labour safety	Ammonia emission, Animal welfare

*Literature references*	Tannin
Bhatt et al., 2023	Comparing the efficacy of forage combinations with different hydrolysable and condensed tannin levels to improve production and lower methane emission in finisher lambs
Nayak et al., 2015	Management opportunities to mitigate greenhouse gas emissions from Chinese agriculture
Torres et al, 2023	Potential of nutritional strategies to reduce enteric methane emission in feedlot sheep: A meta-analysis and multivariate analysis
Lima et al., 2019	Dietary supplementation with tannin and soybean oil on intake, digestibility, feeding behavior, ruminal protozoa and methane emission in sheep
Wang et al., 2018	Supplementation of pelleted hazel (Corylus avellana) leaves decreases methane and urinary nitrogen emissions by sheep at unchanged forage intak

*Literature references*	Saponin
Torres et al, 2023	Potential of nutritional strategies to reduce enteric methane emission in feedlot sheep: A meta-analysis and multivariate analysis
Pepeta et al., 2024	Quantifying the Impact of Different Dietary Rumen Modulating Strategies on Enteric Methane Emission and Productivity in Ruminant Livestock: A Meta-Analysis
Mao et al., 2009	Effects of addition of tea saponins and soybean oil on methane production, fermentation and microbial population in the rumen of growing lambs
Congio et al., 2022	Prediction of enteric methane production and yield in sheep using a Latin America and Caribbean database
Arndt et al., 2021	Strategies to mitigate enteric methane emissions by ruminants – a way to approach the 2.0°C target.