Essential oils are plant extracts that can enhance the palatability of dairy rations. These additives typically include compounds such as coriander seed oil, eugenol (from cloves), geranyl acetate and geraniol. By improving the sensory aspects of rations using these additives, feed intake, nutrient use efficiency and consequently cattle performance, can be improved.
In the UK essential oils are currently only authorised to be used to improve the sensory qualities of rations. Any use or claim relating to methane reduction would require a separate authorisation following formal assessment.
Research suggests that essential oils can also influence rumen function, leading to lower methane emissions. This evidence indicates that essential oils could shift the microbial population in the rumen; therefore, influencing fermentation patterns linked to methane production. Some studies have observed reductions in methane output of 5–10 %, although results can vary depending on diet, system and inclusion rate. These findings are currently limited to research settings and are not an authorised basis for use in methane reduction.
Alongside potential emissions benefits, there is some evidence of performance gains from essential oil supplementation. For example, milk yield increases of around 4% have been reported in some research. But, as with any feed ingredient, outcomes will depend on how it fits within the wider dairy ration and herd management.
In line with their current authorisation as sensory additives, essential oils can be included in feed in a number of ways. Liam Sinclair, Professor of Animal Science at Harper Adams University, said:
For farms involved in the UK Dairy Carbon Network, essential oils may be considered as part of the wider evidence base on feed-based approaches, including potential effects on feed efficiency. However, they are not currently an approved methane mitigation tool and should only be used in line with their authorised function. Adding an ingredient such as essential oils will depend on a number of factors. The right choice will depend on their farm system, feeding approach and business priorities.
Our Farm Liaison Officers and technical support teams are supporting participating farms by discussing the available options and sharing the latest evidence to help them decide what could work best in their specific systems.