Reducing enteric methane emissions of dairy cows

Methane emissions associated with milk production can be reduced via changes to herd management, genetics, feed and additives.

A recent Climate Farm Demo webinar hosted by Benoit Rouillé from the French Livestock Institute explored the approaches available to reduce methane emissions from dairy cows, as well as available options to measure and predict methane emissions from dairy cows.

Enteric fermentation is responsible for approximately half of the greenhouse gas (GHG) emissions associated with dairy milk production, making it an important source of emissions to address. Thankfully, there are several options available to reduce methane emissions from dairy herds. 

Herd management changes aim to improve efficiency, as producing the same quantity of milk with less animals will reduce the amount of methane emitted per litre of milk produced. Improvements to genetics focuses on selecting animals that produce less methane, while feed supplementation and use of additives influence the processes going on in the rumen itself.  

Herd management  

This can be achieved by reducing age at first calving, reducing replacement rate, improvements to herd health, improvements to feed efficiency and improvements to productivity. Depending on situation, these will all enable a low to medium reduction of methane in the herd. 

This approach is applicable for all farms and will improve productivity and reduce methane and other GHG emissions from the herd, but there could also be an increase in GHG emissions from feed and fertilisers, so there is a need to find a balance between the approaches.

Genetics

Speaking in the webinar, Benoit highlighted that there is research showing that selection of low emitting animals is possible. This approach is low cost and efficient in the long term, making it part of the solution, but not necessarily consistent across the diversity of feeding systems used in dairy.

Feed components and supplementation

Methane production in the rumen is a multi-step process, which means there are multiple approaches available to disrupt the process and reduce the overall quantity of methane produced. 

The food that arrives in the rumen is used by microbes which break it down and produce volatile fatty acids (VFA) and H₂, Feed supplementation can help reduce the activity of these first microbes in the process, which in turn reduces the amount of methane produced.

Diet supplementation using lipids, cashew nut liquid or nitrates can result in a low to medium reduction of methane production. Forages can also be part of the solution, by adjusting the digestibility of different forages to skip or switch the normal pathways of methane production. It is also possible to reduce the pH of the rumen to disrupt this process, however this approach can be tricky due to the need to avoid causing acidosis.

Mixing supplements into the diet is easier in indoor feeding systems, but tannins such as chicory and sainfoin can be used in grazing systems. Tannins also work by reducing the activity levels of the microbes in the rumen, so less H₂ is produced and therefore less available to produce methane in the later steps of methane production.   

Feeding components and supplementation will improve farm efficiency, particularly in terms of nitrogen use. In grazing systems they can improve carbon sequestration, and could also reduce fertiliser use. However, there can be a cost associated with adding a supplement to the diet.

Additives

After the first microbes have produced H₂ and VFAs, it is the methane producing microbes – known as methanogens – which produce the methane itself. These methanogens produce enzymes which facilitate the production of methane, and feed additives work by acting on these enzymes to reduce methane production.

Bovaer and algaes are the most-known feed additives for reducing methane emissions from dairy cows. Bovaer can offer approximately 30% reduction in methane emissions,  and algaes could offer more than 40%.

Feed additives need to be mixed into the diet, so are only an option for indoor herds currently.  They are efficient, there is no residue in the milk produced and no impact on health, however some might be toxic if used in too high quantities. There is also a question about acceptability to farmers and consumers.

However, it is important to consider whether there is sufficient volume of additives to feed a high number of cows. In the case of algaes, these are mainly tropical species, so less available in Europe.

Combining methane reduction strategies

Speaking in the webinar, Benoit shared that overall, there is potential to reduce methane emissions by 50%. This can be broken down as follows:

• Herd management offers 5-10% reduction
• Genetics offers 10% reduction over period of 10 years
• Changes to feed components and supplementation offers 10-15% reduction
• Additives can offer approximately 30% reduction

Because methane emissions represent half of the GHG emissions from milk, reducing methane emissions by 50% results in a 25% reduction in milk carbon footprint.    

Watch the webinar to find out more about the approaches to reduce methane emissions from dairy production and how these emissions can be measured and predicted.