Methane production and what can we do about it?

Depending on body size and nutrition, dairy cows can produce up to 500 litres of methane (CH₄)/day, contributing between 45-50% of a dairy farm’s carbon footprint (CFP). Methane mainly comes from enteric fermentation, the natural process of fibre digestion in the rumen. Measures to reduce total CH₄ emissions, as well as per kg of milk, include:

1. Forage quality – the higher the better. Higher D value (digestibility) forages have a lower fibre content, meaning less CH₄ production during rumen fermentation. They also enable higher intakes, leading to more milk output and so less CH₄ per kg of milk. Cutting date will have the biggest influence on forage quality.

2. Increase concentrates – feeding more concentrates in place of silage will reduce CH₄ production. Concentrate type is also important as those with a higher NDF (fibre) content e.g., sugar beet pulp and soya hulls, will produce more CH₄ than starchy, lower NDF cereals and some protein sources. A milk yield response is also likely, again reducing CH₄/kg of milk.

3. Age at first calving – this can have a significant impact on total herd emissions as dairy heifers will be producing CH₄ but have no milk output to spread emissions over. Research by AFBI showed that reducing calving age of heifers from 27 to 24 months reduced the CPF by 7% for a typical moderate input herd in Northern Ireland.

4. Replacement rate – reducing the replacement rate means less heifers are required to maintain herd size. Longevity also improves as a typical 33% replacement rate means a cow lasts for three lactations, but this increases to five lactations with a 20% replacement rate. Focus on health and fertility to reduce replacement rate and heifer requirements.

Not only will these improvements reduce a farm’s CFP, but they should also bring financial benefits.

For more advice, visit the dairy section of our website or, if you’ve got a specific query, call or email our advice line, details here.