A cow’s genes influence her methane emissions. This means that dairy farmers could permanently lower the emission by selective breeding for this characteristic. However, it is not easy to find the one cow that exhales the least methane among several hundred others, writes researcher Yvette de Haas of Wageningen Livestock Research in Journal of Dairy Science.
Cows convert grass into animal proteins, with the greenhouse gas methane as a by-product. A cow belches to get rid of this gas, thus releasing it into the atmosphere. There is a method to measure this emission precisely for individual animals. A respiration chamber, a chamber in which a cow stands for a full day, provides a very accurate image. However, this is much too expensive and labour-intensive for many dairy farmers.
An alternative can be found in a methane sniffer, a small sensor that registers methane. Farmers could place these in mangers to measure the methane concentration in the breath of a cow while she is eating. The problem is that these measurements are not representative for the remainder of the day. Despite this, De Haas thinks the measurements can be used. ‘A cow is a creature of habit, but rarely eats at the exact same time every day. If you measure over many days and average the values, it will yield a sufficiently accurate measurement.’
But that is not the full story, as agreements have yet to be made on the exact breeding criterium, says De Haas. This could be methane emission per litre milk produced, per kilogramme feed ingested, or per kilogramme of the cow’s weight. It is a global custom to choose a unit focused on production; in this case, per litre milk produced or per amount of total produced proteins (from both milk and meat). According to De Haas, the latter is the more obvious choice for dairy cattle, as cows produce both milk and meat.
De Haas expects that guidelines for methane emissions by cattle will be established within ten years. ‘I expect that to happen first in the countries where the agricultural sector is responsible for the bulk of methane emissions, like in New Zealand. This is not the case in the Netherlands, but it will certainly bring about some changes here.’ Food cooperatives and companies also play an important part. They increasingly often require ingredients that have been produced sustainably from their suppliers. If they start doing this for milk as well, breeding cooperations will have to be able to provide their members with cows that belch less methane.