Researchers highlight new methods to predict methane emissions of dairy cattle

Methane emissions of dairy cows can be predicted with greater accuracy by milk fatty acids compared with milk infrared spectra. However, infrared milk spectra have a greater potential for practical high throughput application.

Methane is produced in the gastrointestinal tract of ruminants when feed is fermented. This methane is the largest source of greenhouse gases in dairy farming. The agricultural sector and the Dutch government have reached agreement on cutting greenhouse gas emissions by 30 percent by 2020, compared with 1990. The EU aims to reduce greenhouse gas emissions by 80 percent by 2050. However, the quantity of methane produced by dairy cattle is difficult to measure in practice. For this reason, researchers looked for an indicator for methane emissions that can be measured in the milk of dairy cattle.

Milk fatty acids and infrared spectra
Two techniques were investigated in the study, viz. milk fatty acids and infrared milk spectra. Milk fatty acids are unsuitable for large-scale routine analyses, whereas the infrared milk spectra are already used routinely by milk recording organizations to determine the fat, protein and lactose content of milk. To determine whether milk characteristics are related to methane emissions, the methane emissions from 218 lactating Holstein-Friesian dairy cows were measured in climate-controlled respiration chambers and milk samples were collected. The dairy cows received 30 different rations representative of dairy farming in the Netherlands, varying in roughage composition (e.g., fresh grass, grass silage, maize silage) and quality (e.g., harvest time and fertilization level).

The results indicate that methane emissions of dairy cattle can be measured significantly more accurate when using milk fatty acids compared with using infrared milk spectra. In this regard, it became clear that milk fatty acids evaluate the effect of forage type, level, and quality of methane emissions of dairy cattle better than milk infrared spectra.

However, infrared spectra are relatively easy and inexpensive to use in practice. Hence, repeated measurements from the same dairy cow are possible, which may result in a better prediction of the methane emissions. If this technique is developed further, milk infrared spectra may be a valuable indicator for methane emissions of dairy cattle.