Sustainable dairy breeding: reducing methane emissions in the Netherlands and Flanders

Abstract

Dairy cows contribute to the emission of methane (CH4), a strong greenhouse gas, into the atmosphere. Reducing CH4 emissions from dairy cows will lower the impact of livestock on global warming. Breeding could be an effective reduction method, and estimating breeding values was the objective of this work. The CH4 emission of 11,595 dairy cows in 89 Dutch herds was measured with sniffers in parts per million (ppm) of exhaled air. The CH4 emission of 397 dairy cows from 1 Dutch herd was measured in grams per day (g/d) of exhaled air using GreenFeed. CH4 measurements took place from 2019 to 2025 (sniffer) and from 2022 to 2025 (GreenFeed). All observations during a week on a cow were averaged into week observations. There were 226,449 week observations for ppm and 11,824 week observations for g/d. Genetic parameters were estimated with ASReml 4.2 using an animal multi-trait repeatability model. Heritabilities (h2) were 0.14, 0.14 and 0.19 for ppm and 0.34, 0.37 and 0.37 for g/d, for respectively parity 1, parity 2 and parity 3 and later (3+). Genetic correlations between different parities for ppm were 0.74, 0.47 and 0.79, and for g/d 0.73, 0.38 and 0.69, between respectively 1 and 2, 1 and 3+, and 2 and 3+. An overall breeding value was calculated for g/d based on traits in parity 1, 2 and 3+. By using a selection index, extra information was added to the overall breeding value in g/d. Traits in the selection index were kg milk production, kg fat production, feed intake and body weight with genetic correlations of respectively 0.39, 0.19, 0.20 and 0.09. The average CH4 emission of a dairy cow was 435 gram per day with a genetic standard deviation of 36 grams per day. The heritability of the trait, the size of the genetic standard deviation, and the fact that genetic correlations with health traits were estimated to be small, makes breeding an effective and powerful tool to mitigate CH4 emissions from dairy cattle in the Netherlands and Flanders. The overall breeding value for CH4 in grams per day is published in the Netherlands and Flanders from April 2025 onwards.