Genetic control of greenhouse gas emissions

Abstract

Climate change is a growing international concern and it is well established that the release of greenhouse gases (GHG) is a contributing factor. The European Union has committed itself to reduce its GHG emissions by 20% by the year 2020 relative to 1990 levels. Of the various GHG produced by ruminants, enteric methane (CH4) is the most important contributor, with a global warming potential 25 times that of carbon dioxide (CO2). Recent studies have shown that natural variation among animals exists in enteric CH4 emission. This variation can be used to breed cows with low CH4 emission, with expected progress per generation in terms of CH4 reduction ranging from 10 to 20%. Successful animal breeding strategies require measurements on a large population of animals. With the recent successful incorporation of genomic information into breeding schemes the reliance on very large populations of phenotyped animals is relaxed. The rumen is the major site of methane production in which anaerobic archaeal microorganisms convert H2 and CO2 to CH4. Methane is a natural by-product of anaerobic respiration, produced predominantly in the rumen (~90%), and to a small extent in the large intestine (~10%). The major factors that determine methane production include the amount of feed consumed by the ruminant and the digestion of that feed. As more feed is ingested, more methane is produced, but the portion of methane per kg dry matter intake (DMI) decreases with increasing feed intake. International collaboration is essential to make progress in this area. This is both in terms of sharing ideas, experiences and phenotypes, but also in terms of coming to a consensus regarding what phenotype to collect and to select for.