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Genomic selection for methane emission
Climate change is a growing area of international concern and it is well established that the release of greenhouse gases (GHG) is a contributing factor. Of the various GHG produced by ruminants, enteric methane (CH4) is the most important contributor. One mitigation strategy is to reduce methane emission through genetic selection. Our first attempt used beef cattle and a GWAS to identify genes associated with several CH4 traits in Angus beef cattle. The Angus population consisted of 1,020 animals with phenotypes on methane production (MeP), dry matter intake (DMI), and weight (WT). Additionally, two new methane traits: residual genetic methane (RGM) and residual phenotypic methane (RPM) were calculated by adjusting CH4 for DMI and WT. Animals were genotyped using the 800k Illumina Bovine HD Array. Estimated heritabilities were 0.30, 0.19 and 0.15 for MeP, RGM and RPM respectively, and estimated genetic correlations of MeP with DMI and WT were 0.83 and 0.80 respectively. Strong associations with MeP were found on chromosomes 4, 12, 14, 19 and 30. We have recently tried another approach in dairy cattle, where we aimed to enlarge the reference population for genomic selection by combining data on methane emissions in dairy cattle using data from 5 countries (Australia, Denmark, Ireland, the Netherlands and UK). The total dataset consists of 3,060 dairy cows, of which most were genotyped, but with various kinds of SNP chips. We ended up with a uniform set of SNPs for each cow. Even though three different types of measurement equipment (laser, sniffer and SF6) and protocols (measuring for 3 days, 1 week, multiple weeks) were used, these data will be analysed jointly to establish genetic and genomic parameters for enteric methane. The average methane production was 448 g/d in Australia (354 cows); 554 g/d in Denmark (1769 cows); 381 g/d in IRL (260 cows); 549 g/d in NL (457 cows); and 325 g/d in UK (216 cows). This clearly shows that the populations and diets are different in addition to the equipment and protocol. Therefore, a multi-trait approach will be used in the analysis. Following the experiences of a similar project (gDMI), it is expected that each country will benefit for contributing to an international reference set with increased accuracies of the estimates.
Keywords: Enteric methane, Genomic Selection, International collaboration