View source for Section 20: Merging and sharing data in genetic evaluations

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<b>NOTE: This version of Section 20 has been approved by the working group's Chair.  Please be aware that further revisions may occur before final review and approval by the Board and ICAR members per the [[Approval of Page Process]].
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Early 2016 an attempt to make cross country evaluations of CH<sub>4</sub> emissions from Holstein dairy cattle was initiated. The work was based on data from NL, DK, AUS, UK and IR. In total, 12,820 weekly CH<sub>4</sub> emission records from 2,857 cows were available. Although different equipment was used across countries to measure CH<sub>4</sub> emissions, the research aimed to define similar CH<sub>4</sub> output phenotypes in each country. The analysed CH<sub>4</sub> traits, that are available in each country, are (1) CH<sub>4</sub> production in g/d, and (2) CH<sub>4</sub> intensity in g/d per kg fat protein corrected milk (FPCM). In addition to these CH<sub>4</sub> traits, CH<sub>4</sub> concentration (in ppm) was available in Denmark, the Netherlands and UK, and the ratio between CH<sub>4</sub> and CO<sub>2</sub> concentration was available in Denmark and the Netherlands.

Bivariate analyses were carried out to estimate genetic correlations between countries, using an animal linear mixed model for all traits. Both univariate and bivariate analyses were repeated with the GRM as well. With all weekly records, standardizing the trait in the full dataset increased the heritability for CH<sub>4</sub> production from 0.03 to 0.06. The heritability for CH<sub>4</sub> intensity was slightly higher. The highest heritability with the full dataset is estimated for the standardized CH<sub>4</sub> concentration (0.19). Correlations estimated among CH<sub>4</sub> traits estimated with either the pedigree or the GRM were in same direction and of similar magnitude. The genetic correlations show that when CH<sub>4</sub> production increased, the CH<sub>4</sub> concentration and the ratio between CH<sub>4</sub> and CO<sub>2</sub> increased as well.

The approach is novel, and no other attempt has been performed to make genetic analysis of CH<sub>4</sub> traits across countries. The analysis can be repeated in future studies where more data hopefully will be available, and more effort can be made into improving both the fixed and random part of the model.