Genetic Variability of Methane Production and Concentration Measured in the Breath of Polish Holstein-Friesian Cattle.

The genetic architecture of methane (CH) production remains largely unknown. We aimed to estimate its heritability and to perform genome-wide association studies (GWAS) for the identification of candidate genes associated with two phenotypes: CH in parts per million/day (CH ppm/d) and CH in grams/day (CH g/d). We studied 483 Polish Holstein-Friesian cows kept on two commercial farms in Poland. Measurements of CH and carbon dioxide (CO) concentrations exhaled by cows during milking were obtained using gas analyzers installed in the automated milking system on the farms. Genomic analyses were performed using a single-step BLUP approach. The percentage of genetic variance explained by SNPs was calculated for each SNP separately and then for the windows of neighbouring SNPs. The heritability of CH ppm/d ranged from 0 to 0.14, with an average of 0.085. The heritability of CH g/d ranged from 0.13 to 0.26, with an average of 0.22. The GWAS detected potential candidate SNPs on BTA 14 which explained ~0.9% of genetic variance for CH ppm/d and ~1% of genetic variance for CH g/d. All identified SNPs were located in the TRPS1 gene. We showed that methane traits are partially controlled by genes; however, the detected SNPs explained only a small part of genetic variation-implying that both CH ppm/d and CH g/d are highly polygenic traits.