Year: 2025
Type: article
Abstract: One of the most promising strategies to permanently reduce methane emissions in dairy cattle is through genomic selection, where the primary goal is to identify and selectively breed low-emitting ruminants. An important step is to define which trait definition to use. Several methane phenotypes have been proposed in recent years. When measuring methane using breath analyzers (sniffers), 2 commonly used phenotypes are methane concentration (CH 4 c; ppm) and methane production (CH 4 p; g/d). However, for both phenotypes different definitions exist. For example, CH 4 c, the average per visit is commonly used, but other phenotypes involving the identification of "eructation" peaks have been suggested. For CH 4 p several formulas are available to calculate it, using CH 4 c or the ratio between CH 4 c and CO 2 concentrations as input, together with other production traits. Additionally, methane intensity, another phenotype of interest, is the amount of methane produced per milk unit (kg). Therefore, the aims of this study were to: 1) Estimate genetic parameters for 11 distinct phenotypes, including 3 CH 4 c definitions, carbon dioxide concentration per visit (CO 2 c), the ratio between CH 4 c and CO 2 c, 5 phenotypes for CH 4 p based on different formulas (Madsen, Chagunda, 2 of Kjeldsen, and IPCC-Tier2 as benchmark), and methane intensity (MeI). 2) Estimate genetic correlations between these methane phenotypes and milk yield (MY) and body weight (BW). A total of 149,726 sniffer (CH 4 c and CO 2 c) records were available from 7,600 Dutch Holstein cows measured between 2019 and 2024 on 68 farms. Data were analyzed with an animal repeatability model with fixed effects, including herd-year-season, week of lactation and lactation number with age of cow at calving nested. Estimated heritability values ranged between 0.16 and 0.30 for CH 4 c phenotypes, with the number of eructation peaks having the highest heritability. For CH 4 p, heritabilities ranged between 0.03 to 0.27, with Tier2 having the highest value. Heritabilities for ratio and CO 2 c were 0.08 and 0.13, respectively. Genetic correlations between CH 4 c phenotypes were moderate to highly positive, ranging between 0.49 and 0.85. Likewise, highly positive genetic correlations (between 0.89 and 1) were estimated for CH 4 p phenotypes, except for Tier2, which presented correlations between 0.04 to 0.37 with the other CH 4 p phenotypes. Both mean CH 4 c (avg) and sum of max peaks for CH 4 c (speaks) had moderate to high positive correlations (0.36–0.95) with the majority of the CH 4 p phenotypes (except Tier2). Methane intensity had moderate to high positive genetic correlations (0.38 to 0.80) with the majority of the phenotypes except for Kjeldsen2 (0.03) and Tier2 (−0.90). Milk yield had positive genetic correlations with all the methane phenotypes (0.04 to 0.94) except for MeI (−0.66) and Kjeldsen2 (−0.69). Body weight had close to zero genetic correlations with CH 4 c phenotypes (−0.09 to 0.07), and moderate positive to moderate negative correlation (−0.72 to 0.57) for CH 4 p phenotypes. Given their strong correlations with the other methane phenotypes, close to zero correlation with body weight, and no induced dependencies with BW and MY, as seen with the CH 4 p phenotypes, avg and speaks appear to suitable proxies for methane emissions when using sniffers.
Source: JDS Communications
Institutions: Wageningen University & Research, CRV (Netherlands)
Language: English
Subfield: Genetics
Domain: Life Sciences
SDGs: Zero hunger, Climate action
Open Access status: gold
Estimated APC paid: $1,310
OpenAlex ID: W4415016802