Heritability of methane production and genetic correlations with milk yield and body weight in Holstein-Friesian dairy cows.

Greenhouse gases (GHG), including methane (CH4), play an important role in global warming. Methane has 28 times the global warming potential of CO2. Although in SA the figures are much lower due to the small size of the dairy industry, the global dairy supply chain produces 20% of the livestock-sector’s GHG, and 46.5% of that is from enteric CH4.

Therefore, reducing CH4 production from dairy cattle will have an important influence on the total global livestock CH4 emissions. One possible strategy is to use genetic selection to reduce CH4 production. However, before genetic selection for CH4 production can be introduced, genetic parameters of CH4 production and correlations with production traits are required. Currently, few estimates of heritability and correlations with related traits are available. Therefore, the objectives of the study by Dr I. S. Breider and colleagues were (1) to estimate the heritability of CH4 production (g per day), measured over a consecutive period of 5 months, and (2) to calculate correlations between CH4 production (g per day) and milk yield (L per day) and body weight (kg). Their results were published in the Journal of Dairy Science, Volume 102 of 2019, page 7277 to 7281. The title of the paper is: Heritability of methane production and genetic correlations with milk yield and body weight in Holstein-Friesian dairy cows. 

Data were available from 184 Holstein-Friesian cows. Methane production was measured in the milking robot during milking. In total, 2456 observations of CH4 production were available. Milk yield and body weight were obtained at every milking. In total 4567 observations for milk yield and 4570 observations for body weight were available. Restricted maximum likelihood, using random regression models, was used to analyse the data. 

The heritability (standard error given in parentheses) for CH4 production ranged from 0.12 (0.16) to 0.45 (0.11), and the genetic correlations with milk yield ranged from 0.49 (0.12) to 0.54 (0.26).

The study confirmed that CH4 production is moderately heritable, and therefore it is possible to select cows for lower CH4 production. The positive correlation between CH4 production and milk yield, however, indicated that care must be taken that, when selecting for lower CH4 production, milk production is not reduced concurrently. To maximize reduction in CH4 production and limit associated effects in related traits, both CH4 production and milk yield should be included as part of a selection index in breeding goals.