Genetic Parameters for Methane Emissions Using Indirect Prediction of Methane and Its Association with Milk and Milk Composition Traits

SIMPLE SUMMARY: Methane is a major source of greenhouse gases, and ruminant animals are mainly responsible for its emission. Measuring methane in a large group of animals is expensive and requires specialised equipment. Therefore, direct animal selection aiming at reducing methane production by dairy cows on a large scale is difficult. This study aims to predict methane production based on milk yield production, estimate heritability for methane production, and the genetic correlation between methane production and milk production. The indirect approach using milk traits and genetic parameters shows that methane production is a heritable trait. High genetic correlations were estimated between methane production and milk traits. That indicates the selection to decrease methane production would also negatively affect milk yield and composition. ABSTRACT: The study covers milk yield and composition data for 17,468 Polish Holstein-Friesian cows. Methane production (g/lactation per cow, MP) for dairy cow were predicted using three methane production equations (MPE) that took into account: milk yield (MPE1), energy corrected milk (MPE2) and both milk protein concentration (%), and energy-corrected milk (MPE3). The average amounts of methane produced for each cow per lactation were 31,089 g, 46,487 g, and 51,768 g for MPE1, MPE2, and MPE3, respectively. Repeatability models were used to estimate genetic parameters for MP. The estimated heritabilities for MPE1, MPE2, and MPE3 were 0.30, 0.24, and 0.24, respectively, with a standard error of 0.01. High genetic correlations (>0.76) were obtained between methane and milk yield, protein, fat, lactose and dry matter contents in milk for MPE1, MPE2 and MPE3. Still, a moderate genetic correlation (0.34) was obtained between methane and fat content (MPE1); the standard error of the estimated genetic correlation was less than 0.05. The results of the current study indicate that genetic selection aimed to reduce MP in dairy cows is possible. However, such direct genetic selection could cause a negative genetic response in milk yield and composition due to negative genetic correlations between MP and milk yield and composition.