Heritability of methane emission in Swedish Red cattle in northern Sweden

Abstract: Dairy cattle contribute a significant proportion of greenhouse gases (GHG), mainly methane (CH4), among other livestock species. Methane has a negative impact on climate; therefore, its reduction is a top priority for a sustainable dairy production system. Genetic selection could be a viable, permanent strategy to reduce methane production in dairy cows. This study aimed to estimate the heritability of CH4 emission in Swedish Red cattle. Genetic correlations of CH4 with production traits were also determined as a second objective of the study. A total of 1089 CH4 records were used in this study, collected from 194 Swedish Red cows from a single herd. The GreenFeed system was used to measure CH4 emissions. This study examined two specific CH4 traits: daily CH4 production (g/d) and CH4 intensity [g CH4/kg energy-corrected milk (ECM)]. The following traits were also analysed in this study: dry matter intake (DMI), ECM, milk yield (MY), and body weight (BW). Heritability estimates and correlations were calculated using univariate and bivariate animal models. The variance components for the calculation of heritability and genetic correlations were obtained using an AI-REML algorithm in the DMU software. The heritability (standard error in brackets) for CH4 production ranged from 0.24 (0.31) in the first parity to 0.44 (0.20) in the second and later parities. The estimates of heritability for CH4 intensity were 0.26 (0.35) in the first parity and 0.38 (0.20) in second and later parities. The heritability for ECM, MY, DMI and BW in the first parity were 0.40 (0.28), 0.58 (0.30), 0.80 (0.37), and 0.34 (0.39), respectively. The heritability estimates for ECM and MY were extremely low in the second and later parities: 0.01 (0.12) and 0.05 (0.14), respectively. Genetic correlation of CH4 with DMI, ECM and MY in the first parity were 0.48 (0.64), 0.23 (0.4), -0.06 (0.41) and 0.92 (0.77), 0.75 (0.64), 0.48 (0.41) in second and later parities respectively. The standard error of estimates was very high for genetic correlations. However, strong positive genetic correlation obtained between CH4 production and DMI in this study shows that precautions must be taken when selecting for reduced CH4 production as this may consequently reduce the dry matter intake of animals. The high standard error of estimates signifies the importance of enlarging the data set. The results of this study show that methane is a moderately heritable trait. Hence, it is possible to reduce CH4 emissions in Swedish Red cows through genetic selection.