Heritability Estimates of Methane Emissions in Sheep

In order to select animals for reduced methane emissions, a rapid and low cost measurement method is essential for industry use. The objective of this study was to determine the genetic parameters of methane emissions and their genetic correlations with key production traits. The trial measured the methane emissions, at 5 minute intervals, of 1255 sheep placed in respiration chambers for 2 days, with repeat measurements several weeks later for another 2 days. Methane outputs were calculated for CH₄ (g/day) and CH₄/kgDMI for each of the 4 days. Single trait models were used to obtain estimates of heritability and repeatability. Heritability of CH₄ was 0.29, and for CH₄/kgDMI 0.13.  Repeatability between measurements 14 days apart were 0.55 and 0.26, respectively.  The genetic and phenotypic correlations of methane outputs with various production traits (liveweight, fleeceweight, muscle depth) measured in the first year of life, were estimated using bivariate models.  These correlations were low and not significantly different from zero after correction for number of tests for the CH₄/kgDMI trait. These results indicate that there is genetic variation between animals for methane emission traits even after adjustment for feed intake and that the traits studied are repeatable. Current work includes the creation of selection lines from these animals, and investigations into shorter and alternative measurement and breeding value estimation techniques including genomic selection.