Associations of Rumen Volatile Fatty Acids with Phenotypic and Genetic Variation in Methane Production Traits in Angus Cattle

Methane emissions from beef cattle contribute to greenhouse gas emissions in the atmosphere and waste gross feed energy consumed by cattle. Screening tests for methane emissions in cattle would be useful in genetic selection programs to reduce emissions. This paper reports results for 136 yearling-age Angus heifers and bulls tested for methane production in respiration chambers, and rumen fluid samples taken 3 hours post-feeding analysed for concentrations of volatile fatty acids (VFAs). A subsample of animals had repeat rumen samples taken 24 hours after feeding. The animals were fed a roughage ration offered at 1.2-times maintenance through testing. Concentrations of major VFAs (acetate, propionate and butyrate) and their proportions in the 3 hours post-feeding sample were strongly associated with methane production (g/d) (correlation coefficients up to 0.62), but less strongly with methane yield and residual methane production (correlation coefficients up to 0.17 and 0.28, respectively). Taking a rumen fluid sample during peak fermentation revealed stronger associations between methane emissions and VFA concentrations than previously reported for samples collected 24 hours after feeding. These relationships open the possibility of using VFA concentrations in rumen samples obtained at peak fermentation as indicator traits for methane emissions. For genetic selection, scrutiny of VFA as a screening test for methane emissions is still warranted.