Associations of rumen volatile fatty acids with phenotypic and genetic variation in methane production traits in angus cattle (#26)
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 (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). Many relationships of VFA concentrations with methane emissions apparent in 3hour measurements were reversed at 24 hours. Taking a rumen fluid sample during peak fermentation revealed stronger associations between methane emissions and VFA concentrations than previously reported 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 markers for methane emissions is still warranted.