Lauren Finlay's MSc Defence

Estimating feed efficiency and emissions of mature beef cows on pasture faces technical
challenges, with little information on the consistency of enteric emissions between the dry lot
and pasture. This research examined relationships between feed efficiency, enteric methane
(CH4), and carbon dioxide (CO2) of beef cows in the dry lot and pasture. The trial first monitored
feed intake, CH4 and CO2 production, weight, and backfat depth every 28 days for 10 weeks in
64 pregnant multiparous beef cows in the dry lot. Post-calving, cows were randomly assigned to
paddocks, twice measuring emissions and performance. Results demonstrated animals with low
RFI and RFI adjusted for backfat depth had lower intake per kg BW, methane and heat
production calculated from the respiratory quotient in the dry lot. Strong correlations were seen
between gas emissions in the dry lot and on pasture, demonstrating that dry lot emissions could
be predictive of emissions on pasture.