Comparative analysis of greenhouse gas emissions from three beef cattle herds in a corporate farming enterprise
This study provided a gate-to-gate Life Cycle Assessment that modelled the greenhouse gas emissions (GHG) of three herds bred and grown by an integrated beef cattle enterprise across northern Australia. It involved modelling the GHG emissions of current herd management by the enterprise as a ‘baseline’ compared with ‘alternative scenarios’ of herd management. There were three herds (one herd of steers and two herds of heifers) each consisting of 5000 head of cattle. The baseline consisted of the steer herd grazing on growing then backgrounding properties and being finished at a feedlot. The two heifer herds grazed one respective backgrounding property each and were finished in a feedlot for their respective baselines. The alternative scenarios involved the steer herd bypassing the growing property and spending increased time at the backgrounding property. The heifer herds bypassed their respective backgrounding properties and they were grown and finished at a feedlot. The results show a 14% reduction of GHG emission intensities between the baseline and alternative scenario for steers and reductions of 29% and 4% between the baseline and alternative scenarios for the respective heifer herds. The variance in GHG emissions between the heifer herds can be explained by relative time spent grazing on the respective backgrounding properties and associated liveweight gain, versus time spent being grown and finished in the feedlot. In our modelling, herd GHG emission reductions occurred in the scenarios when time grazing on the growing or backgrounding properties (and associated liveweight gains) in the respective baselines exceeded 225–229 days for the heifer herds and between 206 days for the steers (depending on the relative liveweight gains on the properties). This means that if the cattle herds were to spend a longer time grazing on a property in their respective baselines than the number of days noted in our analysis, bypassing these properties would then result in net reductions in GHG emissions for the herds.