Optimising beef systems: economic and environmental trade-offs
Item statusRestricted Access
Embargo end date07/03/2023
Marques, João Gabriel Oliveira
Current environmental rhetoric has highlighted the importance of seeking livestock production systems that reconcile competing objectives, especially environmental impacts. Profit margins in cattle systems are small and feeding the animals accounts for most of the costs. Hence, diet optimisation is an important aspect of beef systems. A promising sustainability strategy in Brazil is the integration of beef cattle with biofuel production, reducing environmental impact footprint, restoring pasture, and using agro-industrial by-products of ethanol in animal diet. These strategies can help reduce land-use change, minimising biodiversity loss and greenhouse gas emissions (GHGs). This is an important challenge in Brazil and helps in achieving its commitments presented at COP21 to reduce GHGs by 37% (vs 2005 baseline). Minimising environmental impact (EI) in these systems is a complex problem that can be solved through optimisation models, e.g., linear programming, nonlinear programming, heuristics. However, reducing EI may incur trade-offs in operational profit. Such models can also be used for sensitivity analysis, i.e. to assess the impact on the solution from changes in variables and input parameters, e.g., by-products costs, beef demand. This PhD thesis aims to fill gaps in cattle diet optimisation. Chapter 1 introduces and contextualises the scope of this thesis. Chapter 2 addresses the nonlinear animal growth problem, showing that the (usually avoided) nonlinearity can be efficiently solved using modern techniques. Chapter 3 presents a methodology to obtain the competitive cost of agro-industrial by-products to be included in animal diet considering market competition with other feedstuff. Chapter 4 builds on state-of-the-art research to minimise environmental impacts through diet optimisation. The novelties of this model are (i) working with maximum profit diet formulation rather than least-cost diet, and (ii) adding predicted enteric fermentation and manure emissions to be considered in the formulation along with the feedstuff life cycle assessment (LCA). Finally, Chapter 5 concludes the work by commenting on the issues addressed and the remaining challenges on the topic.