The Environmental Impact and the Role of Animal Welfare for the Sustainability of Sheep Farming

The present doctoral thesis focuses on exploring the complexity of the sustainability of the sheep supply chain from various perspectives. Chapter 1 provides an overview on the environmental sustainability of livestock production, with a specific focus on sheep farming. Chapter 2 investigates the direct measurement of enteric methane (CH4) emissions from sheep across 14 farms using a Laser Methane Detector (LMD). It contrasts these measurements with estimates from predictive equations integrated into the CAP’2ER® tool. Although the CAP’2ER® estimates were higher by 1.5 kg CH4/head/year for dairy and lower by 0.9 kg CH4/head/year for meat farms compared to LMD measurements, both methods demonstrated a relatively strong correlation (ρ= 0.77; p < 0.001). Notably, the Root Mean Square Error of the estimates, using LMD as a reference, was 3.5, suggesting high predictive accuracy for methane production. The study demonstrates the feasibility of using LMD for non-invasive and large-scale CH4 emission assessments and the effectiveness of both approaches in ranking high and low emitters. Chapter 3 evaluates four Life Cycle Assessment (LCA)-based tools (CAP’2ER®, ArdiCarbon, SheepLCA, and CarbonSheep) for estimating the carbon footprint of the entire sheep supply chain across 24 European case study farms (12 dairy and 12 meat). The findings indicate substantial differences in carbon footprint estimates among the tools (p<0.001), with CAP’2ER® consistently providing higher figures due to its methodology for estimating CH4 emissions and its choice of emission factors. This thesis proposes guidelines to standardize estimates across these tools. Chapter 4 presents a review of the current understanding of animal welfare's role in the sustainability of livestock farming. Chapter 5 details scenario modelling studies conducted on dairy and meat sheep farming systems to evaluate the environmental costs of compromised welfare conditions using the Agrecalc© tool. Overstocking in dairy farms resulted in the most significant carbon footprint increase (+11%), while lameness in meat farms had a substantial impact (+8- 15%). These findings underscore the potential environmental benefits of improved animal welfare and the importance of targeting win-win mitigation strategies. Chapter 6 systematically summarizes the methodologies utilized to date for incorporating animal welfare indicators into LCA. Guidelines to facilitate this integration were proposed, and a case study of their application on a dairy sheep farm was presented. Chapter 7, introduces the need to adopt a holistic vision for sustainability assessments, including not only animal welfare and environmental sustainability, but also socio- economic factors. A common holistic framework was presented, developed through a multi-stakeholder consultation. The present doctoral thesis lays the foundation for future research and contributes to enhancing the knowledge for the sustainable transformation of the sheep sector, with a particular focus on the links between animal welfare and environmental sustainability.