Analyzing the factors driving the adaptability and robustness of mixed ruminant herds in grassland systems

Diversified systems that work to agroecology principles are a pathway worth exploring. However, the complexity of these systems and their high dependency on environmental conditions creates issues around the methods needed to assess them and the proxies needed to design them. The aim of this article is to characterize the robustness and adaptability of mixed herds in the face of environmental hazards. It also aims to identify the structural drivers (herd size and composition) of these two properties. Here we used the viability theory modelling approach calibrated on data from a long-term experiment to investigate the adaptability and robustness of mixed ruminant herds to meteorological and economic hazards, and their structural drivers. We applied our model to grass-based dairy-cattle and suckler-sheep herds. Results show that expected economic constraint is a determinant factor in the shape and composition of viable herds. Herd size and proportion of adult cattle in the herd are drivers of robustness in situations of uncertainty. The results also show that mixed herds are particularly valuable in situations with low economic requirements, especially in terms of herd adaptability to environmental hazards. Our results are consistent with existing mixed systems in western Europe but call for a change in the scale of analysis to include farm-level dynamics, associated management practices (land-use trade-offs, forage management, etc.) and uncertainties. This work questions the specialization of livestock farms and public policies to support agroecological transition and emergency aid for farmers. • Global change raises questions about the ability of grazing livestock systems to cope with uncertainties. • Using theory viability, we have modelled the robustness and adaptability of mixed dairy-cattle and suckler-sheep herds. • The economic constraint is the main factor driving the ability of mixed systems to cope with hazards. • The size and composition of herds may have synergistic or antagonistic effects depending on the economic constraints.