A modelling framework to evaluate benefits of animal adaptive capacity for livestock farming systems
Résumé
Livestock farming systems (LFS) are facing the challenge of producing more with less resource in a context of increasing uncertainty. Individual variability in the adaptive capacity of animals can be seen as a potential lever by which to improve LFS resilience. However, evaluation methods of such lever are currently lacking. The objective of this study was to develop a modelling framework to evaluate the effects of management strategy and environmental perturbation on the biological responses of animals within a herd. The framework is centred on the animal level, seen as: (1) an integrative level for biological functions, within which trade- offs in energy allocation are expressed; and (2) an elementary component of a population level, within which emergent properties such as resilience are expressed. At the animal level, adaptation is formalised through a dynamic pattern of energy allocation among life functions, allowing the characterization of adaptation in a multidimensional perspective. This representation allows a fuller description of adaptive capacities by representing different forms of adaptation. At the population level, adaptation is formalised as a trait evolving over several generation cycles, under the artificial selection achieved by the farmer through culling and breeding decisions. The originality of the animal model is to integrate life functions usually considered in animal nutrition models (growth, maintenance, lactation, gestation and reserves) with other traits like immunity, thermoregulation or behaviour. We finally apply the modelling framework to contrasted case studies of adaptation, for various environmental perturbations (thermal stress, pathogen pressure, resource shortage) and species.