Deliverable D3.4 A ‘Robustness’ simulation model to predict short and long-term animal responses to fluctuations in nutrient supply and in environmental conditions

Improving robustness for farm animals is seen as a new target of breeding strategies. However, robustness is a complex trait and not measurable directly. The objective of this deliverable is to quantify and characterize (elements of) robustness in growing pigs. Robustness can be characterized by examining the animal’s response to environmental perturbations. Although the origin of environmental perturbations may not be known, its effect on the animal can be observed, for example through changes in voluntary feed intake. Perturbations such as heat stress and sanitary challenges typically have a negative and transitory effect on the voluntary feed intake. We developed a generic model and data analysis procedure to detect these perturbations, and subsequently characterize the feed intake response of growing pigs in terms of resistance and resilience as elements of robustness when faced with perturbations. We hypothesize that there is a target trajectory curve of cumulative feed intake, which is the amount of feed that a pig desires to eat when it is not facing any perturbations. Deviations from this target trajectory curve are considered as a perturbation, which can be characterized by its duration and magnitude. It is also hypothesized that, following a perturbation, animals strive to regain the target trajectory curve of cumulative feed intake. A model based on differential equations was developed to characterize the animal’s response to perturbations. In the model, a single perturbation can be characterized by four parameters. The start and end times of the perturbation are “imposed” by the perturbing factor (e.g., a period of heat stress) while two other parameters describe the resistance and resilience potential of the animal to the perturbing factor. One parameter describes the immediate reduction in daily feed intake at the start of the perturbation (i.e., a “resistance” trait) while another parameter describes the capacity of the animal to adapt to the perturbation through compensatory feed intake to re-join the target trajectory of cumulative feed intake (i.e., a “resilience” trait). The model has been employed successfully to identify the target trajectory of cumulative feed intake in growing pigs and to quantify the animal’s response to a perturbation by using feed intake as the response criterion. The model has been developed at INRA and benefitted from feedback from frequent WP3 meetings and annual project meetings (especially from Kaposvár University, Newcastle University, Topigs Norsvin, and IRTA).