Genetics of the relationships between immunocompetence, resilience, and production in chickens

It is hypothesized that selection for production traits in animals has resulted in allocation of resources to production at the expense of other physiological processes, such as immune function: This resource allocation led to trade-offs between production and other life functions. The aim of this study is to dissect the genetic basis of resource allocation between immunocompetence, resilience, and production. Immunocompetence is dened as the level of natural antibodies (NAb). Breeding for higher NAb levels was previously shown to increase avian pathogenic Escherichia coli resistance in chickens, and was hypothesized to improve humoral adaptive immunity. Resilience is the capacity of an animal to be minimally affected by disturbances or to rapidly return to the state pertained before exposure to a disturbance. We hypothesize that less resilient animals are more susceptible to environmental perturbations and will consequently show more uctuations in day-to-day production than more resilient animals. A daily-measured and relevant production trait in chickens is egg production, which was therefore selected for further investigation for both production and resilience. The study population consists of one genetic line with three subpopulations: (1) a population of approximately 3,000 purebred chickens with observations for NAb (i.e. immunocompetence); (2) a population of approximately 18,500 purebred chickens with daily observations for egg production (i.e. resilience and production); and (3) a population of approximately 1,200 crossbred sire-families with daily observations for egg production (i.e. resilience and production). By estimating heritabilities and genetic correlations with double hierarchical generalized linear models, we will investigate and quantify relationships between immunocompetence, resilience, and production. This leads to better understanding of resource allocation, and gives opportunities for livestock breeding organizations to breed for livestock with good immunocompetence, resilience, and production.