NON-TECHNICAL SUMMARY: Infectious disease and other external stressors are large cost components in pork production and are detrimental to animal welfare. Resilience is defined as the ability of an animal to perform and thrive despite exposure to stressors (infectious and/or non-infectious) and has been shown to have an important genetic component. However, selection for improved resilience is hampered by lack of phenotypes that can be collected on selection candidates in breeding populations, which must be kept in facilities with high biosecurity. In ongoing research we have developed methods to identify pigs that are more resilient to disease in biosecure environments, based on data from large numbers of pigs that were exposed to a multifactorial natural disease challenge, with extensive phenotypes collected, including body weights, daily feed and water intake, and mortality and morbidity, as well as immune assays and -omics data prior to entry into the challenge. This project capitalizes on the natural challenge data and samples that will be generated on a subset of 960 pigs by evaluating response to stress in a retrospective manner based on measurement of cortisol and DHEA concentrations in hair. As hair grows, the stress hormones cortisol and DHEA are deposited, reflective of their concentration in circulation. The concentration of cortisol and DHEA in hair, therefore, reflect the animal’s response to stressors that the animal was exposed to when the hair was grown, like rings on a tree The overall goal of this project to develop and refine indicators of resilience that can be collected on pigs in commercial farms and/or in nucleus herds in the form of hair samples. Specific objectives are to evaluate the genetic basis, as well as the phenotypic and genetic relationships of differences in retrospective measures of stress response in healthy nursery pigs and in disease-challenged grow-finish pigs with performance and disease resilience, and to evaluate phenotypic and genetic associations of the blood transcriptome of healthy nursery pigs with their retrospective measures of stress response both prior to and during the disease-challenge. Project deliverables will impact the industry through development of the use of hair non-invasive sample to measure indicators of resilience on young health pigs, as well as the scientific community by providing knowledge on the relationship between disease resilience and resilience to other external stressors.
OBJECTIVES: The main goal of this proposal is to evaluate use of measures of retrospective stress from hair collected on young healthy pigs, and on hair grown during a severe polymicrobial natural disease challenge, as phenotypic and genetic indicators of resilience to infectious and non-infectious stressors. In addition to developing and evaluating tools to measure general resilience, we will also be able to shed light on the relationship of disease resilience with resilience to non-infectious stressors, potentially allowing refinement of biomarkers or genomic predictions. This project leverages the collection of detailed individual data on health, growth, and daily feed and water intake on ~980 pigs that will be exposed to an already established multifactorial natural disease challenge, and the genotyping of all pigs for over half a million Single Nucleotide Polymorphism (SNPs) across the genome, based on funding from Genome Canada and industry collaborators. The specific objectives of the current proposal are:1 Evaluate the genetic basis and relationships of differences in retrospective measures of stress response from hair among healthy nursery pigs and among disease-challenged grow-finish pigs.2 Evaluate the phenotypic and genetic relationships of retrospective measures of stress response from hair in healthy nursery pigs and in disease-challenged grow-finish pigs with performance of nursery pigs and with disease resilience of grow-finish pigs.3 Evaluate the phenotypic and genetic associations of the blood transcriptome and of the complete blood count of nursery pigs with retrospective measures of stress response from hair of healthy nursery pigs and of disease-challenged grow-finish pigs.