ABSTRACT: Disease resilience refers to productivity of an animal under disease. Given the high biosecurity of pig nucleus herds, traits that can be measured on healthy pigs and that are genetically correlated with disease resilience, i.e. genetic indicator traits, offer a strategy to select for disease resilience. Our objective was to evaluate mitogen stimulation assays on peripheral blood mononuclear cells from young healthy pigs as genetic indicators for disease resilience. Data were from a natural disease challenge in which batches of 60 or 75 naïve Yorkshire x Landrace piglets were introduced every three weeks into a continuous flow barn that was seeded with multiple diseases. In this environment, disease resilience traits, including growth, treatment, and mortality rates, were recorded on 3136 pigs that were genotyped with a high-density marker panel. Peripheral blood mononuclear cells from 882 of these pigs from 19 batches were isolated from whole blood collected prior to the disease challenge and stimulated with five mitogens: concanavalin A (ConA), phytohemagglutinin (PHA), pokeweed mitogen (PWM), lipopolysaccharide (LPS), and phorbol myristate acetate (PMA). Proliferation of cells was evaluated at 48, 72, and 96 hrs and compared to unstimulated samples (rest count). Heritabilities of cell proliferation were estimated using a model with batch as a fixed effect, covariates of entry age, rest count, and complete blood count proportions of lymphocytes, monocytes, eosinophils, and basophils, and pen, litter, and animal genetics as random effects. Heritability estimates were highest for response to ConA (0.30+0.09, 0.28+0.10, 0.17+0.10, and 0.25+0.10 at 48, 72, and 96 hrs after stimulation and for area under the curve across the three time points, respectively). Estimates were in a similar range for response to PHA and PMA, but low for PWM and LPS. Responses to ConA, PHA, and PMA were moderately genetically correlated with several disease resilience traits and in the expected direction but individual estimates were not significantly different from zero due to large standard errors. In conclusion, although validation is needed, mitogen stimulation assays, in particular based on ConA, show promise as genetic indicator traits for disease resilience.
