A Natural Challenge Model for Disease Resilience in Wean-to-Finish Pigs

Selecting for tolerance or resistance to specific diseases may be detrimental for the ability of the animal to respond to other major pathogens. In commercial herds, disease often reflects the outcome of infection with multiple pathogens at different stages of development. Thus, the objective is to determine the genetic basis of resilience to multiple common diseases, which is defined as the ability to respond to infection to minimize the impact of disease. To investigate the genetic basis and develop early predictors of resilience, a natural challenge model has been established at the wean-to-finish research facilities at the Centre de Développement du Porc du Québec. In this project, batches of 60 to 76 F₁ (Yorkshire x Landrace) barrows from healthy multiplier herds representing 7 PigGen Canada (www.piggencanada.org) members are entered into a clean nursery for 3 weeks (at 17-29 d of age), where samples and phenotypes under healthy conditions are collected and then moved into a continuous flow grow-finish facility at ~60 d of age (52-72 d) that was seeded using pigs from commercial farms with targeted diseases to simulate a commercial health environment. Alternating medicated and non-medicated feed is used to moderate the disease challenge within set limits. These results include the first 441 of ~3,300 pigs that will be evaluated over 3 years. Each pig was weighed every three weeks and mortality and treatment records were recorded throughout. In the finisher, individual feed and water intake were recorded. In total, 35% of pigs died or were humanely euthanized. Basic mixed models were fit with litter as a random effect as an indicator of the heritability due to the lack of pedigree and genotypes currently. Models for average daily gain (ADG) in the nursery and in the finishing unit included fixed effects of batch, entry age (nursery only), days on test (finishing only), batch*pen, and mortality (1/0), and litter as a random effect. Litter explained 25.9% of the phenotypic variation for nursery ADG and 20.5% for finishing ADG. ADG in the nursery and finishing unit showed a phenotype correlation of 0.19. Future analyses will focus on developing early predictors of resilience and include dense SNP genotype data for genome-wide association studies and genomic prediction to dissect and utilize the genetic basis of disease resilience. Funding from Genome Alberta (ALGP2), Genome Canada, and PigGen Canada.