Early 2018 was an exciting time for the “natural disease model” established as part of our current Genome Canada project on pig disease resilience and sustainability. This is a very ambitious project that challenges naïve pigs with a cocktail of economically important swine pathogens. The project is two thirds of the way through, with samples and data collected on more than 2,000 pigs. We now have a critical mass of data, and some of the first analyses are beginning to show very interesting results, which we have just presented at PAG, the 2018 Banff Pork Seminar and the 2017 North American PRRS Symposium and NSIF Joint Conference (see YouTube video here).
Gentec CEO Graham Plastow presented the model and some of the latest results at PAGXXVI. The model was dreamt up by a team of researchers working closely with PigGen Canada, which represents the majority of pig breeding companies in Canada. Previous work shows that pigs could be selected for reduced susceptibility to the major diseases porcine reproductive and respiratory syndrome (PRRS) and porcine circovirus associated disease (PCVAD) but these diseases are multifactorial and involve numerous other pathogens so a single disease challenge may not provide the desired answer. Industry was asking: Would selecting for reduced susceptibility to these diseases pay off or should we also include the less destructive but endemic diseases at the commercial level that impact production?
One of the PRRS virus challenges at Kansas State University in our former Genome Canada-funded project intrigued the team and especially Plastow. Even though all the pigs in these challenges were infected and became sick, some recovered quickly and grew as well as the uninfected controls. This phenotype would undoubtedly be attractive to producers, especially if it occurred no matter what the underlying cause. Some challenge studies also suggested that the immune system was different in these pigs, even before challenge. What if these differences could be determined in healthy pigs at the top of the breeding pyramid? If these pigs and their progeny were more resilient to different diseases, it could revolutionize the selection of healthier pigs, potentially improving profits for producers, increasing animal welfare and reducing the use of antibiotics.
Austin Putz, a PhD student with Jack Dekkers at Iowa State University, has shown that new resilience traits being generated in the model are moderately heritable. A graduate student, Laura Tibbs, also working with Dekkers, is using data generated by John Harding’s team at USaskatchewan to show that natural antibodies may explain some of this variation. Other teams at UGuelph and UAlberta are working on their favourite assays and again generating predictors of resilience. The next stage is to validate these results and generate tools that can enable breeders to select for this valuable trait.
There is still a long way to go, but some of these first descriptions of resilience are very encouraging.