201 Genetic parameters of disease in growing pigs under a polymicrobial natural disease challenge.

Abstract This study aimed to estimate genetic parameters of disease-related traits of growing pigs exposed to a natural polymicrobial disease challenge. The challenge was established by introducing seeder pigs into a wean to finish research facility and maintained by introducing a new batch of 60 or 75, ~40 day old clinically healthy Yorkshire x Landrace barrows into the challenge nursery (cNur) every 3 weeks, with a 1-week overlap with the previous batch, before the latter was moved to the finisher (FIN). Data used included individual health treatment(s) and mortality records on 4095 barrows from 7 breeding companies. Traits analyzed included treatment rates (TRR) and mortalities (MOR), categorized as meningitis (ME), respiratory distress (RD), scours (SC), unthrifty (UNTH), and other infections (OT). Analyses were by generalized and linear mixed models with genomic relationships. Heritability estimates for TRR and MOR were generally higher in cNur than in FIN. Compared to other disease categories, RD tended to have higher heritability estimates both in cNur (TRR-RD: 0.14±0.03, MOR-RD: 0.09±0.08) and FIN (TRR-RD: 0.07±0.03, MOR-RD: 0.18±0.09). Litter effects were generally low both in cNur and Fin but stronger in cNur (TRR-RD: 0.04±0.02, MOR-UNTH: 0.05±0.02). For RD, genetic correlation estimates among TRR and MOR in cNur and FIN were generally positive ranging from 0.40±0.18 for cNur TRR with FIN MOR to 0.95±0.30 for cNur MOR with FIN MOR. Corresponding genetic correlation estimates for other disease categories were either moderately negative (-0.19±0.32 for OT TRR between cNur and FIN), not positive definite, or the model did not converge. This study considered both TRR and MOR for different disease categories and growth phases for a large number of pigs under a severe natural polymicrobial disease challenge and provides valuable information to breed for disease resilience. Funding from Genome Canada, Genome Alberta, Genome Prairie, PigGen Canada, USDA NIFA (2017-67007-26144) and the National Pork Board Survivability Project.