Integrating Disease Diagnostic Data with Pre-Weaning Performance and Post-Weaning Productivity to Identify Risk Factors Associated with Pig Mortality in a U.S. Swine Production System

Aggregated diagnostic data collected over time from a swine production system is an important data source to investigate swine productivity and health, especially when combined with other records concerning the pre-weaning and post-weaning phases of production. The combination of multiple data streams collected over the lifetime of the pigs is the essence of the whole-herd epidemiological analysis investigation. This approach is even more important when investigating risk factors associated with swine wean-to-finish (W2F) mortality because of its multicausal and dynamic nature of mortality. The objective of this study was to use a retrospective dataset ("master table") containing information on 1,742 groups of pigs marketed over time to identify the major risk factors associated with W2F mortality. The master table was built by combining historical breed-to-market performance and health data with disease diagnostic records (Dx Codes) from marketed groups of growing pigs ("closeouts"). After building the master table, univariate analyses were conducted to screen for risk factors to be included in the initial multivariable model. After a stepwise backward model selection approach, 5 variables and 2 interactions remained in the final model. Notably, the only disease diagnosis variable significantly associated with W2F mortality was porcine reproductive and respiratory syndrome virus (PRRSV). Closeouts with reported clinical signs suggestive of Salmonella spp. and/or Escherichia coli infection were also significantly associated with higher W2F mortality. Source sow farm factors that remained significantly associated with W2F mortality were the sow farm PRRS status at the time of weaning, average weaning age, and the average pre-weaning mortality. Two interactions were significantly associated with wean-to-finish pig mortality: 1) sow farm PRRS status and a laboratory diagnosis of PRRSV and 2) average weaning age and a laboratory diagnosis of PRRS. Closeouts originating from PRRS epidemic or PRRS negative sow farms, when diagnosed with PRRS in the growing phase, had the highest W2F mortality rates. Likewise, PRRS diagnosis in the growing phase was an important factor in mortality, regardless of the average weaning age of the closeouts. Overall, this study demonstrated the utility of a whole-herd approach when analyzing diagnostic information along with other breeding-to-market productivity and health factors, to measure the major risk factors associated with W2F mortality in specified time frames and pig populations.