Introduction/Background
Early recognition and confirmation of disease outbreaks are critical for timely implementation of intervention strategies aimed at reducing associated morbidity, mortality, and production losses in commercial swine systems. Traditional indicators, including clinical signs, mortality, and individual treatments, are often lagging indicators that occur after disease circulation is established within a population. In contrast, changes in water intake may serve as an earlier, leading indicator of health challenges. Water disappearance is routinely monitored through barn controller systems and may serve as a proxy for identifying potential disease breaks within a population. Therefore, the objective of this study was to evaluate changes in water consumption associated with disease outbreaks and characterize the magnitude of water intake reductions observed during confirmed porcine reproductive and respiratory syndrome virus (PRRSV) and influenza outbreaks in commercial wean-to-finish barns.
Materials and Methods
Retrospective production, water consumption, environmental, and health-related data were compiled from commercial wean-to-finish barns at the room level, with the room serving as the observational unit. Data encompassed approximately 55,000 pigs across 23 production turns over a four-year period. Daily water disappearance (gallons/room) was collected from barn controller systems at approximately the same time each day and evaluated relative to days on feed.
A healthy baseline period prior to outbreak recognition was utilized to establish expected water disappearance patterns. Water disappearance trends were assessed using an exponentially weighted moving average (EWMA), with upper and lower monitoring thresholds generated using ±0.5 standard deviations in R. Thresholds were selected to improve sensitivity for identifying biologically meaningful deviations in water disappearance patterns. When reductions in water disappearance below thresholds were identified, associated diagnostic and production-related events (e.g., marketing, pig movements, or equipment issues) were evaluated descriptively. Temporal relationships between water intake reductions and lagging indicators, including individual treatments and mortality, were also assessed. Disease outbreaks were classified based on clinical presentation and laboratory diagnostic confirmation. For confirmed outbreaks, percentage reductions in water intake and time-to-detection relative to other indicators were summarized.
Results
Reductions in water disappearance commonly preceded other indicators, such as mortality and number of daily individual treatments. In representative outbreak events, increases in individual treatments occurred approximately 6 days following reductions in water intake, while increases in mortality occurred approximately 9 days later.
The median reduction in water disappearance associated with confirmed lateral PRRSV outbreaks was 22%, while the median reduction associated with influenza outbreaks was 14%. Overall, findings suggest that approximately a 20% reduction in water intake may serve as a leading indicator of disease outbreaks in commercial wean-to-finish populations.
Discussion and Conclusion
Results from this investigation suggest that reductions in water intake may serve as an early and objective indicator of disease outbreaks in commercial swine systems. Reductions in water disappearance preceded increases in individual treatments and mortality, suggesting water intake monitoring may aid in earlier recognition of health challenges. However, water intake data should be interpreted alongside management and environmental factors that may influence water disappearance patterns. Additional investigation evaluating sensitivity, specificity, positive predictive value, and negative predictive value is needed to further characterize the predictive performance of water intake monitoring for disease outbreak detection. Overall, these findings support the potential utility of water disappearance monitoring as an early surveillance indicator in commercial swine barns.