Defining resilient pigs after a Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) challenge using activity and feeding data from accelerometers

Porcine reproductive and respiratory syndrome (PRRS) is an infectious viral disease in pigs. PRRS causes reproductive failure in sows and respiratory infections in growing pigs. To improve pig health and minimise economic losses, resilient pigs are preferred within the herd. Resilient pigs still become infected, yet are able to recover following infection, showing less variation in activity and feeding. In this study, 232 commercial crossbred pigs were equipped with individual accelerometer ear tags to monitor the number of active, feeding, and hyperactive events per individual per hour. At eight weeks of age, pigs were inoculated with PRRS virus 1-7-4. Data from accelerometers were collected 23 days prior to challenge and 42 days post-infection (dpi). Expected levels of activity, feeding, and hyperactivity were estimated by regressing behavioural traits on observed datapoints prior to challenge. This regression line was extended to 42 dpi. Then, deviations from the regression line were quantified as Root Mean Square Error (RMSE) for each individual during the following time periods: pre-challenge, 0-13 dpi, and 13-42 dpi. All traits decreased and RMSE increased post-challenge. These results are consistant with clinical signs of PRRS, including lethargy and loss of appetite. In addition, association of these traits with survival was also investigated. RMSE prior to PRRS-infection was not predictive of survival after infection. However, RMSE of feeding and activity during the peak challenge period (0-13 dpi) was predictive of survival, where pigs with less deviation in behaviour were more resilient to the PRRS challenge.