Continuous NU track monitoring revealed acute suppression and later changes in behavior after lipopolysaccharide challenge in nursery pigs

Abstract

This study evaluated changes in the active and resting behaviors of group-housed, newly weaned pigs challenged with lipopolysaccharide (LPS). At weaning (∼21 days of age), pigs (n = 192; 5.73 ± 1.8 kg) were stratified by sex, litter, and body weight and randomly assigned to 1 of 3 treatments (16 pigs/pen; 4 pens/treatment): 1) saline-injected control (SAL); 2) 50%-LPS, pens in which 8 of 16 pigs received LPS and 8 of 16 pigs received saline; or 3) 100%-LPS, pens in which all pigs received LPS. Following a 9-d acclimation period, assigned injections were administered on study day 10. Pigs in the SAL treatment group and 32 pigs in the 50%-LPS treatment group received a 3.0-mL subcutaneous saline injection. The remaining pigs in the 50%-LPS treatment group and all pigs in the 100%-LPS treatment group received a 3.0-mL subcutaneous LPS injection (Escherichia coli O111:B4; 300 µg/kg BW). Behavior was continuously monitored for 42 d using the NUtrack system to quantify meters walked, body revolutions, time spent standing, time at the feeder, time lying laterally and sternal, total time lying, and time sitting. During the LPS response period (days 10 to 13), pigs in the 100%-LPS and 50%-LPS treatment groups displayed a clear sickness-behavior response characterized by reduced activity and increased resting behavior (P ≤ 0.05). Compared with SAL, pigs in the LPS treatment groups walked fewer meters, completed fewer revolutions, spent less time standing and at the feeder, and spent more time lying and resting (P ≤ 0.05). At the end of the recovery period (day 19) and during the early post-recovery period, pigs in both LPS treatment groups walked more, completed more revolutions, and spent more time standing and at the feeder than pigs in the SAL treatment group (P ≤ 0.05). These later differences occurred primarily on study days 19 to 25, corresponding to 9 to 15 d after challenge. Despite these later increases in activity, pigs in the 100%-LPS treatment group had reduced nursery exit BW, reduced ADG, and less total weight gain than pigs in the SAL treatment group (P ≤ 0.05). These findings indicate that the behavioral response to LPS challenge extended beyond the LPS response period and included later changes in activity that were detected through continuous behavioral monitoring.