269 Evaluation of changes in the activity of group-housed nursery pigs exposed to an endotoxin challenge using the NUtrack Livestock Monitoring System

Abstract The objective of this study was to evaluate the changes in activity of group-housed, newly weaned, Duroc-sired crossbred commercial pigs exposed to a lipopolysaccharide (LPS) challenge. At weaning, pigs [n = 192, body weight (BW) = 5.73 ± 1.8 kg] were stratified by sex, litter, and weaning weight and randomly assigned to one of three treatment groups (16 pigs/pen, 4 pens/treatment). Treatments were: 1) control – saline-injected (SAL), 2) 50% challenged (LPS50) – one-half of the pigs in a pen (n = 8) were challenged with LPS, the remaining 8 pigs received saline, and 3) 100% LPS challenged (LPS100) – all pigs in a pen were challenged with LPS. Pigs in the SAL group and 32 in the LPS50 group received a 3.0 mL subcutaneous saline injection. The remaining pigs in the LPS50 group and all pigs in the LPS100 group received a 3.0 mL subcutaneous LPS (E. coli O111:B4) injection dissolved in sterile saline calculated to challenge each pig with 300 µg/kg of BW. Pigs were continuously monitored (24 h/d) during the 42-d nursery period via the NUtrack Livestock Monitoring System. Activity traits included distance traveled (m/d), time spent at the feeder (% of day), and time spent standing (% of day) and were analyzed using the PROC GLIMMIX procedure of SAS. When main effects or interactions were significant (P ≤ 0.05), specific comparisons were made using the PDIFF option in SAS. Changes in activities were observed (P ≤ 0.03) in both LPS groups for the first 3 to 4 d after the challenge. During this period, pigs in the LPS50 and LPS100 groups walked less (P ≤ 0.001) and spent less (P ≤ 0.002) time standing and less (P ≤ 0.03) time at the feeder when compared with pigs in the SAL group. By d 5, activities were similar (P ≥ 0.07) between the three treatment groups and remained similar (P ≥ 0.38) until 9 d after the LPS challenge. Starting on d 11 and continuing until d 15, there was an increase (P ≤ 0.03) in both meters walked/d and time spent standing for pigs in the LPS100 group compared with the SAL group. Furthermore, on d 10 to 15, pigs in the LPS50 and LPS100 groups spent more (P ≤ 0.05) time at the feeder when compared with the pigs in the SAL group. However, increased time at the feeder from d 9 to 15 for LPS100 did not offset the impact of the LPS challenge on nursery exit weight. At exit (d 42), pigs in the LPS100 group had reduced (P ≤ 0.04) BW and average daily gain, when compared with the pigs in the SAL group. Overall, these results suggest that changes in activities following an LPS challenge are not limited to the days immediately following the challenge. Although an LPS challenge elicits a short-lived (3 - 4 d) immune response, its effects can be long-lasting.