Effects of Oral Administration of Lipopolysaccharide on Growth Performance and Immune Response of Nursery Pigs

Intramuscular injection of lipopolysaccharides (LPS) from Escherichia coli is an accepted method of inducing inflammation and pro-inflammatory cytokine production in pigs at different stages of production. On the other hand, very limited data exists as to the efficacy of oral administration of LPS on immune function. Determination of successful delivery of LPS via feed or water would prove beneficial in a model of chronic immune challenge vs daily injections of LPS. Therefore, the objective of this research was to evaluate the effects of intramuscular and oral administration of LPS on growth performance and immune response in nursery pigs. Two hundred and eighty weaned pigs were blocked by BW and gender and housed 10 pigs per pen. Pigs were fed a common nursey diet. On d 18, pens were allotted to 5 treatments (5 reps/trt) consisting of intramuscular injection of saline or LPS (10 ug/kg BW; Escherichia coli O111:B4) and 3 doses of LPS administered via feed (15, 30 and 60 µg/kg BW of LPS O55:B5). Pigs were chronically challenged by LPS injection on d 18, 21, 23 and 25 (LPS dose increased by 12% each injection) and via feed daily from d 18-25. Body weight, rectal temperature, and blood samples were taken prior to the injection and 3 hours following the last dose. During this phase, IM LPS reduced (P < 0.05) ADG (379 vs. 446) and ADFI (555 vs. 651) vs. saline, and increased (P < 0.01) rectal temperature (48.1 vs 46.7 ^oC) and serum TNF-alpha (720 vs 129 pg/mL). Delivery of LPS via feed did not affect (P > 0.10) growth performance or immune response. On d 33, pigs that were previously administered LPS were injected with saline and vice versa for those administered saline. In addition, 2 doses (60 and 120 µg/kg BW) of LPS via water were administered. Pigs were chronically challenged by LPS injection on d 33, 35, 37 and 39 (LPS dose increased by 12% each injection) and via water daily from d 33-39. As shown during d 18-25, ADG and ADFI were numerically reduced, and temperature (47.2 vs 47.0 ^oC) and TNF-alpha (376 vs. 140 pg/mL) were increased (P < 0.05) by IM LPS vs. saline, but there were no effects (P > 0.10) of LPS via water. These data suggest that the orally deliveries of LPS used in this experiment were not effective in eliciting an immune response in nursery pigs.