Effect of Dietary Source and Concentrations of Copper, Manganese, and Zinc on Growth Performance and Immune Response of Nursery Pigs Following an Acute Lipopolysaccharide Challenge

Trace minerals play an important role in immune system function; however, data regarding the effect of source (bioavailability) and low concentrations of Cu, Mn, and Zn on the immune response are lacking. Therefore, the objective was to evaluate dietary source and concentrations of Cu, Mn, and Zn on growth performance and immune response of nursery pigs following an acute immune challenge. An experiment utilizing 560 pigs (10 pigs/pen, 56 pens) was performed. Pens were randomly allotted based on BW to one of four dietary treatments (14 replicates/trt). The dietary treatments were the combination of low (5 ppm Cu, 16 ppm Mn, and 50 ppm Zn) vs. typical (10 ppm Cu, 32 ppm Mn, and 100 ppm Zn) concentrations added as either sulfate or hydroxychloride sources. Pigs were fed representative, fortified nursery diets in three phases: N1, d 0-7, (common diet); N2, d 7-22; N3, d 22-42. Trace minerals were added to the common basal diet in N2 and N3 phases to provide the 4 dietary treatments. Pigs and feeders were weighed to calculate ADG, ADFI, and G:F. On d 21, four pigs per pen received an intraperitoneal injection of LPS (25 µg/kg BW) to stimulate an acute immune response. Body weight, rectal temperature, and blood samples were taken prior to the injection and 3 h afterwards. Serum was analyzed for TNF-α and IL-1 β by ELISA. Data were analyzed as a 2x2 factorial arrangement (concentration, source, and concentration x source interaction). Overall (d 0-42), BW, ADG, ADFI, and G:F were not affected (P > 0.10) by dietary treatment. Pigs fed hydroxychlorides had a numerically (P = 0.12) lower increase in rectal temperature and had lower (P = 0.04) BW loss 3 h following the LPS injection. There was no effect (P > 0.10) of dietary treatment on TNF-α or IL-1β at h 0 (pre-injection). At 3 h post-injection, the increase in TNF-α and IL-1β was blunted (P < 0.03) for pigs fed hydroxychlorides (6603 vs. 8176 pg TNF-α/mL; 321 vs. 463 pg IL-1β/mL). Also, pigs fed typical mineral concentrations had a smaller increase (P < 0.07) in cytokines vs. pigs fed the lower concentrations (6737 vs. 8042 pg TNF-α /mL; 462 vs 324 pg IL-1β/mL). These results suggest that replacing sulfate minerals with hydroxychloride sources mitigated the acute immune response by decreasing proinflammatory cytokine production, possibly suggesting greater bioavailability over sulfate sources.