PSI-9 - Impacts of Formic Acid and Glycerol Monolaurate on Weanling Pig Immune Function

Abstract: Feed additives such zinc oxide (ZnO) reduce post-weaning diarrhea and improve nursery pig growth performance, but there is regulatory pressure to eliminate their inclusion due to environmental concerns. Dietary acidifiers have been shown to positively impact gut health, immune status, and performance post-weaning. The objective of this experiment was to evaluate the effects of feeding formic acid and/or glycerol monolaurate (GML) on immune status of nursery pigs. A total of 350 weanling pigs (DNA 200 × 400; 5.7 ± 0.06 kg BW) were fed for 42 days with 5 pigs/pen and 14 pens/treatment. Pens were assigned in a completely randomized design to one of five diets: 1) Negative control (no additives); 2) Control + 3,000 ppm ZnO in phase 1 and 2,000 ppm ZnO in phase 2; 3) Control + 0.7% formic acid; 4) Control + 0.18% GML; 5) Control + 1.0% blend of formic acid and GML. Blood samples were collected via the jugular vein on d 0 and d 14 from 1 randomly selected pig per pen (14 pigs/treatment; 70 pigs total) for analysis of serum immunoglobulins (IgA, IgG) and tumor necrosis factor-α (TNF-α). After collection, samples were centrifuged at 2000 x g for 10 min at 4°C and recovered serum was stored at -20°C until analysis. Using an ELISA kit, IgA, IgG and TNF- α were measured according to the kit manufacturer’s recommendations. Data were analyzed using the GLIMMIX procedure of SAS, with pig as the experimental unit. There was no evidence of differences (P > 0.05) in serum IgA, IgG, or TNF-α as a result of dietary treatment. Sampling day significantly impacted (P < 0.05) both serum IgA and IgG concentrations, where regardless of treatment, the levels of IgA increased from d 0 to 14 and decreased for IgG. In summary, feeding formic acid and/or GML did not impact serum immunoglobulin or cytokine levels. Further investigation into how these acidifiers effect immune function post-weaning is needed.