500 Effect of different iron sources on growth performance, gut health, and microbiota in nursery pigs

Abstract This study evaluated the effect of different iron sources, including iron polysaccharide complexes (SQM iron) and ferrous sulfate (FS) on growth performance, gut health, pathogenic bacteria load, colon fecal microbiota, and fecal iron concentration in nursery pigs. Nursery pigs (n = 320, TN70 cross, Topigs Norsvin Canada) weaned at 21 ± 2 d were randomly assigned to four treatments arranged in 2 x 2 factorial, with the factors being sanitation conditions (clean vs. dirty) and iron sources (SQM iron vs. FS, each at 100 mg iron/kg) to give 8 pens (10 piglets per pen) per treatment. Pigs were fed their respective diets in two phases over a 28-d period. Fecal scores, body weight (BW) and feed intake were recorded weekly. Iron content, gene expression of butyryl-CoA:acetate CoA-transferase and bisulfite reductase, and pathogenic bacteria counts were determined in fresh fecal samples collected on d 0, d 14, and d 21. On d 28, one pig randomly selected from each pen was euthanized to sample colon digesta for microbiota analysis and jejunal tissue and serum for gut integrity and permeability analysis. Data were analyzed using PROC MIXED of SAS followed by Tukey’s multiple comparison test except for raw 16s sRNA sequences, which were processed using QIIME2 and analyzed with Kruskal-Wallis test. Overall, from d 0 to14 SQM iron resulted in higher average daily gain (ADG) and average daily feed intake (ADFI; P < 0.05). SQM iron resulted in higher fecal iron at d 21 and improved fecal scores at d 27 (P < 0.05). SQM iron increased the relative abundance of fecal Campylobacter jejuni when comparing d 21 to d 0, and O157 E. Coli when comparing d 14 to d 0 (P < 0.05). Ferrous sulfate resulted in greater changes in relative abundance of butyryl-CoA:acetate CoA-transferase and bisulfate reductase than the SQM iron treatment under clean conditions when comparing d 21 to d 0 (P < 0.05). Dietary iron treatments did not significantly affect gastrointestinal integrity and permeability in jejunum and did not alter fecal microbiota composition on d 28. In conclusion, substituting 100 mg/kg added iron as FS with equal concentration of SQM iron improved ADG in the initial 2 wk and overall ADFI and promoted gut health indicators.