Comparison of ferrous sulfate, ferric ammonium citrate, and ferrous glycinate on growth performance, iron status, diarrhea incidence, and intestinal health in weaned piglets

Iron is an essential nutrient for piglets, although iron sources differ considerably in bioavailability and their effects on intestinal health are not fully understood.

Objective: The aim of this study was to compare the effects of ferrous sulfate (FeSO₄), ferric ammonium citrate (FAC), and ferrous glycinate (Fe-Gly) supplemented at 100 mg/kg on diarrhea incidence, growth performance, iron status, and intestinal health parameters in weaned piglets.

Methods: 21-day-old weaned piglets were used and randomly allocated into different dietary groups receiving FeSO₄, ferric ammonium citrate (FAC), or ferrous glycinate (Fe-Gly) at 100 mg/kg for 14 days. Growth performance, diarrhea incidence, and nutrient/iron status were evaluated throughout the experimental period. Blood parameters, intestinal health indicators, and gut microbiota composition were also assessed at the end of the trial.

Results: Compared with the FeSO₄ group, dietary supplementation with Fe-Gly increased body weight at day 35 and improved average daily feed intake and average daily gain during the 21–35 day period. In addition, Fe-Gly reduced the incidence of diarrhea. Although FAC also improved growth-related parameters, the effects were not markedly different from those observed with FeSO₄. Fe-Gly supplementation increased serum iron levels and total iron-binding capacity, while reducing iron content in colonic digesta. Both Fe-Gly and FAC improved antioxidant and anti-inflammatory status in piglets. Notably, Fe-Gly promoted an increase in the abundance of Lactobacillus while reducing the presence of potentially pathogenic bacteria such as Escherichia coli. Functional prediction analysis indicated that Fe-Gly supplementation was associated with an increased relative abundance of gut microbiota involved in carbohydrate metabolism and amino acid synthesis.

Conclusion: Overall, the results suggest that Fe-Gly improves systemic iron status, reduces excess intestinal iron, modulates gut microbiota composition, and enhances growth performance and intestinal health in weaned piglets, while lowering the incidence of diarrhea.