Effects of Different Sources of Iron on Growth Performance, Immunity, and Intestinal Barrier Functions in Weaned Pigs

To explore the effect of different sources of iron on growth performance and intestinal health, 24 weaned pigs were randomly allocated to three groups and fed with a basal diet (BD) or BD containing 100 mg/kg ferrous sulfate (FS) or ferrous glycine (FG). The trial lasted for 21 d, and blood and tissue were collected for analysis. Results showed that FG significantly decreased the feed-to-gain ratio and increased the iron content in the liver and tibia (<i>p</i> < 0.05). Both FS and FG elevated bladder and fecal iron content and significantly elevated the contents of red blood cells, hemoglobin (HGB), and ferritin in the blood (<i>p</i> < 0.05). FG supplementation increased the serum concentrations of immunoglobulin (Ig) G and IgM, but decreased the concentrations of D-lactate and endotoxin (<i>p</i> < 0.05). Interestingly, FG significantly increased the villus height and the ratio of villus height to crypt depth (V/C) in the duodenum and ileum (<i>p</i> < 0.05). FG supplementation also increased the abundance of tight-junction protein ZO-1 but significantly decreased the rate of apoptosis in the jejunum (<i>p</i> < 0.05). Moreover, the activities of jejunal sucrase, maltase, and catalase (CAT) in the FG group were higher than that in other groups (<i>p</i> < 0.05). Importantly, FG not only elevated the expression levels of cationic amino acid transporter-1 (CAT1) in the duodenal and jejunum but also elevated the expression levels of glucose transporter-2 (GLUT2) and sodium/glucose co-transporter 1 (SGLT1) in the ileum (<i>p</i> < 0.05). These results indicated that appropriate iron supplementation is beneficial to piglet intestinal health by enhancing immunity and improving antioxidant capacity, and FG may serve as an efficient substitute for conventionally used iron sources.