Abstract
This study aimed to investigate the effects of iron, vitamin A (VA) and their interaction on intestinal development and differentiation of cells in suckling piglets. Therefore, 32 Duroc × Landrace × Yorkshire 0-day-old newborn boars with similar body weights were randomly divided into 4 groups, with 8 replicates in each group and 1 pig in each replicate. All the piglets were breastfed. In addition, the piglets were given normal saline (CON group) or ferrous sulfate (OAFe group) or VA (VA group) or ferrous sulfate and VA (OAFe + VA group) on the 2 nd, 7 th, 12 th and 17 th day, respectively. The piglets were then slaughtered on the 21 st day, and intestinal samples were collected. The results showed that: (1) iron (P < 0.001) significantly increased the length, weight, relative weight, and the length to weight ratio of the small intestine. On the other hand, VA had a significant effect on the weight to length ratio (P = 0.015) and relative weight (P < 0.001) of the small intestine; (2) with regard to intestinal morphology, supplementation with iron (P <0.05) had obvious effects on the villus height (VH), crypt depth (CD), villus width (VW), and surface area. Additionally, both VA and interaction of VA and iron increased the VH (P < 0.05) and surface area (P = 0.001). The results also showed that iron (P < 0.01) increased the number of crypt goblet cells, Ki67 positive cells, and endocrine cells. Moreover, both VA and the interaction between VA and iron increased the number of endocrine cells in the villi (P = 0.05); (3) With regard to the mRNA expression levels of stem cell differentiation marker genes, iron (P < 0.05) decreased the expression of trophinin 2 (Trop2), leucine rich repeat containing G protein-coupled receptor 5 positive (Lgr5+), male specific lethal 1(Msl1), BMI 1 proto-oncogene, polycomb ring finger (Bmi1), achaete-scute family bHLH transcription factor 2 (Ascl2). On the other hand, VA increased the expression of Ascl2 (P = 0.001) although the interaction of VA and iron (P < 0.05) had an effect on the expression of secreted phosphoprotein 1 (Spp1) and Bmi1. In addition, VA decreased the gene or mRNA expression of aconitase 1 (Aco1; P < 0.001), transferrin receptor (TFRC; P = 0.001), and solute carrier family 11 member 2 (DMT1; P = 0.003) in the Iron Reactive Element/Iron Regulatory Protein (IRE/IRP) signaling pathway although iron and the interaction of VA and iron had no effect on the genes’ expression. The results therefore showed that VA, iron, and their interaction can promote intestinal development and epithelial cell differentiation in piglets.