Effect of second iron injection on growth performance, hematological parameters, and fecal microbiome of piglets fed different dietary iron levels

This experiment was conducted to evaluate the effects of a second iron injection for suckling pigs fed diets with different dietary iron levels in the nursery period on growth performance, hematological parameters, serum and liver trace mineral content, fecal score, microbiome, and metabolites. A total of 70 newborn pigs from 7 litters were assigned to either 1 or 2 iron injections within the litter and received the first i.m. iron injection (200 mg) at 2 to 3 d of age. Pigs assigned to the second injection treatment received an additional iron injection 5 d after the first injection. At weaning (days 27 to 30 of age), pigs within iron injection treatments were divided into 2 nursery diet treatments for a 27-d growth period. Treatments were 1) no additional iron injection + nursery diets with 100 ppm iron (NC), 2) second i.m. iron injection (200 mg) + NC diets, 3) no additional iron injection + nursery diets with 200 ppm iron (PC), and 4) second i.m. iron injection (200 mg) + PC diets. The second iron injection increased liver iron content at weaning (P = 0.08, tendency), and serum iron, hemoglobin, and hematocrit levels until day 13 postweaning (P