Effects of second iron injection before weaning on growth performance, hematological parameters, fecal score, and microbiome of pigs fed nursery diets with different dietary iron levels under natural disease challenge

     

This study was conducted to demonstrate the effects of second iron injection before weaning and iron levels in nursery diets on growth performance, hematological parameters, and fecal microbiome of pigs. A total of 70 newborn pigs from 7 sows were allotted to 4 treatments within litter, housed in farrowing crate without creep feed, and received the first dose (200 mg iron) at 2 to 3 d of age. At weaning (d 27–30 of age), all pigs were housed in nursery pens within their original treatments for a 27-d growth period and naturally challenged with Escherichia coli and rotavirus. Treatments were as follows: (1) NC: no additional iron injection and supplementation (100 ppm iron in the basal diets); (2) NC+IRON: second iron injection (200 mg) at least 5 d after first injection + NC diets; (3) PC: additional 100 ppm iron supplementation; and (4) PC+IRON: second iron injection (200 mg) + PC diets. A common iron-dextran product (UNIFERON®200, Pharmacosmos Inc.) was used for both i.m. injections. Fecal microbiome composition was analyzed using amplicon sequencing targeting the V1–V9 regions of the 16S rRNA gene. Second iron injection increased hemoglobin (HG; 9.92 vs. 11.45 g/dL), hematocrit (HCT), and serum iron (P < 0.05) levels until d 13 postweaning. Second iron injection increased body weight at d 27 postweaning (P = 0.05, 18.8 and 20.8 kg), overall growth rate (P = 0.08), and feed intake (P < 0.05) but reduced overall fecal score. The ANCOM showed a higher abundance of the bacterial taxon Lactobacillales in the 2-injection group than in the 1-injection group at weaning. The pigs fed the PC diets had greater HG and HCT levels (P < 0.05) at d 27 postweaning and lower fecal score (P = 0.09; tendency) from d 13 to 27 postweaning than the NC diets. The second iron injection to pigs before weaning could improve postweaning hematological parameters and growth performance, reduce fecal score, and affect fecal microbiome, whereas 100 ppm of dietary iron supplementation increased hematological parameters and reduced fecal score in the late nursery period.

Key Words: Iron, second injection, dietary iron level, fecal microbiome, pigs.