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

Authors: JOHNSON, ALAINA - University Of Wisconsin; Li, Wenli; DITTRICH, BARBARA - University Of Wisconsin; COLE, ALEAH - University Of Wisconsin; PRODELL, MARIE - University Of Wisconsin; FRITZ, SCOTT - Kansas State University; FREGULIA, PRISCILA - Oak Ridge Institute For Science And Education (ORISE); CHEN, CHI - University Of Minnesota; KOWN, CHANHO - University Of Georgia; JANG, DAL - University Of Georgia

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/6/2024
Publication Date: 12/7/2024
Citation: Johnson, A., Li, W., Dittrich, B., Cole, A., Prodell, M., Fritz, S., Fregulia, P., Chen, C., Kown, C., Jang, D.Y. 2024. Effect of second iron injection on growth performance, hematological parameters, and fecal microbiome of piglets fed different dietary iron levels. Journal of Animal Science. https://doi.org/10.1093/jas/skae371.
DOI: https://doi.org/10.1093/jas/skae371

Interpretive Summary: Iron deficiency is the most prevalent disorder in pigs during the early post-natal period. This study evaluated the effects of a second iron injection given to suckling pigs at 7-8 d of age after receiving an initial injection at 2-3 d of age and fed diets containing two different dietary iron levels in the post-weaning nursery period on growth, hematological characteristics, serum and liver trace minerals, and fecal microbiome. Results showed that the second iron injection to suckling pigs increased liver iron content at weaning, increased hemoglobin and serum iron levels until the early nursery period and improved overall growth performance of nursery pigs. The high dietary iron level increased hemoglobin levels at the end of the study but had no effect on growth. The fecal microbiome diversity was influenced by both iron injection and dietary iron level. The results suggest that the second iron injection to suckling pigs could enhance postweaning growth performance by improving hematological characteristics and altering fecal microbiome regardless of dietary iron level.

Technical Abstract: Iron deficiency is the most prevalent disorder in pigs during the early post-natal period. 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 serum metabolites. A total of 70 newborn pigs from 7 litters were assigned to either one or two iron injections within litter and received the first i.m. iron injection (200 mg) at 2-3 d of age. Pigs assigned to the second injection treatment received an additional iron injection 5 d after the first injection. At weaning (d 27-30 of age), pigs within iron injection treatments were divided into 2 nursery diet treatments for a 27-d growth period for a total of four treatments. Treatments were: 1) no additional iron injection + nursery diets with 100 ppm iron (NC), 2) a 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 d 13 postweaning (P < 0.05). In the nursery period, pigs receiving the second iron injection had a greater final body weight (P = 0.08, tendency), overall growth rate (P = 0.08, tendency) and feed intake (P < 0.05), and lower fecal score (P < 0.05) indicating firmer feces compared to those receiving one iron injection. There was no major effect of dietary iron level or interaction with the iron injection treatment in any measurements except that the pigs fed the PC diets had greater hemoglobin and hematocrit levels (P < 0.05) at d 27 postweaning and a lower fecal score (P = 0.08, tendency) in the late nursery period than those fed the NC diets. The second iron injection reduced fecal bacterial alpha-diversity based on Faith’s phylogenetic diversity at weaning (P < 0.05), while the second iron injection and dietary iron levels resulted in dissimilarity in the fecal bacterial community based on Unweighted Unifrac analysis (P < 0.05; at weaning by iron injection and d 27 postweaning by dietary iron level). In conclusion, the second iron injection for suckling pigs improved postweaning growth performance and hemoglobin levels and affected the fecal microbiome, whereas an additional 100 ppm of dietary iron supplementation increased hemoglobin levels and altered the fecal microbiome in the late nursery period but did not affect postweaning growth.