Effects of a second iron injection and sire line on growth performance, hemoglobin levels, antioxidative status, and whole-body iron retention in piglets

Abstract

A total of 156 newborn piglets from 15 sow litters (initial body weight of 1.75 ± 0.38 kg at d 3 of age; 7 from PIC337 and 8 from PIC800 sire lines, all bred to Camborough sows) were allotted to 6 treatments in a 2 × 3 factorial arrangement. Main factors were: 1) sire line (PIC337 vs. PIC800), and 2) number of iron injections (0, 1, or 2 intramuscular injections of 200 mg iron) administered at d 3 (one injection), or d 3 and 8 (two injections) of age. Six pigs per sire line at birth and 6 per treatment at weaning (d 18.9 ± 1.6 of age) were euthanized for various organs, whole blood and remaining body tissue collection for iron analysis. Remaining weaned pigs were transferred to a nursery facility and fed a common diet for 28 d. Growth performance, hemoglobin levels, antioxidant status, and iron retention were measured. Although there was no difference in preweaning performance between two sire lines, PIC337 pigs tended to have greater overall nursery feed intake (P = 0.10) and body weight at d 28 postweaning (P = 0.06) than PIC800 pigs. PIC337 pigs had lower hemoglobin levels than PIC800 pigs from d 15 of age to d 7 postweaning (P < 0.11), while no differences were observed in blood antioxidant parameters. Increasing iron injection frequency linearly increased body weight at weaning and d 28 postweaning and overall nursery weight gain (P < 0.05), while increasing hemoglobin levels linearly and quadratically from d 15 of age to d 14 postweaning (P < 0.05). Plasma malondialdehyde levels increased quadratically at weaning (P = 0.06) and d 14 postweaning (P < 0.05) with increasing iron injection frequency, while plasma catalase level increased linearly at d 14 postweaning (P < 0.05). Liver iron mass at birth was greater in PIC800 pigs than in PIC337 pigs (P < 0.05), while no differences were observed between sire lines in whole-body iron mass at birth and weaning, or in iron content of colostrum and milk. Total iron mass in individual organs and whole-body of pigs at weaning (P < 0.05) increased linearly with increasing iron injection frequency. In conclusion, increasing iron injection frequency before weaning improved pre- and postweaning growth, hemoglobin levels, plasma catalase levels, and whole-body iron retention, confirming that most of the injected iron was retained in the body, while hemoglobin levels were influenced by the sire lines without affecting overall body iron retention.