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

A total of 156 newborn piglets from 15 sow litters (initial body weight [BW] of 1.75 ± 0.38 kg at d 3 of age; seven from PIC337 and eight from PIC800 sire lines, all bred to Camborough sows) were allotted to six treatments in a 2 × 3 factorial arrangement. Main factors were: 1) sire line (PIC337 vs. PIC800), and 2) number of iron injections (no, one, or two 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 six 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 pre-weaning performance between two sire lines, PIC337 pigs tended to have greater overall nursery feed intake (P = 0.10) and BW 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 BW 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 post-weaning 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.