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 [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. Iron deficiency is one of the most common issues in newborn piglets and can impair growth and overall health before and after weaning. This study evaluated how different iron injection frequencies (no, one, or two injections of 200 mg iron) during the suckling period influenced pre- and post-weaning growth, hemoglobin levels, antioxidant status, and whole-body iron retention in piglets from two sire lines. Increasing number of iron injections improved pre- and post-weaning growth performance with the greatest weaning weight and growth rate observed in piglets that received two injections. They maintained higher hemoglobin levels from d 15 of age through d 14 postweaning. Increasing iron injection frequency led to increased iron retention in organs and the whole body, confirming that the administered iron was effectively stored. Antioxidant capacity was enhanced with the additional iron injection. Piglets with no iron injection had iron deficiency anemia, resulting in reduced growth, lower iron retention, and decreased antioxidant capacity. However, hemoglobin levels recovered after 4 wk in the nursery. Although differences were observed in growth and hemoglobin levels between the two sire lines, whole-body iron retention was similar. Overall, administering a second iron injection before weaning improved growth, hemoglobin levels, antioxidant capacity, and iron stores in piglets.