Effects of dietary inorganic and organic iron sources on maternal and piglet iron status across one complete reproductive cycle in highly prolific sows.

Abstract

Ferrous sulfate (FeSO₄) is commonly used in swine diets, yet sow anemia remains prevalent, prompting the need to evaluate alternative iron sources. This study evaluated polysaccharide complexed iron (PC-Fe; non-heme organic iron source) and spray-dried bovine blood cells (HEME-Fe; heme-organic iron source) as alternatives to FeSO₄ (CON-Fe; inorganic iron source) on sow and offspring iron status. At 2 ± 1 d of gestation, 44 female pigs were allocated by parity (0 to 4), body weight, and initial blood hemoglobin (Hb) to one of three dietary iron treatments: a control group (CON-Fe) receiving 125 mg/kg of iron from FeSO₄ monohydrate (n = 15), a non-heme organic iron group (PC-Fe) receiving 125 mg/kg iron from a polysaccharide-complexed iron source (n = 15), and a heme iron group (HEME-Fe) receiving equal amounts of Fe from FeSO₄ and organic heme iron from spray-dried red blood cells (RBCs) (n = 14). Sows were fed their assigned diets until weaning, meeting or exceeding the estimated nutrient requirements for gilts during both gestation and lactation. Sow blood was collected on days 0, 30 ± 2, 60 ± 2, 90 ± 2, and 110 ± 2 of gestation, and at weaning (day 18 ± 3 of lactation). In piglets, Hb was measured within 12 hours after birth and at weaning (day 18 ± 3) using a point-of-care analyzer (HemoCue 201+). Additionally, four piglets per litter were sampled at birth and two at weaning for serum analyses via jugular puncture. Sow and piglet serum samples were analyzed for serum iron (SI), ferritin (SF), and total iron-binding capacity (TIBC). Sow whole blood was also analyzed for hematological parameters including white blood cells, RBC, Hb, packed cell volume, and platelet counts. On day 90 of gestation, sows supplemented with HEME-Fe had higher Hb concentrations (12.1 g/dL) compared to those receiving CON-Fe (10.9 g/dL) and PC-Fe (10.8 g/dL) (P = 0.001). On day 30, PC-Fe sows had higher SF concentrations (21.4 ng/mL) than CON-Fe sows (10.4 ng/mL; P = 0.027), with HEME-Fe sows showing intermediate values (15.4 ng/mL). The PC-Fe sows also tended to have lower TIBC (576.7 µg/dL) than CON-Fe sows (613.1 µg/dL; P = 0.059), with HEME-Fe again being intermediate (600.4 µg/dL). Piglet anemia at birth (Hb < 10 g/dL) was lowest in PC-Fe (29%), followed by HEME-Fe (42%), both lower than CON-Fe (75%) (P < 0.001). PC-Fe improved early maternal iron storage, while HEME-Fe supported late gestational Hb, both enhancing neonatal iron status compared to FeSO₄.