Abstract Anemia is increasingly recognized as common and consequential in prolific sows. Although dietary iron often exceeds estimated requirements, its bioavailability is constrained by mineral antagonism, phytate, and regulated intestinal uptake. Parenteral iron may provide a more effective strategy to prevent or correct deficiency. This study aimed to evaluate the hematological and biochemical responses of post-weaning sows to two intramuscular doses of iron dextran over a 30-day period. Twenty weaned sows (PIC: Camborough) were allocated by parity, body weight, and initial blood hemoglobin (Hb) and assigned to one of three treatments (n = 6–7 per group): 0 mg (CONFe), 2,500 mg (MODFe), or 5,000 mg (HIGHFe) of intramuscular iron dextran. All sows were fed a corn–soybean meal-based gestation diet once daily (2.2 kg/sow), which met or exceeded requirements for pregnant gilts and contained 165 mg/kg supplemental iron from ferrous sulfate monohydrate. Iron dextran injections were administered on day 1 post-weaning. Blood Hb was measured every other day from day 0 through day 30 using the HemoCue Hb 201+ analyzer. Blood samples for serum iron parameters were collected via jugular venipuncture on days 0 (pre-injection) and 30 of gestation. Sow body weight was also recorded on days 0 and 30 of gestation. Data were analyzed using PROC GLIMMIX with treatment, day, and their interaction as fixed effects on sow blood markers. No adverse effects were observed with iron treatment, indicating that intramuscular iron dextran is well tolerated in sows. Mean blood Hb over the 30-day period was higher in both the MODFe and HIGHFe groups compared with the CONFe group (CONFe: 10.3 g/dL; MODFe: 11.4 g/dL; HIGHFe: 11.2 g/dL; P = 0.005), with no difference between MODFe and HIGHFe, suggesting that a moderate dose is sufficient to improve circulating Hb. Serum ferritin increased from day 0 to 30 in the MODFe group (10.6 → 36.8 ng/mL; P = 0.019) and tended to increase in the HIGHFe group (10.5 → 38.3 ng/mL; P = 0.057), while no significant change occurred in the CONFe group (10.1 → 31.1 ng/mL; P = 0.130), indicating that parenteral iron supplementation improved iron stores. Total iron-binding capacity declined from day 0 to 30 in all groups (P 0.001), consistent with physiological changes in iron transport during early gestation. Serum iron concentrations remained stable across time and treatments (82–92 µg/dL), highlighting that circulating iron is tightly regulated and may not fully reflect improvements in iron status. In conclusion, post-weaning intramuscular iron dextran improved Hb and ferritin in post-weaned sows. Further research is needed to evaluate long-term effects on blood health and reproduction, as well as the feasibility and return on investment of implementing iron dextran on a larger scale in sow herds.
McClellan et al. (Wed,) studied this question.