Iron balance during gestation: benefits and risks of iron supplementation in sows

Pregnant sows are often affected by iron deficiency, but excessive iron supplementation may also be harmful. Too much iron can accumulate in tissues and trigger cellular damage through oxidative stress and ferroptosis, a form of cell death associated with lipid peroxidation.

Objective: Therefore, this study aimed to identify the optimal iron supplementation dose for gestating sows and investigate the mechanisms underlying iron deficiency and overdose, which contribute to reduced reproductive performance in sows.

Methods: In this study, 84 pregnant sows with similar farrowing times were divided into three dietary groups: a low-iron basal diet (L-Iron), a diet supplemented with a moderate level of protein-bound iron (N-Iron; 0.13%), and a diet supplemented with a high level of protein-bound iron (H-Iron; 0.27%).

Results: Moderate iron supplementation produced the best reproductive outcomes. Sows in the N-Iron group had a higher number of live-born piglets and improved placental vascular development compared with both the low-iron and high-iron groups. These findings suggest that an adequate iron supply supports nutrient and oxygen exchange between the sow and the fetuses during gestation. In contrast, excessive iron supplementation appeared to promote iron accumulation in the placenta. The H-Iron group showed reduced expression of proteins involved in iron transport, such as transferrin and transferrin receptor 1, alongside increased levels of ferritin and nuclear receptor coactivator 4, which are associated with iron storage and recycling. This group also exhibited higher expression of inflammatory and lipid peroxidation markers, indicating oxidative damage and mitochondrial dysfunction.

Conclusion: Overall, the study suggests that moderate iron supplementation in iron-deficient pregnant sows can improve placental development and increase piglet survival. However, excessive iron supplementation may have the opposite effect, leading to placental iron overload, oxidative damage, and ultimately fewer live-born piglets.