Simple SummaryPotassium and magnesium trace minerals play a critical role in the biological metabolic functions of livestock. This study was undertaken to investigate the effects of dietary supplementation with different types of potassium and magnesium, synthetic (magnesium sulfate and potassium chloride) or natural (potassium-magnesium sulfate), on the reproductive performance, antioxidant capacity, and immunity of sows. We found that dietary supplementation with natural potassium and magnesium during late gestation could enhance sows’ antioxidant capacity and the immunoglobulin A level in colostrum. Compared with the synthetic potassium and magnesium, the natural potassium and magnesium functioned better, reflected by potentially mitigating the incidence of intrauterine growth restriction of piglets and decreasing the concentration of the proinflammatory cytokine level in plasma. These findings have important implications for the application of magnesium and potassium trace minerals in sow production to improve reproductive performance.AbstractThe objective of this study was to investigate the effects of dietary supplementation with different types of potassium and magnesium on the reproductive performance, antioxidant capacity, and immunity of sows. Forty-five Landrace × Yorkshire sows at the late gestation stage (85 d) were randomly assigned to three groups (n = 15). Sows in the control group (CON), potassium chloride and magnesium sulfate group (PM), and potassium-magnesium sulfate group (PMS) were fed with a basal diet, a basal diet supplemented with magnesium sulfate (0.20%) and potassium chloride (0.15%), or a basal diet supplemented with potassium-magnesium sulfate (0.45%), respectively. The results showed that dietary supplementation with PMS did not yield significant effects on the reproductive performance compared with the CON group (p> 0.05). However, it significantly elevated the level of insulin-like growth factor 1 (IGF-1) in plasma and immunoglobulin A (IgA) in colostrum (p< 0.05). Furthermore, PMS significantly augmented the activities of catalase (CAT) and superoxide dismutase (SOD) while reducing the levels of malondialdehyde (MDA) in comparison to the CON group (p< 0.05). Compared with the PM group, the PMS group significantly reduced the incidence rate of intrauterine growth restriction (IUGR) (p< 0.05) and significantly decreased the concentration of the proinflammatory cytokine (TNF-α) level in plasma (p< 0.05). These results indicated that dietary supplementation with PMS during late gestation could enhance sows’ antioxidant capacity and the IgA level in colostrum. These findings will provide a theoretical reference for the use of magnesium and potassium in sow production to improve sows’ health.