Dietary Supplementation with 25-Hydroxyvitamin D3 on Reproductive Performance and Placental Oxidative Stress in Primiparous Sows during Mid-to-Late Gestation

The placenta plays a crucial role in nutrient transport and waste exchange between the dam and fetus, sustaining fetal growth. While the positive effects of 25-hydroxyvitamin D₃ (25-OH-D₃) on animal performance have been reported, its impact on placental function remains largely unknown. Therefore, this study aimed to investigate the effects of supplementing 25-OH-D₃ in the diet of primiparous sows on reproductive performance, antioxidant capacity, placental oxidative stress, nutrient transport, and inflammatory response during mid-to-late gestation. A total of 45 healthy Landrace × Yorkshire primiparous sows on day 60 of gestation were selected and randomly allocated to three treatment groups based on body weight and backfat thickness: the control group (corn-soybean meal basal diet), the VD₃ group (basal diet + 2000 IU VD₃), and the 25-OH-D₃ group (basal diet + 50 μg/kg 25-OH-D₃). The results demonstrated that supplementation with 25-OH-D₃ in the diet enhanced sows' average litter weight and birth weight during mid-to-late gestation. Additionally, plasma malondialdehyde (MDA) concentrations in sows significantly decreased in the VD₃ and 25-OH-D₃ groups (<i>p</i> < 0.05). Furthermore, lower gene expressions of placental <i>HO-1</i>, <i>GPX2</i>, <i>IL-8</i>, and <i>IL-6</i> were found in the VD₃ or 25-OH-D₃ groups (<i>p</i> < 0.05 or <i>p</i> < 0.10), while higher gene expressions of <i>GLUT1</i> and <i>SNAT2</i> in the placenta of sows were observed in the VD₃ and 25-OH-D₃ groups, respectively (<i>p</i> < 0.05). These findings indicate that the supplementation of VD₃ and 25-OH-D₃ in the diet of sows can improve their plasma oxidative stress status, enhance placental antioxidant capacity and nutrient transport, and reduce placental inflammatory responses, with more pronounced improvements in sow performance observed in sows fed diets supplemented with 25-OH-D₃.