The Effects of Vitamin D3 Supplementation in Late Gestation on Lactation Performance, Constipation and Intestinal Microbiota of Sows

This study was conducted to systematically evaluate the effects of dietary vitamin D3 supplementation during late gestation on constipation, gut microbiota, and lactation performance in sows. A total of 42 healthy sows with similar parity and gestational status were randomly assigned to two groups on gestation day 75 (G 75): CON (basal diet), VD3 (2340 IU/kg was supplemented daily from G 75 to G 90). Analysis of constipation-related indicators showed that the incidence of constipation before (p < 0.05) and after farrowing (p < 0.01) was significantly lower in the vitamin D3 supplementation group, and constipation cases in this group were predominantly classified as mild (p < 0.05). In addition, fecal moisture content was significantly higher in the vitamin D3 supplementation group on G 109 (p < 0.05). Inflammation-related marker analysis showed that, compared with the CON group, sows in the VD3 group had significantly lower fecal calprotectin concentrations on G 109 (p < 0.05). Further Spearman correlation analysis showed that fecal calprotectin concentration was significantly negatively correlated with piglet weaning survival rate (p < 0.01). Gut microbiota analysis showed that vitamin D3 supplementation significantly increased the relative abundance of Clostridium and altered gut microbial composition and predicted KEGG functional profiles in sows. Although the difference did not reach statistical significance, piglets in the VD3 group showed a tendency toward a higher weaning survival rate (p = 0.08). Overall, these findings indicate that late-gestation dietary vitamin D3 supplementation was associated with a lower incidence of peripartum constipation and alterations in gut microbial community composition and predicted functional profiles in sows. Its potential effects on piglet weaning outcomes require further investigation in studies with larger sample sizes.