Dietary Supplementation with Protocatechuic Acid and a Complex Eucommia ulmoides Leaf Extract Differentially Enhanced...

Nutrition during late pregnancy plays a critical role in fetal development. This study was conducted to investigate the effects and underlying mechanisms of protocatechuic acid (PCA) and PCA-rich Eucommia ulmoides leaf extract (EU) on reproductive performance using late-pregnancy sows as a model. A total of 30 sows (Landrace × Yorkshire; average parity: 3-4) with similar body condition (assessed as a score of 4 on a 5-point scale) were randomly assigned to three treatments (n = 10 per group) from day 80 of gestation until farrowing and fed either a basal diet, a basal diet supplemented with 200 g/t of PCA, or 1000 g/t of EU. Results demonstrated that dietary supplementation with PCA and EU, which delivered a negligible amount of PCA but contained other bioactive phytochemicals such as chlorogenic acid, significantly increased litter weight at birth and the number of healthy piglets (p < 0.05), along with elevated levels of colostral immunoglobulins and reduced serum interleukin (IL)-6 concentrations (p < 0.05). Furthermore, PCA supplementation was associated with a decrease in fasting glucose levels and improved insulin sensitivity (p < 0.05), accompanied by an increased relative abundance of Bacteroidetes (p < 0.05). Analysis of gut microbial composition revealed that both PCA and EU reduced the relative abundance of Paraprevotella (p < 0.05), while PCA increased the abundance of the dgA11_gut_group (p < 0.05), and EU enriched Caldicoprobacter (p < 0.05). Correlation analysis indicated that PCA- and EU-modulated genera, such as Lysinibacillus, were positively associated with colostrum lactose and colostrum fat but negatively correlated with the number of somatic cells, colostrum protein, degreased dry matter, total solids, and urea nitrogen (p < 0.05). In conclusion, dietary supplementation with PCA and EU differentially enhanced reproductive performance and colostrum immunoglobulins, at least partially, through the modulation of inflammation and glucose metabolism-related gut microbiota in late-pregnancy sows.