Effects of Dietary Ratio of Insoluble Fiber to Soluble Fiber on Reproductive Performance, Biochemical Parameters, and Fecal Microbial Composition of Gestating Sows

This study aimed to investigate the effects of dietary ISF:SF ratio on reproductive performance, biochemical parameters, colostrum composition, and fecal microbial composition in gestating sows. A total of 30 multiparous sows were randomly allocated to three dietary treatment groups: 8% inulin diet (ISF:SF 1.14, Inulin group), 8% cotton fiber diet (ISF:SF 6.61, Cotton group), and 4% inulin + 4% cotton fiber diet (ISF:SF 2.37, Inulin + Cotton group). The results showed that, compared to the other groups, the Inulin group had a significantly higher number of piglets born alive, as well as increased plasma concentrations of acetic acid, butyric acid, hexanoic acid, and total short-chain fatty acids (SCFAs) (<i>p</i> < 0.05). Sows in the Inulin group had significantly lower fecal scores than those in the other groups from days 81 to 85 and from days 106 to 110 of gestation (<i>p</i> < 0.05). On day 90 of gestation, the serum levels of albumin, urea, uric acid, calcium, and phosphorus in the Inulin group were significantly lower than those in the other groups (<i>p</i> < 0.05). Additionally, the serum levels of triacylglycerol in the Inulin + Cotton Fiber group were significantly higher than those in the other groups (<i>p</i> < 0.05). However, there were no significant differences in serum concentrations of total protein, creatinine, glucose, cholesterol, HDL-cholesterol, or LDL-cholesterol among the treatments (<i>p</i> > 0.05). On day 110 of gestation, the serum content of urea, uric acid, calcium, and phosphorus in the Inulin group was significantly lower than those in the other groups (<i>p</i> < 0.05). Furthermore, the plasma levels of uric acid, triacylglycerol, and HDL-cholesterol in the Inulin + Cotton Fiber group were significantly higher than those in the Cotton Fiber group (<i>p</i> < 0.05), while the creatinine levels in the Inulin group were higher than those in the other groups (<i>p</i> < 0.05). No differences were observed in the composition and immune performance of colostrum (<i>p</i> > 0.05). Microbial sequencing analysis showed that dietary inulin supplementation to increase the proportion of soluble fiber significantly decreased the abundance of Firmicutes, Clostridia, Clostridiales, Lachnospiraceae, Streptococcaceae, and <i>Streptococcus</i> (<i>p</i> < 0.05). The abundance of short-chain fatty acid-producing microorganisms—Bacteroidetes, Bacteroidia, Bacteroidales, and Muribaculaceae—was significantly increased (<i>p</i> < 0.05). The results indicated that inulin supplementation decreased the dietary ISF:SF ratio, significantly alleviated constipation in sows, increased the number of piglets born alive, regulated intestinal microecology, and increased the plasma concentrations of short-chain fatty acids (SCFAs), including acetic, propionic, and butyric acids.