Effects of fiber concentrations and fermentation rates on reproductive performance, nutrient digestibility, immune response, and microbiota of lactating sows.

Certain types of fiber inclusion in sow diets can offer benefits such as promoting a healthy microbiome, improving intestinal health, and enhancing welfare through satiety mechanisms. While most research has focused on gestating sows, studies on lactating sows, especially regarding fiber types, levels, and fermentation rates, are limited. This study explored how fiber inclusion and fermentation rate affect lactation performance, nutrient digestibility, immune response, and microbiota. The study involved 136 lactating sows (Landrace × Large White) assigned to four dietary treatments with varying total dietary fiber (TDF) levels and proportions of fast-fermentable fiber. Diets 1 and 2 had low TDF (15%), while Diets 3 and 4 had high TDF (25%). Fast-fermentable fiber was included at 1.25% and 2.5% in the low-fiber diets, and at 3.75% and 5% in the high-fiber diets. Fiber sources like sugar beet pulp, oat hulls, wheat millrun, and barley were used based on their fermentable fiber proportions, measured using an in-house Trouw Nutrition assay. Effective energy, crude protein (CP), and lysine contents were consistent across diets. Sows were fed starting at 3 kg/d (primiparous) or 3.5 kg/d (multiparous), increasing to 7 kg/d or 8 kg/d by 8 or 9 d postfarrowing. High-fiber diets reduced apparent total tract digestibility (ATTD) of nutrients (P < 0.001) but increased sow fat loss (P < 0.05). Sows consuming fast-fermentable fiber had lower body weight (BW) and protein loss (P < 0.05), decreased serum interleukin-8 (IL-8) levels (P < 0.05), and improved ATTD of gross energy (P = 0.016), dry matter on day 19 (P < 0.001), CP (P < 0.001), and nitrogen (P < 0.001) and a trend toward higher fat levels in milk (P = 0.099). High-fiber diets decreased microbiota diversity but increased beneficial families such as Prevotellaceae, Ruminococcaceae, and Lachnospiraceae. Although high-fiber diets lowered ATTD of nutrients, feeding these diets during lactation improved sow performance without negatively affecting feed intake, milk composition, microbiota and did not impact litter weaning weight. Fast-fermentable fiber also reduced IL-8 levels, BW loss, and protein loss, suggesting it benefits lactating sows.