Effects of dietary acorn supplementation on growth performance, nutrient digestibility and gut microbial metabolism in finishing pigs

Abstract Background The sustainable utilization of alternative feed resources is increasingly important for improving nutrient efficiency and promoting intestinal health in pig production. Acorns are abundant plant-derived resources containing carbohydrates, dietary fiber, and bioactive compounds; however, their potential as a functional feed ingredient for finishing pigs remains insufficiently characterized. This study aimed to investigate the effects of dietary acorn supplementation on growth performance, nutrient digestibility, gut microbiota composition, and short-chain fatty acid (SCFA) production in finishing pigs. Results Ninety Yuxi pigs were randomly allocated to five dietary treatments supplemented with 0, 200, 300, 400, or 500 g/kg acorn for 120 days. Dietary supplementation with 200 g/kg acorn significantly increased average daily gain and improved feed conversion ratio, whereas excessive acorn inclusion (400 and 500 g/kg) negatively affected growth performance. Acorn supplementation improved the apparent digestibility of calcium, neutral detergent fiber, and acid detergent fiber, while high-level acorn inclusion reduced crude protein digestibility, potentially due to increased tannin content. Microbial analysis based on 16S rRNA sequencing demonstrated that acorn supplementation increased bacterial richness and modulated intestinal microbial composition. Specifically, moderate acorn supplementation promoted the enrichment of fiber-associated and fermentation-related microbial taxa, including Bifidobacterium , Roseburia , Oscillospira , Treponema , and Prevotella . PICRUSt2-based functional prediction further indicated that acorn supplementation altered microbial metabolic potential, particularly pathways involved in carbohydrate degradation, central fermentation, and energy metabolism. Consistently, colonic butyrate concentrations were significantly increased in pigs receiving 200 and 300 g/kg acorn diets, suggesting enhanced microbial fermentation capacity and improved intestinal metabolic function. Conclusions Moderate dietary acorn supplementation, particularly at 200 g/kg, improves growth performance, nutrient utilization, and intestinal microbial homeostasis in finishing pigs. These beneficial effects are associated with the enrichment of fiber-degrading and SCFA-producing microbiota and increased butyrate production. The findings suggest that acorns have potential as a sustainable alternative feed ingredient for improving pig production efficiency and gut health.