Effects of Raffinose on Growth Performance, Intestinal Function-Related Genes, and Cecal Microbiota in Broilers Fed Low Soybean Meal Diets

This study investigated the effects of a low soybean meal (SBM) diet and its supplementation with graded levels of raffinose on the growth performance, expression of genes related to nutrient transport and intestinal function, and cecal microbiota of white-feathered broilers. A total of 480 one-day-old Cobb broilers were randomly allotted to six isoenergetic and isonitrogenous dietary treatments, each with eight replicates of 10 birds. The diets consisted of a positive diet, a low SBM diet (10% reduction in SBM), and the low SBM diet supplemented with 0.10%, 0.15%, 0.20%, or 0.25% raffinose. Results indicated that, compared with the positive diet, the low SBM diet significantly increased (p < 0.05) the overall mortality and average daily feed intake (ADFI) during days 22–42, while significantly decreasing (p < 0.05) dietary ether extract (EE) availability. Raffinose supplementation to the low SBM diet linearly reduced (p < 0.05) dietary gross energy and dry matter utilization and downregulated duodenal SLC5A1 gene expression at 42 days, while linearly increasing (p < 0.05) the cecal isobutyric acid content. A decreasing tendency in mortality during days 22–42 was also observed with raffinose inclusion (p = 0.088). Notably, the low SBM diet elevated the relative abundance of Campylobacterota and Helicobacter, which was effectively reversed by raffinose supplementation. In conclusion, a 10% reduction in dietary SBM negatively affected the survival, nutrient utilization, and cecal microbial structure in broilers, whereas raffinose supplementation partially modulated these alterations.