Alterations in intestinal development and barrier function in response to dietary β-mannanase in growing broilers

This study evaluated the effects of dietary β-mannanase supplementation on growth performance, intestinal development, nutrient digestibility, and cecal microbiota in growing broilers. A total of 160 chicks were assigned to one of two dietary treatments (8 replicates of 10 birds each) and were fed a basal corn-soybean meal diet (Ctrl) or a basal diet supplemented with 150 mg/kg β-mannanase until day 21. With similar body weight, β-mannanase supplementation significantly reduced feed intake and improved the feed conversion ratio from day 1 to 21 (p < 0.05). Compared with the Ctrl group, β-mannanase supplementation reduced chyme viscosity and upregulated jejunal mRNA expression of sodium-dependent glucose cotransporter 1 (SGLT1) and fatty acid-binding protein 6 (FABP6) (p < 0.05). Although the addition of β-mannanase to the diet did not affect the length and weight of the duodenum and jejunum, it notably increased the villus height-to-crypt depth ratio in the jejunum (p < 0.05), as well as the DNA content, a quantitative parameter of enterocytes, in both the duodenum and jejunum, contributing to a significant increase in the digestibility of dry matter and metabolizable energy. Regarding barrier integrity, β-mannanase supplementation decreased serum D-lactic acid and endotoxin levels and upregulated jejunal expression of zonula occludens-1 (ZO-1), occludin, and mucin-2 at day 21 (p < 0.05). Furthermore, β-mannanase supplementation significantly increased the levels of secretory immunoglobulin A (sIgA) and reduced the expression of interleukin-1 beta (IL-1β) in the jejunum. Cecal microbiota analysis revealed that β-mannanase increased the relative abundance of g_Alistipes_A_871400, g_Lachnoclostridium_A_130679, g_Enterocloster, and g_Comamonas_F_58925. These findings indicate that dietary β-mannanase improves gut micro-ecology by reducing chyme viscosity, enhancing intestinal barrier function, and modulating microbiota composition, thereby promoting nutrient utilization and feed efficiency in growing broilers.