Modulation of intestinal morphology and microbial ecosystem by Bacillus-based biotics and enzyme cocktails in...

This study investigated the effects of Bacillus-based biotics and enzyme cocktails on growth performance, physiological homeostasis, and the intestinal ecosystem in broilers fed a standardized dietary matrix. A total of 105 one-day-old male broilers were assigned to five dietary treatments: (1) CON (basal diet), (2) A (0.05% probiotics), (3) B (0.1% one-strain synbiotics), (4) C (0.1% two-strain synbiotics), and (5) D (0.1% enzyme cocktail). No significant differences were observed in body weight or average daily gain across treatments, although phase-specific differences in average daily feed intake were detected (p < 0.05). Serum biochemical parameters and total bile acid concentrations remained stable, indicating physiological homeostasis. In the fermentation microenvironment, ileal butyrate concentrations tended to increase in Treatment C compared with CON (p = 0.10). In addition, Treatment C significantly increased the duodenal villus height-to-crypt depth ratio (p < 0.05). Most notably, beta-diversity analysis using Jaccard distance and Bray-Curtis dissimilarity revealed a significant reconfiguration of the cecal microbial community (p < 0.05), with Treatments C and D exhibiting the most distinct clustering patterns. Although dietary biotics and enzyme cocktails altered intestinal morphology and microbial beta-diversity, and showed limited modulation of the fermentation microenvironment, these shifts did not translate into systemic growth enhancement.