Histological Assessment of Hepatic and Intestinal Responses in Cyprinus carpio Fed with Bacillus coagulans: A 60-Day Dose-Dependent Study.

Abstract

Probiotics are increasingly utilized in aquaculture to enhance fish health, yet their tissue-level effects remain underexplored in freshwater species. This study investigated the dose- and time-dependent effects of dietary Bacillus coagulans on liver and intestinal histology in Cyprinus carpio over a 60-day feeding trial. A total of 180 fingerlings were divided into four groups: control (basal diet) and three treatment groups receiving 0.05 × 10⁹, 0.1 × 10⁹, or 0.15 × 10⁹ CFU g⁻¹ of B. coagulans. Liver and intestinal tissues were sampled at 20, 40, and 60 days, fixed in formalin, processed, and examined using hematoxylin and eosin staining. Histological analysis revealed progressive, dose-dependent improvements in hepatocyte integrity, lobular organization, and sinusoidal structure, with T3 (highest dose) showing near-normal hepatic architecture by day 60. Similarly, intestinal morphology improved with increased villus height, goblet cell density, and epithelial continuity, particularly in higher-dose groups, indicating enhanced mucosal barrier function and absorptive capacity. No signs of necrosis, inflammation, or tissue degeneration were observed in probiotic-fed fish, confirming safety and biocompatibility. These findings align with previous reports on probiotics enhancing metabolic efficiency, mucosal immunity, and tissue health in freshwater fish. Overall, dietary supplementation with B. coagulans at 10⁹ CFU g⁻¹ over 60 days effectively promotes liver and intestinal health in common carp, supporting its application as a functional feed additive in sustainable aquaculture.