Combined effects of dietary ellagic acid and Bacillus coagulans on growth performance, antioxidant and immune responses, intestinal health, and resistance to Streptococcus agalactiae in striped catfish.

This study evaluated the individual and combined effects of dietary ellagic acid (EA) and Bacillus coagulans (BC) on growth performance, physiological status, intestinal health, and resistance to Streptococcus agalactiae in striped catfish (Pangasianodon hypophthalmus). Juvenile fish were assigned to four dietary treatments for 60 days, with four replicate hapas per treatment: a basal diet (control), EA at 100 mg kg⁻¹ diet, BC at 2.0 g kg⁻¹ diet (nominally 5.0 × 10⁶ colony-forming units [CFU] g⁻¹ diet), or the combined EA + BC diet. Dietary EA and/or BC improved growth and feed utilization, increased intestinal amylase, lipase, and protease activities, and favorably altered whole-body composition, with the greatest overall responses generally recorded in the EA + BC group (P < 0.05). Supplemented fish also showed higher erythrocyte, hemoglobin, and leukocyte values; increased serum protein fractions; enhanced hepatic antioxidant enzyme activities; and higher lysozyme activity, total circulating immunoglobulin M (IgM), and phagocytic responses. Serum aminotransferase activities, uric acid, total cholesterol, and hepatic malondialdehyde were reduced. Culture-based analyses showed higher presumptive counts of lactic acid bacteria and lower total culturable aerobic bacterial counts. Antioxidant-related transcripts (SOD, CAT, and GPx) were upregulated in the liver, whereas splenic TLR1 was upregulated and TNF-α and IL-1β were downregulated. Following the S. agalactiae challenge, descriptive cumulative mortality was about 87%, 31%, 21%, and 12% in the control, EA, BC, and EA + BC groups, respectively. Two-way ANOVA demonstrated substantial main effects of both additives and significant EA × BC interactions for selected indices. Generally, the combined diet produced the most consistent improvements across growth, physiological, intestinal, antioxidant, immune, and disease-resistance indicators.