Effect of dietary supplementation of Cladophora glomerata meal on growth, physiological indices, and expression of genes related growth and immunity in ornamental goldfish (Carassius auratus)

A 10-week feeding trial was conducted to investigate the effects of dietary supplementation of Cladophora glomerata (CG) powder on growth, feed utilization, carcass composition, hematology, and expression of genes related to growth and immunity in ornamental goldfish ( Carassius auratus ) . Five isonitrogenous and isolipidic diets containing 0 (control), 25, 50, 75, and 100 g/kg of CG (CG25 - CG100) were fed to triplicate groups of 20 fish (initial body weight: 5.02 ± 0.00 g) to apparent satiation for 10 weeks. At the end of the trial, dietary CG supplementation linearly improved growth and protein efficiency, with a quadratic increase in protein productive value. Crude protein and fat increased both linearly and quadratically, with CG100 showing the highest levels. The a* and b* values increased linearly in all organs, with b* in the head and tail showing a quadratic response. Furthermore, CG at 50 -100 g/kg significantly increased total carotenoids content in fins, liver, and serum, while 75–100 g/kg increased the levels in muscle and skin. White blood cell count, red blood cell count, and hematocrit levels increased linearly and quadratically, while hemoglobin increased linearly. Conversely, AST, triglycerides, and LDL-c cholesterol decreased versus the control group. Supplementation of CG higher than 50 g/kg exhibited a linear increase in the liver growth-related genes (IGF-1, IGF-2) and linear and quadratic increase in the expression of anti-inflammatory (IL-10) and pro-inflammatory (TNF-α, IL-1α) cytokine genes in goldfish. The hepatocyte histomorphology of goldfish fed diets supplemented with CG exhibited no significant differences compared to the control group. In conclusion, supplementation of diets with 50–100 g/kg CG markedly enhanced growth performance and increased a * pigmentation values in the head, abdomen, and tail regions. This inclusion level also elevated total carotenoid concentrations in the fins, muscle, and serum, and induced the upregulation of genes related to growth (IGF-1, IGF-2) and immune response (TNF-α, IL-1α, IL-10), along with lysozyme mRNA expression. These findings suggest that C. glomerata supplementation at 50–100 g/kg could contribute to enhanced growth and modulation of pigmentation and immune-related responses in goldfish. • Cladophora glomerata (CG) meal improved growth and feed utilization with reduced FCR. • Supplementing CG at 50 g/kg significantly enhanced head, abdominal, and tail coloration. • CG supplementation above 50 g/kg upregulated immune and growth-related genes expression.