Star anise extract supplementation improved growth performance, hepatic-antioxidant enzyme status, hematology, serum biochemistry, and survival against crowding stress in Catla catla

This study was conducted to evaluate the effectiveness of star anise extract (SAE) (prepared using ethanol as the solvent) on growth, proximate composition, hepatic-antioxidant enzyme status, blood-serum indices, and survival against crowding stress in Catla calta. Healthy fingerlings (N = 900) with an average initial weight of 14.16 ± 0.11 g were acclimatized under laboratory conditions and then placed in 5 hapas (60 fish in each) in triplicate. SAE was supplemented in basal feed at 0.0, 0.5, 1.0, 2.0 and 4.0 g/kg and fed to the experimental groups up to satiation twice daily for 90 days. After completion of the feeding trial, 40 fish from each treatment were subjected to crowding stress (60 kg/m3) in triplicate. In the feeding trial, orthogonal polynomial contrast analysis revealed significant enhancement in final weight, weight gain and specific growth in linear and quadratic trends with weight gain percentage, feed conversion ratio and protein efficiency in a quadratic trend observed in response to SAE supplementation. The optimum supplementation level of SAE based on weight gain % was estimated to be 0.93 g/kg using broken line regression analysis (R2 = 0.97) for C. catla. No significant differences in survival rate or proximate composition were observed during the feeding trial. Dietary supplementation with SAE improved the activities of antioxidant enzymes (catalase, superoxide dismutase and glutathione peroxidase) in linear and quadratic trends. The activities of hepatic enzymes, such as alanine transferase, alkaline phosphatase and aspartate transaminase, were also enhanced linearly and quadratically in response to SAE supplementation. Furthermore, hematological indices (red blood cells, white blood cells, hematocrit, hemoglobin and mean corpuscular hemoglobin concentration) were also significantly improved with SAE supplementation. The serum total protein, albumin and globulin concentrations increased linearly and quadratically. Furthermore, stress markers (glucose, cortisol) and triglycerides were significantly reduced linearly and quadratically in response to SAE supplementation. Lysozyme activities also increased linearly and quadratically, indicating a better immune response. After 7 days of crowding stress, the lowest cumulative mortality was observed for the fish fed a diet supplemented with 1.0 g/kg SAE. In conclusion, dietary SAE supplementation significantly improved growth, hepatic-antioxidant enzyme status, blood-serum indices and survival against crowding stress in C. calta.