Growth performance, nutrient digestibility, antioxidant status and metabolic enzyme activity in pearlspot (Etroplus suratensis), fed carbohydrates of different complexities

Carbohydrate utilization by fish is influenced by many factors and structural complexity is one among them. A 60-days feeding study was conducted to assess the capacity of pearlspot, Etroplus suratensis to utilize different complexity of carbohydrate in growth performance, nutrient digestibility, antioxidant status, metabolic and digestive enzyme activity and histology of liver. Five isonitrogenous (35%) and isolipidic (7%) diets were formulated to contain 35% of glucose (GLU-feed), sucrose (SUC-feed), dextrin (DEX-feed), starch (STA-feed) and cellulose (CEL-feed), respectively. The survival and condition factor were not affected (p > 0.05) by the diets. Fish fed with the STA-feed showed significantly (p < 0.05) higher weight gain and specific growth rate. The feed efficiency ratio and protein efficiency ratio were significantly higher (p < 0.05) and alike in STA-feed and Dex-feed groups. Except for protein, the other whole-body composition was affected significantly (p < 0.05) by the different carbohydrate sources. The activities of antioxidant enzymes were significantly (p < 0.05) higher in groups fed on complex carbohydrate diets. Simillar trend was observed in the protease enzyme activity. Significantly (p < 0.05) higher dry matter digestibility was recorded in starch fed group. STA-feed group increased the specific activity of malate dehydrogenase and hexokinase.The glucose 6 phosphate dehydrogenase (G6PDH) activity was significantly (p < 0.05) higher in the GLU-feed group, and gradually decreased with increase in the complexity of carbohydrates.The DEX-feed and CEL-feed groups showed heavy fatty change with numerous large lipid droplets as compared to other groups. Overall, these results indicate that dietary starch was more efficiently utilized than other carbohydrate sources by pearlspot.