Effect of seven carbohydrate sources on juvenile Penaeus monodon growth performance, nutrient utilization efficiency and hepatopancreas enzyme activities of 6-phosphogluconate dehydrogenase, hexokinase and amylase

Seven isoproteic (370 g/kg) and isolipidic (90 g/kg) diets containing seven various carbohydrate sources (wheat starch, sucrose, potato starch, maize starch, dextrin, maltose and glucose) at the same quantities (200 g/kg) were fed to triplicate groups of Penaeus monodon (1.92 ± 0.01 g mean initial wet weight) for 74 days. All shrimp fed glucose and maltose-containing diets died within the first two weeks. After a 74-day feeding trial, the highest (P<0.05) weight gain (WG, %) and biomass gain (BG, g) were obtained with shrimp fed wheat starch or sucrose-containing diet; whereas, the lowest (P<0.05) WG and BG were observed for shrimp fed a dextrin-containing diet. The survival of shrimp fed wheat starch, sucrose, potato starch and maize starch-containing diets was higher (P<0.05) than shrimp fed a dextrin-containing diet, but no difference (P>0.05) was found among shrimp fed wheat starch, sucrose, potato starch and maize starch-containing diets. The highest and lowest protein contents of whole body and muscle were obtained from shrimp fed wheat starch and dextrin-containing diets, respectively. Diets containing dextrin or maize starch had inferior values of apparent digestibility coefficients (ADCs) of protein, dry matter and energy (P<0.05) compared to the three other diets, while dextrin or potato starch-containing diet gave the worst response in terms of ADC of carbohydrate (P<0.05). The highest 6-phosphogluconate dehydrogenase (6PGDH) and hexokinase (HK) activities were observed in shrimp fed a wheat starch-containing diet. Hepatopancreas amylase activity of shrimp fed a wheat starch and sucrose-containing diet was higher (P<0.05) than that of shrimp fed other diets. In conclusion, shrimp fed the wheat starch or sucrose-containing diet had the best growth performance. The activities of hepatopancreas enzymes involved in carbohydrate uptake (HK) and NADPH generation (6PGDH) increased preferentially as dietary carbohydrates became more suitable to support the shrimp's rapid growth. All these data suggest that wheat starch and sucrose are the more suitable source of dietary carbohydrate and have the same nutritional value in P. monodon feed.