Corn-starch based formulated diet has growth and feed utilization efficiency advantages over trash fish diet for juvenile golden pompano Trachinotus ovatus

Until now, trash fish/low valued fish continues to be widely used in marine cage culture of pompano and many other carnivorous species in China and other Asian countries. This study is the first attempt to compare the performance of juvenile golden pompano Trachinotus ovatus fed trash fish or starch-based formulated diets. Three isonitrogenous (41 %) and isolipidic (11 %) diets containing 16, 22 or 28 % corn starch were prepared. Juvenile pompano (mean initial weight: 28.0 ± 0.3 g) were fed either formulated diets or trash fish on a equivalent dry-matter basis for 8 weeks. The survival rates were significantly higher in fish fed starch diets than fish fed trash fish (P < 0.05). Specific growth rate (SGR) of fish fed the 22 % and 28 % starch diets was significantly higher than fish fed 16 % starch diet and trash fish. Feed intake (FI) of fish fed trash fish was significantly higher than those fed formulated diets; however, feed efficiency (FE) and protein efficiency ratio (PER) of fish fed the formulated diets were higher than those fed trash fish, with the 22 % starch dietary group having a significantly higher FE value than fish fed trash fish. The whole-body energy retention (ER) of fish fed the diet containing 22 % starch had the highest ER, significantly higher than those fed 16 % starch and trash fish. The moisture in whole-body tissues of fish fed trash fish was significantly higher than the formulated dietary groups. On the other hand, whole-body protein and lipid contents of fish fed the 22 % starch diet was significantly higher than the other dietary treatments. The whole-body lipid level of fish fed trash fish was significantly lower than the other dietary groups. The body condition indices were significantly higher for fish fed formulated diets compared to those fed trash fish. The viscerosomatic index (VSI) was decreased with increasing dietary starch levels. Hexokinase (HK) activity significantly increased with increasing dietary starch levels, whereas pyruvate kinase (PK) activity had an opposite trend. The liver and muscle glycogen contents were generally increased with increasing dietary starch levels. In addition, the intestinal microbial communities of fish fed the formulated diets and trash fish was distinctly different. The results shown that formulated diet had advantages in performance and feed utilization efficiency over trash fish. Corn starch can be used as a suitable dietary carbohydrate. Evaluated on growth and FE, the optimal dietary corn starch level for T. ovatus is 22–24 % of diet.