Dietary inclusion effect of citrus peel by-product as an additive on the growth performance, body composition, and various stress resistance of juvenile abalone (Haliotis discus) compared to ethoxyquin

Abstract

Dietary additive can effectively improve growth performance and stressor resistance of aquatic animals. Dietary inclusion effect of citrus peel by‐product (CPB) as an additive on the growth, body composition, and various stress resistance of juvenile abalone (Haliotis discus) was investigated, and compared to commercial antioxidant (ethoxyquin). A total of 2880 juvenile (initial weight of 3.3 g) abalone were randomly assigned into 24 net cages. Seven formulated diets supplemented with 0, 5, 10, 20, 30, and 50 g/kg CPB and 0.01 g/kg ethoxyquin were formulated, and referred to as the CPB0, CPB5, CPB10, CPB20, CPB30, CPB50, and EQ diets, respectively. Finally, dry Saccharina japonica was prepared to compare the formulated diets on growth of abalone. All experimental diets were assigned to triplicate groups of abalone. Abalone were daily fed to satiation for 16 weeks. After the 16-week feeding trial, sixty abalone from each cage were subjected to the 20-h air, 12-h low salinity at 25 psu, and 20-h high temperature at 30 °C exposure stressors, respectively, and then survival was monitored. Abalone fed all formulated diets produced superior weight gain, specific growth rate (SGR), shell growth to abalone fed the S. japonica. Dietary inclusion levels of CPB linearly improved weight gain of abalone. However, there was no difference in chemical composition of the soft body of abalone fed all experimental diets. Diets supplemented with CPB or EQ improved survival of abalone when subjected to the 20-h air and high temperature exposures. In conclusion, CPB was a very effective additive as growth enhancer as well as stress reducer in abalone diet. Abalone fed the CPB50 diet attained the highest weight gain, SGR, and stress resistance subjected to the 20-h air and high temperature exposures.