Dietary substitution effect of Saccharina japonica with residues of citrus juice production in formulated diets on the growth, body composition and air exposure of juvenile abalone (Haliotis discus, Reeve 1846)

Abstract

Dietary substitution effect of Saccharina japonica with residues of citrus juice production (RCJP) on the growth and body composition of abalone (Haliotis discus) subjected to air exposure was determined. A total of 1260 abalone were randomly distributed into 18 net cages (seventy per cage). Five formulated diets were prepared. The control (RCJP0) diet included 20% S. japonica. The percentages of 25, 50, 75 and 100 of S. japonica were substituted with the same amount of RCJP, referred to as the RCJP25, RCJP50, RCJP75 and RCJP100 diets, respectively. Finally, dry S. japonica was prepared to evaluate the formulated diets on growth performance of abalone. Each diet was randomly assigned to triplicate groups of abalone. Abalone were daily fed to satiety with little leftover for 16 weeks. After the 16-week feeding trial, abalone were subjected to air exposure stressor for 20 h, and then survival was monitored for the next 120 h. All formulated diets achieved significantly greater weight gain and specific growth rate (SGR) than those of abalone fed the S. japonica. Weight gain and SGR of abalone linearly improved with an increased substitution levels of S. japonica with RCJP in feeds. The greatest weight gain and SGR were obtained in abalone fed the RCJP100 diet. The shell growth and soft body weight of abalone also linearly increased with dietary substitution levels of S. japonica with RCJP. The chemical composition of the soft body of abalone was not affected by the experimental diets. Survival of abalone fed all formulated diets, except for the RCJP0 diet was significantly higher than that of abalone fed the S. japonica at the end of the 120-h post observation. In conclusion, S. japonica could be entirely (100%) replaced with RCJP in formulated abalone diet. The greatest growth performance was obtained in abalone fed the RCJP100 diet.