Dietary effect of substituting Saccharina japonica with cabbage extract by‐product on the growth, body composition and air exposure of juvenile abalone (Haliotis discus hannai Ino 1952)

Abstract

Dietary substitution effect of cabbage extract by‐product (CEB) for Saccharina japonica on the growth, body composition and air exposure stressor of juvenile abalone (Haliotis discus hannai) was determined. A total of 1260 abalone were randomly distributed into 18 net cages (seventy per cage). Five formulated diets were prepared. The control (CEB0) diet contained 20% S. japonica powder. Twenty-five, 50%, 75%, and 100% of S. japonica were substituted with the equal amount of CEB, referred to as the CEB25, CEB50, CEB75 and CEB100 diets, respectively. Ultimately, dry S. japonica was prepared to compare formulated diets on growth of abalone. Each diet was randomly assigned to triplicate groups of abalone and fed to abalone every other day for 16 weeks. After the 16-week feeding trial, abalone were subjected to air exposure for 24 h, and then survival was monitored for the next 6 days. All formulated diets achieved 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 dietary increased substitution levels of S. japonica with CEB. Shell growth of abalone tended to agree with growth rate. The chemical composition of the soft body of abalone was not affected by the experimental diets. Survival of abalone fed all formulated diets was (P < 0.05) higher than that of abalone fed S. japonica at the end of the 6-day post observation period after the 24-h air exposure. In conclusion, S. japonica could be completely (100%) substituted with CEB in abalone feeds when 20% S. japonica was included. Substitution of S. japonica with CEB in feeds could improve growth of abalone, but lower feed cost.