Comparison of broccoli by-product meal and ethoxyquin as feed additives in abalone (Haliotis discus, Reeve 1846) diets: Impacts on survival, growth, and resistance to stressor conditions

Inclusion of an additive in diets can enhance nutritional adequacy, support growth, and improve survival in aquaculture species. Broccoli by-product meal (BBM) is rich in various nutrients and bioactive compounds. We compared the effects of BBM and commercial antioxidant, ethoxyquin, as feed additives in diets on survival, growth, and resistance to various stressor conditions in abalone ( Haliotis discus ). Seven isoproteic and isolipidic diets were formulated containing 0, 0.5, 1, 2, 3, and 5% BBM, as well as a diet with 0.001% ethoxyquin, designated as the Con, BBM 0.5 , BBM 1 , BBM 2 , BBM 3 , BBM 5 , and Ethoxyquin diets, respectively. Dried Saccharina japonica was also prepared to assess the impacts of these diets on abalone. A total of 2880 juveniles were randomly allocated into 24 net cages (120 abalone per cage) in triplicate. Abalone were fed the experimental diets once daily for 16 weeks. Following the 16-week feeding period, 60 abalone were randomly obtained from each net cage to conduct stress-resistance tests (the 20-h air exposure, 20-h high temperature at 30°C, and 12-h low salinity at 25 g/L). Statistically ( P < 0.014) higher survival was obtained in abalone fed the BBM 3 and BBM 5 diets compared to those fed the S. japonica . Increasing dietary inclusion levels of BBM led to a linear improvement in abalone survival. All formulated diets, except for the Ethoxyquin diet, led to greater weight gain and weight-specific growth rate of abalone than the S. japonica . Principal component analysis based on performance variables showed that the first two principal components accounted for 77% of the total variation (PC1: 61.2% and PC2: 15.8%), with survival contributing most strongly to PC1. However, the proximate composition of the soft body of abalone, except for ash content, were not significantly changed by dietary treatments. Dietary supplementation of BBM did not cause any negative impact on survival of abalone across all stressor tests. In conclusion, inclusion of BBM in diets linearly improved the survival of abalone, with 5% BBM having the greatest improvement effect in the 16-week feeding trial. • Broccoli by-product meal was developed as a safe and cost-effective feed additive in diets for abalone culture. • Higher survival was obtained in abalone fed the BBM 3 and BBM 5 diets compared to those fed the S. japonica . • Dietary inclusion of BBM linearly improved survival of abalone, with 5% BBM having the greatest improvement effect.