# Dietary Supplementation Impact of Combined Broccoli and Citrus Peel By‐Products on the Growth Performance of Japanese Abalone (Haliotis discus, Reeve 1846) and Stress Resistance to Various Stressors

## TL;DR

Adding broccoli and citrus peel by-products to abalone diets improves their growth and helps them survive stressful conditions like high temperatures and air exposure.

## Contribution

This study demonstrates that combining broccoli and citrus peel by-products in abalone feed enhances stress resistance and growth performance.

## Key findings

- Abalone fed with CBC showed higher growth rates and better physical measurements compared to those fed with S. japonica.
- CBC inclusion of at least 2% improved survival rates under air exposure and high temperature stress.
- CBC2, CBC3, and CBC5 diets significantly outperformed S. japonica in stress resistance tests.

## Abstract

This experiment was conducted to investigate the impacts of dietary incorporation of a combination of broccoli by‐product and citrus peel by‐product (CBC) as a functional additive on the growth and resistance of the Japanese abalone (Haliotis discus) under various stressor conditions. A total of 2520 abalone juveniles (initial weight of 3.33 g) were assigned to 21 net cages, with 120 individuals per cage and three cages per feed. Six formulated feeds, supplemented with 0%, 0.5%, 1%, 2%, 3%, and 5% CBC, were prepared and labeled as the control (Con), CBC0.5, CBC1, CBC2, CBC3, and CBC5 feeds, respectively. Additionally, dry Saccharina japonica was prepared to compare the performance of abalone fed with the formulated feeds. All abalone were fed once daily for 16 weeks. Following the 16‐week feeding experiment, 60 abalone from each cage were randomly chosen and evenly divided into 3 groups. These groups were then exposed to stressors: 20 h air exposure, 20 h high temperature exposure (30°C), and 12 h low salinity exposure (25 psu). The survival of abalone was checked for 5 days following these stress tests. The specific growth rate (SGR) of abalone fed all artificial feeds was statistically (p < 0.05) greater than that of abalone fed the S. japonica, but no statistical differences were observed among abalone fed the different formulated feeds. The shell length, width, and height, and soft body weight of abalone fed with all artificial feeds were statistically superior (p < 0.05 for all) compared to those fed with S. japonica. After the 5‐day observation period following 20 h air exposure or high temperature exposure at 30°C, the survival rates of abalone fed with CBC2, CBC3, and CBC5 feeds were statistically (p < 0.05) greater than those fed with S. japonica. Increasing the CBC inclusion level (0–5%) in feeds linearly enhanced the abalone survival under 20 h air and high temperature exposures. Therefore, CBC exhibited great potential as a stress reducer in abalone feed, and the inclusion of at least 2% CBC in formulated feeds is recommended to enhance abalone’s resistance to air and high‐temperature stressors.