# Evaluation of Functional Marine Protein Hydrolysates as Fish Meal Replacements in Low-Fish-Meal Diets: Effects on Growth Performance, Feed Utilization, and Health Status of Asian Seabass (Lates calcarifer)

## TL;DR

This study shows that tuna protein hydrolysate can replace fish meal in seabass diets without harming growth or health, offering a sustainable alternative for aquaculture.

## Contribution

Tuna hydrolysate in soybean meal diets restores growth and stress tolerance in seabass, offering a sustainable fish meal alternative.

## Key findings

- Tuna hydrolysate improved growth, feed efficiency, and stress tolerance in low-fish-meal diets for Asian seabass.
- Intestinal health markers like villus length and goblet cell count improved with tuna hydrolysate supplementation.
- Survival rates under ammonia stress were higher in diets supplemented with tuna hydrolysate.

## Abstract

This study tested marine protein hydrolysates from seafood by-products as fish meal replacements in Asian seabass diets. Tuna hydrolysate, when added to soybean meal-based diets, restored growth, feed efficiency, and stress tolerance to levels similar to traditional fish meal diets. Intestinal health improved while other health indicators were unchanged. Tuna hydrolysate shows strong potential as a sustainable fish meal alternative for seabass farming.

An eight-week study was conducted to evaluate the effects of dietary marine protein hydrolysates as fish meal replacements in low-fish-meal diets on the growth performance, feed utilization, and health status of Asian seabass (Lates calcarifer). The high-fish-meal (HFM) diet contained 25% fish meal, while the low-fish-meal (LFM) diet replaced 60% of the fish meal with soybean meal. Three experimental diets were formulated by supplementing the LFM diet with 5% tuna hydrolysate (TH), 2% shrimp hydrolysate (SH), and 5% salmon silage (SS), each replacing an equivalent amount of fish meal. These diets were designated as LFM + TH, LFM + SH, and LFM + SS, respectively. The results showed that the LFM + TH diet significantly improved the percentage of weight gain, average daily growth, specific growth rate, protein efficiency ratio, and feed conversion ratio compared to the LFM diet (p < 0.05), without negatively affecting feed intake or metabolic markers. Histological analysis revealed improved villus length and goblet cell count in the intestine, indicating better nutrient absorption (p < 0.05). However, no significant differences were observed in hematological and immunological parameters, blood plasma metabolic markers, or carcass proximate composition (p > 0.05). Furthermore, the LFM + TH diet exhibited superior survival rates under ammonia stress, highlighting its potential to enhance stress tolerance. These findings suggest that marine protein hydrolysates, particularly 5%TH, can serve as a sustainable and efficient alternative to fish meal protein in diets with up to 60% in soybean meal compensation, promoting better growth and survival in Asian seabass.