Potential use of whey protein as a partial substitute of fishmeal on growth performance, non‐specific immunity and gut histological status of juvenile European seabass, <i>Dicentrarchus labrax</i>

Abstract

Fishmeal (FM) replacement with new cost-effective protein sources becomes an imperative need for maintaining the continuous and sustainable development of aquaculture. Therefore, the present study investigated the effect of FM substitution with whey protein (WP) on growth, feed utilization, non-specific immunity, liver and kidney functions, and gut histological status of European seabass, Dicentrarchus labrax, juveniles. A total of 300 seabass juveniles (62.12 ± 0.40 g) were allocated into five treatments (three replicates each) representing 0%, 15%, 30%, 45% and 60% FM substitution by WP. The fish were reared in hapa net-cages (water volume 0.8 m) and fed the experimental diets for 10 weeks. The results revealed that WP could replace up to 45% of dietary FM without compromising growth, feed utilization and survival. However, the increasing in the substitution level up to 60% significantly decreased all performance criteria of the seabass. The response of seabass to FM replacement with WP in terms of weight gain follows a polynomial regression pattern with R2 = 0.7695. The total immunoglobulin and complement 3 levels in the plasma of seabass significantly improved with a substitution level that ranged between 15% and 30% of FM. The liver function enzymes and kidney function indicators remarkedly increased with increasing WP incorporation levels. The histological investigation of the seabass intestine and liver tissues indicated an increase of histopathological signs with high levels of FM substitution by WP. In conclusion, WP could replace up to 45% of dietary FM in the diet of European seabass juveniles without compromising growth and physiological performance.