Supplementary Diet of DL‐Methionine and Electro‐N as Antistress to Improve Growth Rates and Immune Responses of Red Hybrid Tilapia ( Oreochromis mossambicus × Oreochromis niloticus ) Juveniles Reared Under High Densities

Abstract

Immunostimulantsare essential in aquaculture because they strengthen the immune system, enhance disease resistance, and improve the health of cultured aquatic species, especially under poor water quality and stressful conditions. They also promote better growth, survival, and antibody production without harmful side effects. As a safe alternative to antibiotics, immunostimulants support sustainable aquaculture and healthier fish farming practices. So, the current study was conducted to improve the performance of red tilapia fingerlings reared under stressful conditions of high densities by using commercial additives of methionine (MET) and a commercial antistress (Electro‐N, Elec). A 60‐day feeding trial including seven experimental diets was formulated as follows: a 30% crude protein basal diet without additives (T0), a basal diet supplemented with 0.5% MET (T1), 1.0% MET (T2), and 1.5% MET (T3). The same tested concentrations of MET with the addition of 0.5% Elec per (T4) 0.5% MET‐Elec, (T5) 1.0% MET‐Elec, and (T6) 1.5% MET‐Elec. Juveniles were within an initial average weight of 18.07 g ± 0.25 (SE) and randomly stored in 21 plastic tanks (60 L) at a rate of 20 fish/tank (60 fish/treatment). The data obtained suggested that dietary MET supplemented with or without Elec improved the growth, survival rate, and body content of protein, hematological characteristics, intestinal digestive enzymes, and immunity functions of fish in comparison with the control group. Specifically, a fish‐fed diet containing 1% MET with 0.5% Elec had a balance between the best survival rate and growth performance, indicating that this treatment had the best indicators of physiological and immunity functions.

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