Limited effects of short-term dietary L-glutamate supplementation on intestinal morphology of 100 g hybrid striped bass (

Introduction: The aquaculture industry has been exploring new methods to enhance fish production, including using amino acids as supplements to boost growth and health. L-glutamate (Glu) is one of the most abundant amino acids in both animal and plant protein sources, but it has been considered nutritionally non-essential in fish diets because it can be produced endogenously. We recently reported that dietary supplementation of Glu within a purified amino acid diet increased growth in non-immune challenged hybrid striped bass that were 25 grams and modulated intestinal mucosal immunity that were immune stimulated. Although this shows that Glu can be an effective immunonutrient, no studies have assessed its effects on larger hybrid striped bass. This study aims to evaluate the impact of dietary supplementation of Glu on 100-gram hybrid striped bass that were not immune stimulated, testing the hypothesis that increasing amounts of Glu added to a purified diet would improve growth and intestinal morphology. Methods: Purified diets containing 0%, 1%, 3%, 5%, and 8% Glu were fed to 100 g hybrid striped bass for four weeks and compared with a group fed 60% fishmeal serving as a baseline control group. After the dietary intervention, serum and mucosa samples were analyzed to assess amino acid concentration, while middle intestine samples were evaluated histologically. Results: Four weeks of Glu supplementation did not have an effect on growth performance in 100 g fish, where all groups increased in weight by approximately 16% (P > 0.05). Intestinal mucosa Glu concentration increased with dietary level, reaching about 15.7 nmol per mg of tissue in fish fed 8% Glu (P < 0.001). Modest effects were seen in the decrease of goblet cells per villus in fish fed 0% Glu (P < 0.05), but there were no differences in intestinal morphology among the groups (P > 0.05). Discussion: While purified diets may not be an effective approach to improve growth or intestinal morphology in these hybrid striped bass, Glu may still be necessary for goblet cell abundance. Further research is warranted to inform amino acid supplementation strategies for specific developmental stages to achieve cost-effective growth and disease resistance.