Effects of Functional Additive Blend Containing Choline Chloride, L-carnitine, Glycerol Monolaurate, and Lysophospholipids on Protein Efficiency Ratio, Growth Performance, and Stress Tolerance in Juvenile Penaeus Vannamei

IntroductionFunctional feed additives are increasingly incorporated into aquaculture diets to improve nutrient utilization and production efficiency. However, their effects on growth, morphometric development, and stress resilience in shrimp remain incompletely understood.MethodsJuvenile whiteleg shrimp (Penaeus vannamei) were fed either a control diet or a diet supplemented with choline chloride, L-carnitine, glycerol monolaurate, and lysophospholipids for 42 days, using four replicate tanks per treatment. Growth performance, feed conversion ratio, protein efficiency ratio, growth uniformity, morphometric traits, length–weight relationships, growth dynamics, and responses to an acute low-salinity and temperature-shock challenge were evaluated.ResultsSupplementation significantly increased protein efficiency ratio compared with the control treatment (0.0237 ± 0.0008 vs. 0.0221 ± 0.0006; p = 0.019). Survival, final biomass, final body weight, feed conversion ratio, growth uniformity, final body length, modified condition factor, allometric coefficient, and stress-challenge survival were not significantly affected. Length–weight relationships indicated approximately isometric growth in both treatments. Multivariate analyses consistently identified protein efficiency ratio as the principal variable associated with supplementation.DiscussionThe additive blend improved apparent protein-use efficiency without substantially altering growth performance, morphometric development, growth dynamics, or stress tolerance. Nutrient-use efficiency may therefore be a more sensitive indicator of dietary additive responses than conventional growth metrics. However, the limited number of tank replicates and the combined osmotic and thermal stress challenge should be considered when interpreting the findings.