Dietary functional feed additives and their influence on the physiological development of crab species: current status, prospects, and future trends

The increasing global demand for high-quality seafood has accelerated the growth of aquaculture, leading to the widespread adoption of intensive farming systems aimed at boosting production and reducing pressure on wild stocks. However, these systems face sustainability challenges stemming from their dependence on fishmeal and soybean meal as primary protein sources, escalating feed costs, nutrient-rich effluents, and the overuse of antibiotics to control disease outbreaks. Such practices contribute to antimicrobial resistance, environmental degradation, and chemical residues in farmed organisms, underscoring the urgent need for more sustainable and health-oriented alternatives. In recent years, functional feed additives have emerged as promising substitutes for conventional ingredients. These additives, encompassing nutrient-based compounds (e.g., vitamins, minerals, essential fatty acids, carotenoids, and functional amino acids), and non-nutrient bioactives (e.g., chitosan, β-glucans, probiotics, prebiotics, plant and seaweed extracts, organic acids, essential oils, and natural binders), have been shown to significantly (p < 0.05) improve growth performance, immune responses, and antioxidant capacity in various crab species compared to control diets. Furthermore, several studies report enhanced gut morphology, stress resistance, and disease tolerance in treated groups (p < 0.05), highlighting their potential role in mitigating the adverse effects of fishmeal replacement and environmental stressors. This review critically synthesizes current evidence on the physiological impacts of dietary functional feed additives in crab aquaculture, elucidating their mechanisms of action, and evaluating their comparative efficacy based on statistical outcomes across studies. It also identifies existing knowledge gaps and challenges related to formulation optimization, additive standardization, cost-effectiveness, and large-scale application. Ultimately, this work underscores the prospects and future trends of functional feed additives as key tools for improving crab health, performance, and sustainability in modern aquaculture.