Combined and interactive impacts of octacosanol and Saccharomyces cerevisiae on growth, physiological responses, and disease resistance in whiteleg shrimp (Litopenaeus vannamei).

The development of functional feed additives represents a promising strategy to enhance shrimp performance and resilience in sustainable aquaculture. This study investigated the individual and combined effects of octacosanol and Saccharomyces cerevisiae on growth performance, physiological status, antioxidant capacity, immune response, and disease resistance in Litopenaeus vannamei. A total of 360 shrimp were randomly assigned to four dietary treatments in triplicate and fed for 60 days: a control diet, octacosanol (12 mg/kg), S. cerevisiae (4 g/kg), and a combined treatment (12 mg/kg octacosanol + 4 g/kg yeast). Disease resistance was further evaluated using a waterborne immersion challenge with the pathogenic Aeromonas hydrophila, with survival monitored over 10 days. All supplemented groups exhibited significantly improved growth performance, with OCTA×SC recording the highest final body weight, weight gain, and specific growth rate, alongside the lowest feed conversion ratio, relative to control (p < 0.05). Digestive enzyme activities, including lipase and protease, were significantly enhanced, particularly in the OCTA×SC group. Fatty acid profiling of both muscle and hepatopancreas revealed a significant reduction in saturated fatty acids and a concurrent increase in n-6 and n-3 polyunsaturated fatty acids, with DHA accumulation being most pronounced in OCTA×SC. Serum biochemical analysis demonstrated significant improvements in total protein, albumin, globulin, and HDL-cholesterol, alongside significant reductions in triglycerides and hepatic transaminase activities (AST and ALT) in supplemented groups. Antioxidant enzyme activities (CAT, SOD, GPx) and total antioxidant capacity were significantly upregulated, while lipid peroxidation (MDA) was significantly reduced, most markedly under combined supplementation. Transcriptional analysis confirmed significant (p < 0.05) upregulation of immune-related genes (HMC-Lv, Pen3-Lv, LZM-Lv, ProPO-Lv) and antioxidant genes (cMnSOD-Lv, CAT-Lv, GSH-Px-Lv) in all supplemented groups, with OCTA×SC consistently yielding the greatest induction. Following bacterial challenge, OCTA×SC exhibited the highest survival rate and relative percentage of survival (RPS = 43.48%), significantly exceeding single-supplement groups (RPS = 30.43% each). In conclusion, the synergistic application of octacosanol and S. cerevisiae (12 mg/kg octacosanol + 4 g/kg yeast) effectively enhances growth, physiological stability, and disease resistance in L. vannamei. These findings support the integrated use of octacosanol and S. cerevisiae as a synergistic nutritional strategy to enhance shrimp performance and disease resilience in intensive aquaculture systems. Future work should address mechanisms, dosage optimization, and long-term impacts on health and sustainability.