en تخصصي Special پژوهشي Research <span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><span style="font-size:12.0pt"><span new="" roman="" style="font-family:" times="">The use of functional feed additives is a key strategy for improving growth performance, health status, and disease resistance in shrimp aquaculture. This study evaluated the effects of a brown macroalgae premix extract (MPE), composed of <i>Sargassum ilicifolium</i>, <i>Nizimuddinia zanardini</i>, <i>Padina australis</i>, and <i>Cystoseira indica</i>, in combination with the probiotic <i>Bacillus subtilis</i> (P), on growth performance, haemolymph chemistry, antioxidant capacity, and resistance to <i>Vibrio parahaemolyticus</i> in whiteleg shrimp (<i>Litopenaeus</i> <i>vannamei</i>). A total of 2,400 post-larvae (initial weight: 1.29 &plusmn; 0.28 mg) were randomly assigned to eight dietary treatments, including a control, MPE alone, probiotic alone at three inclusion levels, and combinations of MPE with each probiotic level, for 60 days. Shrimp fed the MPE+P2 and MPE+P3 diets showed significantly higher final weight, weight gain, and specific growth rate than the control and other treatments (p < 0.05). These groups also exhibited significantly elevated total haemocyte counts, while the MPE+P2 treatment resulted in the highest haemolymph protein level and the lowest glucose concentration (p < 0.05). Combined supplementation significantly enhanced superoxide dismutase and glutathione peroxidase activities and improved post-challenge survival against V. parahaemolyticus, with the highest survival rate observed in the MPE+P2 group. Overall, dietary supplementation with brown macroalgae extracts in combination with B. subtilis exerted synergistic effects on growth performance, immune-related haemolymph parameters, antioxidant status, and disease resistance in <i>L. vannamei</i>.</span></span></span></span> Brown macroalgae extract, Bacillus subtilis, Litopenaeus vannamei, Growth performance, Haemolymph parameters, Antioxidant enzymes, Disease resistance 41 70 http://injvr.com/browse.php?a_code=A-10-54-2&slc_lang=en&sid=1 P. Akbary paria.akbary@gmail.com 10031947532846001570 10031947532846001570 Yes Faculty of Marine Sciences, Fisheries group, Chabahar Maritime University, Chabahar, Iran A. Azdari pariaakbary@gmail.com 10031947532846001571 10031947532846001571 No Agricultural Research Educations and Extension Organization (AREEO), Iranian Fisheries Science Research Institute (IFSRI), Chabahar Offshore Fisheries Research Center, Chabahar, Iran S. Dutta pariaakbary1355@gmail.com 10031947532846001572 10031947532846001572 No Department of Marine Science and Fisheries College of Agriculture and Marine Sciences Sultan Qaboos University, P.O.Box 34, Al-Khoud 123, Sultanate Oman M. Mirbakhsh paak@gmail.com 10031947532846001573 10031947532846001573 No Iranian Fisheries Science Research Institute (IFSRI), Agricultural Research Education and Extension Organization (AREEO), P.O. Box: 14965/149. Tehran, Iran