Dietary Bacillus subtilis and macroalgae premix extract synergistically improve growth, digestive physiology, and gut integrity in whiteleg shrimp ( Litopenaeus vannamei )

This study evaluated the effects of dietary brown macroalgae premix extract (MPE) and Bacillus subtilis (BP) on growth performance, digestive enzyme activity, and intestinal health in whiteleg shrimp (Litopenaeus vannamei). A total of 2,400 post-larvae (29.1 ± 0.28 mg) were randomly distributed across eight treatments in triplicates for 60 days. Treatments included a control diet, 15 g kg−1 MPE, three BP concentrations (BP1, BP2, BP3: 1, 2, and 3 g 100 g−1), and their combinations. The combined use of MPE and Bacillus subtilis significantly improved growth performance and feed conversion ratio in shrimp fed MPE+BP2 and MPE+BP3 diets (p < .05). Higher digestive enzyme activity (lipase, amylase, protease) and greater intestinal fold length were observed in the MPE+BP2 treatment (p < .05). Dietary supplementation with MPE combined with 2 g 100 g−1 Bacillus subtilis represents a promising strategy to enhance growth, digestive function, and intestinal integrity in whiteleg shrimp.