Evaluation of the prebiotic GroBiotic®-A and brewers yeast as dietary supplements for sub-adult hybrid striped bass (Morone chrysops×M. saxatilis) challenged in situ with Mycobacterium marinum

Enhanced growth performance was generally observed in fish fed diets supplemented with GroBiotic®-A or brewers yeast compared to fish fed the basal diet throughout the feeding trial with significantly (P < 0.05) enhanced weight gain observed after 12 weeks of feeding. At the end of the feeding trial, fish fed 2% brewers yeast had significantly higher feed efficiency than fish fed the other diets. The in situ mycobacterial challenge employed in this experiment resulted in overall cumulative mortality of approximately 25%. Fish fed 2% GroBiotic®-A had a significantly (P < 0.05) enhanced survival (80%) compared to the other treatments (72-73%) at the end of 21 weeks. It is concluded that dietary supplementation of 2% GroBiotic®-A showed moderate but significant (P < 0.05) protection against mycobacterial infection. Dietary supplementation of partially autolyzed brewers yeast also may enhance growth performance under chronic infection of mycobacteria.