Influence of dietary fermented Saccharomyces cerevisiae on growth performance, oxidative stress parameters, and immune response of cultured Oreochromis niloticus Nermeen M. Abu-Elala & Nehal A. Younis & Huda O. AbuBakr & Naela M. Ragaa & Liliana L. Borges & Melina A. Bonato Received: 17 April 2019 /Accepted: 23 September 2019 # Springer Nature B.V. 2020 Abstract Our trial was performed to investigate the effect of fully fermented yeast Sacharomyces cerevisiae (Hilyses, ICC Company, Brazil) on the growth perfor- mance and immune response of Oreochromis niloticus. In this study, a total of 270 O. niloticus (50.7 ± 0.8 g) were randomly divided into 3 groups in triplicates. The control group was fed on the basal diet while the other two groups were fed on a basal diet supplemented with 0.2% and 0.4% of Hilyses. The trial period extended for 2 months. At the end of the feeding trial, oxidant and antioxidant parameters (MDA, catalase, and glutathione reductase), some innate immunological parameters and immune-related gene expression were measured. Histo- logical examination of liver, spleen, kidney, and intes- tine was performed. Further, fish groups were chal- lenged against Gram-negative and Gram-positive bacte- ria; A. hydrophila and L. garvieae. The results revealed significant improvement (p < 0.05) in growth perfor- mance and feed utilization in Hilyses-treated groups versus the control group. Blood parameters and liver and kidney functions of Hilyses-supplemented groups were similar to those of the control group. The histolog- ical findings of treated groups showed normal tissue structure with multiple focal lymphoid aggregations in the spleen, kidney, and intestine. Both levels of Hilyses successfully enhanced phagocytic activity/index, lyso- zyme activity, and gene expression of TNF-α, and IL- 1β. Fish group fed on 0.4% Hilyses exhibited the highest expression of IL-1β and the least mortality percentages post challenges. Thus, dietary supplemen- tation of Hilyses could promote the growth performance and immunity and increase the resistance of O. niloticus against diseases. Keywords β-Glucans . Nucleotides . Immunity . Growth . Challenge . O. niloticus Introduction The use of functional feed additives such as probiotics, prebiotics, synbiotics, herbal extracts, immunostimulants, nucleotides, and acidifiers has great impact on the global production of the commercial aquaculture all over the world (Naylor et al. 2000; Oliva-Teles 2012; Moffitt and Cajas-Cano 2014; Kobayashi et al. 2015; Abu-Elala and Ragaa 2015). Apart from boosting aquafeeds and safeguarding gener- al health of aquatic animals, they have been found to Fish Physiol Biochem https://doi.org/10.1007/s10695-019-00711-9 N. M. Abu-Elala (*) : N. A. Younis Department of Fish Diseases and Management, Faculty of Veterinary Medicine, Cairo University, Giza 12211, Egypt e-mail: nermeen_abuelala@cu.edu.eg H. O. AbuBakr Department of Biochemistry and Chemistry of Nutrition, Faculty of Veterinary Medicine, Cairo University, Giza 12211, Egypt N. M. Ragaa Department of nutrition and clinical nutrition, Faculty of Veterinary Medicine, Cairo University, Giza 12211, Egypt L. L. Borges : M. A. Bonato Research and Development Department, ICC Industrial Comércio Exportação e Importação Ltda., São Paulo 01451-909, Brazil