Investigation of the probiotic effects of lactobacillus sakei 2-3 and Candida zeylanoides y12-3 strains in rainbow trout (Oncorhynchus mykiss, walbaum 1792)

This thesis aimed to evaluate individual and combined effects of candidate probiotic strains C. zeylanoides Y12-3 and L. sakei 2-3 on growth, hematological parameters, serum immunological parameters, serum biochemistry, histopathology, histomorphology, expression of genes related to immunity and antioxidant enzyme activities and disease resistance against L. garvieae in rainbow trout. For this, the fish were fed with 4 different feeds (control, L. sakei 2-3, C. zeylanoides Y12-3 and L. sakei 2-3+C. zeylanoides Y12-3) for 60 days. After the experiment, growth parameters, serum glucose levels, serum lysozyme activity, and expression of genes related to immunity and antioxidant status in fish were increased in the probiotic groups. Triglyceride levels were lower in the probiotic groups than in the control group, and serum ALT levels were not affected. Histopathological examinations revealed reversible changes in the foregut, anterior kidney and liver, especially in fish in the C. zeylanoides and L. sakei + C. zeylanoides groups and their observation frequency was moderate. The frequency of histological changes detected in the liver in the L. sakei 2-3 group was found to be rare.The villus width and the number of goblet cells increased in the foreguts of the fish in the probiotic groups, except for the L. sakei 2-3. However, respiratory burst activity, superoxide anion production, expression of genes related to immunity (IgM, IL-B1, lysozyme, TNF-α, HSP70) and antioxidant enzyme activities (GPX, GST, SOD) and survival after challenged with L. garvieae were higher in L. sakei group compared to the C. zeylanoides.