Effects of dietary Lactobacillus casei on the immune, growth, antioxidant, and reproductive performances in male zebrafish (Danio rerio)

Abstract

In this study, the effect of different levels of Lactobacillus casei in the diet was examined on the expression of growth (IGF-1 and GH), immunity (TNF-a and Lyz), antioxidants (SOD and Cat), and reproduction-related genes (FSH-R, AR, and Activin). In this study, 600 juvenile zebrafish (Danio rerio) with an average weight of 0.15‌ ± 0.01 g in 4 treatments and three replications' groups were fed with a basal diet with three levels of probiotic Lactobacillus casei (105, 106, and 107 CFU/g) for six weeks. After sex determination, the males were fed with probiotic diets for two months. Our results showed that the probiotic fed groups significantly increased the total protein, total globulin, lysozyme in the group with 107 of L. casei with respect to the control group. The L. casei fed groups showed dose dependence significant differences regarding the weight gain (%) with respect to the control group (P < 0.05). Evaluation of gene expression of growth-related genes (IGF-1 and GH), immunity genes (TNF-a and Lyz), and reproduction genes (FSH-R, AR, and Activin) showed a significant increase in gene expression in probiotic-fed treatments compared to control treatment (P < 0.05). Evaluation of expression of genes related to the antioxidant activity (SOD and Cat) did not show a significant difference between probiotic-fed treatments compared to control treatment (P > 0.05). Our data represented the immunostimulants effect of from L. casei was regulated by induction of immune responses in zebrafish. Furthermore, L. casei probiotic strains can improve the development profile and reproductive performance in zebrafish, which confirmes the rationale of early administration of probiotics in aquaculture.