Effect of dietary supplementation of potential probiotic Weissella confusa on innate immunity, immune‐related genes expression, intestinal microbiota and growth performance of rainbow trout ( Oncorhynchus mykiss )

Abstract

Rainbow trout, Oncorhynchus mykiss (average initial weight: 115 ± 2.6 g), were fed with diets containing different levels of Weissella confusa (0 [control], 1.5 × 107 [T1], 3 × 107 [T2] and 4.5 × 107 [T3] CFU/g) for 2 months. At the end of the experiment, innate immunity, expression of immune-related genes, intestinal microbiota and growth performance of the fish were investigated. A significant increase (p < .05) was seen in the T2 group compared to other groups in terms of lysozyme activity. In case of alternative complement activity (ACH50), a significant increase (p < .05) was also observed in the T1 and T2 treatment groups compared to the other groups. The obtained data from the gene expressions showed a significant up-regulation of tumour necrosis factor-alpha (TNF-α) and interleukin 8 (IL-8) in W. confusa-fed fish (p < .05), while interferon gamma (IFN-γ) gene expression was only significantly up-regulated in T2. However, the expression of interleukin 10 (IL-10) was down-regulated in the supplemented treatments compared to the control group. Microbiological evaluation revealed that feeding with the W. confusa-supplemented diet significantly enhanced the lactic acid bacteria (LAB) levels (p < .05). Total bacterial count (TBC) was significantly increased in T2 compared to the control group (p < .05). Also, the growth performance of supplemented treatments remarkably improved compared to the control group (p < .05). These results confirmed the beneficial effects of W. confusa as host-derived potential probiotic in rainbow trout with the appropriate inclusion being 3 × 107 CFU/g.