Growth performance, hematological and immune parameters, and mRNA levels of cytokines and antioxidant-related genes in rainbow trout (Oncorhynchus mykiss) fed on Pediocuccus pentosaceus and/or ferulic acid

Abstract

The present study investigated the growth performance, blood parameters, and mRNA levels of growth, cytokines and antioxidant-related factors in rainbow trout (Oncorhynchus mykiss) that were fed with Pediocuccus pentosaceus (PP) and/or ferulic acid (FA). For this aim, 180 fish with initial body weight of 94.30 ± 1.77 g were fed on four experimental diets including the control (C), 108 CFU g−1P. pentosaceus (PP), 100 mg kg−1 ferulic acid (FA) and combination of both elements (108 CFU g−1 + 100 mg kg−1, PP + FA) for 8 weeks. The final weight, weight gain (WG), and specific growth rate (SGR) were found to be markedly affected by PP and FA, with the most substantial growth being observed in the PP + FA treatment (P < 0.05). The experimental diets had a significant impact on the feed conversion ratio (FCR), with the PP + FA treatment resulting in lowest FCR (P < 0.05). The hematological indices, namely RBC, WBC, Hct, and Hb, were not observed to be significantly impacted by the experimental diets (P > 0.05). The levels of total immunoglobulin, ACH50, and lysozyme were observed to be enhanced by the dietary FA and PP, with statistical significance (P < 0.05). The activity of Malondialdehyde (MDA) was found to be declined by the experimental diets, and its lowest value was considerably observed in the PP + FA treatment when compared to the control group (P < 0.05). It was seen that the fish which were provided with diets supplemented with PP and/or FA exhibited noteworthy increase in the activity of catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx), as compared to the control group (P < 0.05). The treatments which were fed with diets supplemented with PP + FA showed marked up-regulation in the expression of immune-regulatory genes, specifically IL1β, IL6, IL-8, and TNF-α, in contrast to the control group (P < 0.05). Significant upregulations were observed in the relative expression levels of SOD, CAT, GPx, and Glutathione reductase (GSR) genes in the experimental treatments that were provided with PP and/or FA (P < 0.05). In conclusion, it was shown that these dietary supplements at the optimal dosage have the potential to enhance growth, innate immunity, and antioxidant factors, genes associated with immunity and antioxidant systems in rainbow trout. Both feed supplements showed synergetic effects and it is recommended to employ these compounds simultaneously for sustainable aquaculture.