Effects of organic microminerals (selenium, copper, and zinc) and mannan-oligosaccharides on the antioxidant and immune responses of Nile tilapia

Abstract

Individual use of organic trace minerals and mannan oligosaccharides promotes fish health. However, few studies have investigated their combined use, despite the possibility that these compounds may have additive or synergistic effects, resulting in greater benefits than their isolated application. Thus, we investigated the effect of Aquate Fish FT, a product combining selenium from yeast, peptide-chelated copper, peptide-chelated zinc, and mannan oligosaccharides, on gene expression related to the antioxidant and immune systems, liver antioxidant enzymes, leukocyte respiratory burst, total globulins, and growth performance in Nile tilapia after a four-week feeding period (Trial I). In addition, we evaluated the effects of Aquate Fish FT on liver antioxidant enzyme activities, leukocyte respiratory burst, total globulin levels, and growth performance after an eight-week feeding period (Trial II). In this second trial, fish were characterized before being subjected to an intraperitoneal challenge with endotoxin lipopolysaccharides extracted from Escherichia coli, administered at a dose of 500 µg kg⁻¹ in a volume of 0.2 mL per gram of fish, followed by sampling 24 h after the challenge. A total of 160 juvenile Nile tilapia (Oreochromis niloticus) (63.56 ± 4.41 g; mean ± SD) were fed isoproteic (30 % CP) and isoenergetic (4000 kcal GE kg⁻¹) diets containing four levels (0; 0.4; 0.8; and 1.2 %) of Aquate Fish FT and four repetition. The results showed that after four weeks, Aquate Fish FT promoted enhanced antioxidant and immune defenses, evidenced by upregulation of catalase (CAT) gene expression (P = 0.008), increased hepatic superoxide dismutase (SOD) enzyme activity (P = 0.021), upregulation of the immune cytokine interleukin 1β (IL-1β) (P = 0.002), and elevated leukocyte respiratory activity (P = 0.030). No significant differences were observed in the expression of superoxide dismutase (SOD2) (P = 0.181), glutathione peroxidase (GPx) (P = 0.192), interleukin 8 (IL-8) genes (P = 0.067), total globulins (P = 0,137), and growth performance (P > 0.05). After eight weeks, Aquate Fish FT significantly increased catalase (CAT) activity, with an even greater effect following lipopolysaccharide challenge (P = 0.012). Interestingly, leukocyte respiratory burst was reduced after lipopolysaccharide administration (P = 0.012), while total globulin levels increased (P = 0.028). In this trial, there was also no difference in growth performance (P > 0.05). Therefore, our results indicate that the combination of organic trace minerals (selenium, copper, and zinc) and mannan oligosaccharides (Aquate Fish FT) appears to modulate antioxidant and immunological parameters in Nile tilapia throughout different feeding periods.