Effects of using postbiotics in diet on growth parameters and antioxidant defense system in rainbow trout (Oncorhynchus mykiss) fingerlings

The aim of this research was to investigate the effects of different postbiotic levels on growth indicators, feed consumption and antioxidant defense system in rainbow trout (Oncorhynchus mykiss). For this purpose, rainbow trout fry (2-3 grams) were fed with experimental diets containing different levels (zero (control), 2, 4 and 8 grams per kilogram) of postbiotics for 8 weeks. At the end of the period, the growth indices and serum antioxidant defense system values were measured. Growth indices (average weight, specific growth rate, food conversion ratio, survival rate) were not significantly different between fish fed with postbiotic based on Saccharomyces cerevisiae yeast compared to the control group, although the increase in growth compared to the group The witness was observed. The highest numerical value of growth was obtained in fry fed with 8 grams of postbiotic per kilogram. Also, improvement of food conversion ratio was observed in fry fed with postbiotics. Although statistically, this decrease in food conversion coefficient was not significant. In all antioxidant factors, a significant difference was observed between the control group and the 8 g/kg treatment group. A significant difference was observed in the amount of catalase enzyme between the control group and the treatment group of 2 grams and 8 grams per kilogram. Also, similar results were observed regarding the activity of the superoxide dismutase enzyme, so that a significant difference was observed between the control group and the 8 gram treatment group. Regarding the glutathione peroxidase enzyme, a significant difference was observed only between the control group and the 8g/kg treatment, and the highest amount of this enzyme was observed in the 8g/kg treatment. According to the results of the present study, it can be concluded that the use of postbiotics based on Saccharomyces cerevisiae yeast in the diet of rainbow trout can be recommended to improve the growth indicators and also increase the capacity of the antioxidant defense system in rainbow trout.