Effect of dietary prebiotic on growth performance, blood parameters and gene expression of transforming growth factor beta1 in rainbow trout (Oncorhynchus mykiss)

This experiment was conducted to study the effects of two types of prebiotics A, contain 16% beta-glucans and 80% mannan-oligosaccharides, and B contain 30% beta-glucans and 18% mannan-oligosaccharides on weight gain, feed conversion ratio, survival rate, carcass percentage, blood parameters, gene expression of transforming growth factor beta1 (TGF-ß1) at head kidney and intestinal morphology of rainbow trout. One thousand eight hundred of fry rainbow trout (mean initial body weight 6 g) were randomly assigned to nine polyethylene tank (300 lit) which contained 200 fish per each tank. Fish fed daily at 3.5% of mass body weight by one of three dietary treatments containing control (without prebiotic), and experimental diets A and B for 8 weeks. The amount of probiotic in both experimental diets was 0.96 g.kg-1 which get by addition of 1 and 2 g.kg-1probiotic A and B, respectively. At the end of experiment, results showed that growth performance of fish was not affected by prebiotics supplement but carcass percent and survival rate of fish significantly increased by feeding prebiotics (p<0.05). The albumin, total protein and globulin of fish serum were significantly increased by prebiotics supplement (p<0.05) and supplementation of prebiotic B showed higher effects. The prebiotics supplement significantly increased blood lymphocyte and the ratio of length to high of intestinal villus of fish (p<0.05). The gene expression of TGF ß of head kidney was significantly increased by dietary prebiotics supplement (p<0.05) and prebiotic A increased the rate of this gene expression. In conclusion, the results of this experiment showed that using of dietary prebiotics A improved immunity and carcass efficiency of rainbow trout and physiological response of fish are related to probiotic composition.