Effects of dietary b-glucan, mannan oligosaccharide, Lactobacillus plantarum and their combinations on growth performance, immunity and immune related gene expression of Caspian trout, Salmo trutta caspius (Kessler, 1877)

This study investigated the effect of individual and combination of dietary pre- and probiotics (beta-glucan, 3?mg/g; mannan oligosaccharide (MOS), 4?mg/g; and Lactobacillus plantarum; 10(8)CFU/mg diet) on growth performance, blood immune parameters, expression of immune related genes, and intestinal microbial of Caspian trout (Salmo trutta caspius). On the basis of feeding with immunostimulant diets, the fish were assigned into eight groups denoted as: control (basal diet), b beta (basal diet + beta-glucan), bM (basal diet + MOS), bLp (basal diet + L. plantarum), b beta Lp (basal diet + beta-glucan + L. plantarum), bMLp (basal diet + MOS + L. plantarum), bM beta (basal diet + MOS + beta-glucan), and bM beta Lp (basal diet + MOS + beta-glucan + L. plantarum). All of the immunostimulant diets, in general, reduced feed intake (FI) and food conversion ratio (FCR) and increased WG, PER, and final weight. Condition factor (CF) demonstrated the lowest level in the experimental group received bM beta Lp. Total lipid increased in the fish received the additives, especially bM and bM beta. Ash content demonstrated significant increase in the fish fed on b beta and bM beta Lp, whereas moisture content was reduced in the group fed with L. plantarum-supplemented diet. All immunostimulant diets enhanced the activity and levels of lysozyme, Immunoglobulin M (IgM), and serum alternative complement activity (ACH50); the highest value for these indices was observed in the groups fed with bM beta, bM beta Lp, and b beta Lp. bM beta-treated fish group displayed the highest cortisol and glucose levels. bM diet induced the highest mRNA transcription of TNF-a1 in head kidney, whereas bLp, bM beta, and bM beta Lp showed no effect. IL1 beta exhibited the greatest up-regulation, about 8.75 fold change, in response to the diet supplemented only with beta-glucan. b beta Lp and b beta significantly enhanced the relative IL-8 mRNA expression in the head kidney (about 2.75 and 1.9 folds, respectively), yet in response to bM beta Lp treatment it showed a decrease of about 5.7 times lower than the control group. In addition, intestinal population of L. plantarum showed the highest loads in the groups fed on the diets which were treated with the probiotic. Taken together, combinational use of these immunostimulants enhanced humoral innate immune system, whereas their individual and combinational application could increase and decrease the transcription of inflammation-related genes, respectively.