the effects of different levels of beta plus on growth performance, microbial flora and blood parameters of caspian trout, salmo caspius (kessler, 1877)

this study was conducted to evaluate the effects of beta plus probiotic, a mixture of bacillius leicheniformic and bacillius subtilis , on the growth performance and intestinal microbial flora of caspian trout ( salmo caspius ). a basal diet was formulated and supplemented with beta plus at 0, 0.5 and 1 g kg -1 , leading to three experimental diets. each experimental diet was randomly assigned to quadruple 1500 l tanks. the caspian trout with an initial weight of 108.7 ± 1.8 g were randomly distributed in the experimental tanks. the results showed that inclusion of dietary beta plus significantly increased the final weight and specific growth rate (sgr) of caspian trout compared to those the control treatment. the feed conversion ratio (fcr) was also improved significantly after probiotic administration to the experimental fish. however, the body composition and blood parameters were not influenced by the probiotic inclusion. total count of gram positive and negative bacteria in the intestine of the fish increased by feeding on diet contained 1 g kg -1 beta plus ( p <0.05). in conclusion, administration of the probiotic beta plus can improve the nutrient efficiency and growth performance of caspian trout confirming the positive effect of a mixture of bacillus spp.