Performance evaluation of combined probiotic Bacillus and yeast Saccharomyces cerevisiae isolated from the digestive tract of Huso huso on growth factors and biochemical body extracts improvement and increased resistance of Silver Carp (Hypophthalmichthys molitrix) larvae in the face of stressors

The aim of this study is determine the combined effects of probiotic: B. licheniformis and B. subtillis and a yeast species that called Saccharomyces cerevisiae that isolated from gut Beluga (Huso huso) on growth factor، biochemical factors in the body extract، and the amount resistance of silver carp larvae (Hypophthalmichthys molitrix) (The mean weight 200±15 mg) against environmental stressors. Control fish were fed with basal diet and other experimental groups of fish were fed with supplement diet in three concentration 1. 5×106 (T1)، 3×106 (T2) and 4. 5×106 (T3). Results showed that after 30 days of feeding the probiotic treatments، growth parameters significantly was increased (P<0. 05). T2 and T3 treatments have significantly better growth with less Feed conversion ratio (FCR) than the control group and specific growth rate (SGR) in this treatment had the best performance. Results showed that lipase levels in all four groups was not significantly change (P>0. 05). Amylase levels in T2 and T3 respectively and sugar in T3 showed the highest value. Cortisol levels in the control treatment were significantly greater than the groups that fed whit probiotic supplement (P<0. 05). Larvae fed diets containing the probiotic showed more resistance against unfavorable environmental conditions compared with the control group (P<0. 05). The results of this experiment showed that the probiotic mixture in a food supplement، on growth factors، biochemical factors in the body extract and resistance of Silver carp larvae in most cases will affect.