Effects of Bacillus probiotic enzyme extract on growth and carcass biochemical composition of rainbow trout (Oncorhynchus mykiss) larvae

The present study was done to evaluate the effects of enzyme extract, produced by five species of probiotics Bacillus on growth and carcass biochemical composition of rainbow trout (Oncorhynchus mykiss) larvae with initial body weight of 0.583 ± 0.197 g (mean ± SD). The enzyme extract was produced by Bacillus probiotics in broth media with concentrations of 1 × 10^6, 1 × 10^7 and 1 × 10^8 CFU/100g and then it was added into the feed of rainbow trout larvae respectively. The results of larval biometry at the end of the study showed that the use of enzyme extract with the highest Bacillus concentration (1×10^8 CFU/100g) in T3 (20.02 ±3.77 g) significantly increased the growth (P<0.05). Also other growth parameters as specific growth rate and average daily growth showed significant differences (P<0.05). The study of carcass biochemical composition according to AOAC (1990) standard showed that T1 and T3 had the highest crude protein content and control had the lowest crude protein content. Also the experimental treatments showed the highest survival rate in comparison with the control (P