Evaluation of phytase supplementation on the replacement of fish with soy flour on growth indices and some blood and biochemical parameters of serum free salmon (Salmo trutta caspius)

To determine the effect of phytase enzyme and replacement of fish flour with soy flour on growth process, and some blood and blood biochemical parameters of Caspian Sea fish with an average weight of 140.6 ± 13.7 gr, Seven diets with nitrogen and the same energy, containing different levels of soy flour (40 and 80%) for gradual replacement of fish powder (control diet without phytase enzyme), each with three levels of phytase enzyme (0, 1000 and 2000 International unit per kilogram) was prepared and fed to fish under the same conditions. At the end of the 12-week period of diet with experimental diets, gradual replacement of fish powder with soybean meal significantly reduced the growth and efficiency of fish food (P> 0.05). In addition, the addition of phytase enzyme significantly increased the growth and efficiency of food and the best result was obtained from the use of 2000 international units per kilogram of food. On the other hand, blood indices and serology of fish were also affected by diets. The amounts of liver enzymes with intermediate amounts of soybean meal had a direct relationship with the highest levels of alkaline phosphatase, alanine aminotransferase and aspartate aminotransferase in fish fed with high rations.. According to the results of this research, it is suggested that in the Caspian Sea salmon ration to be replaced by 40% of the protein content of fish flour with soy flour with 2000 units of phytase enzyme international unit per kg of food.