Effect of different levels of folic acid on growth performance and blood indexes of Beluga fingerling (Huso huso Linnaeus 1758)

Folic acid plays an essential role in promoting aquatic immune. In order to investigate the effect of folic acid diet on growth performance, carcass composition, blood parameters of 270 beluga fingerling with an average weight of 5-8 g with different levels of folic acid, including: 0.6 (as a control), 2.68, 3.72 and 4.84 mg/kg with three replications for 56 days were considered. The effect of experimental treatments on growth performance and immune indices was investigated. Results showed that the effect of treatments on feed conversion, specific growth rate, feed efficiency and weight gain was significant (P<0.05). Different levels of folic acid also made a significant difference in the number of white blood cells (P<0.05); So that the lowest value in the control treatment was 4.62 mg/kg and the highest was 6.75 mg/kg in the fourth treatment. There was a significant difference in the number of lymphocytes between the experimental groups, but no significant difference was observed in the number of neutrophils. After carcass analysis, as expected, increasing dietary folic acid level caused a significant increase in the percentage of crude protein in the carcass. So that the highest percentage of crude protein in the third treatment was 2.13 mg/kg. Moisture, fat and ash carcass indices were not significantly affected by experimental treatments. The results of this experiment showed that by increasing the amount of folic acid by 3.72 mg/kg, the fish will show better resistance in terms of immune and growth performance.