Folic acid is an essential vitamin in fish nutrition, and its lack or excessive intake may cause physiological disorders that reduce growth and production. Therefore, this study was conducted to evaluate the effects of different levels of folic acid (10, 20, 40, 80 and 160 mg/kg of dried rations) and compare it with the control group (0.0 folic acid) on the specific growth rate (SGR), weight gain (WG) and some physiological measurements in fingerlings of Nile tilapia; Oreochromis niloticus.
The experiment was designed in six groups in glass aquaria, each group in three replicates each with 10 fingerlings (20-30 g) after acclimation in laboratory conditions. Fish in each replicate was weighed and each group was fed with the processed feed to the extent of satiation twice a day for 8 weeks. At the end of the 8th week, fish weights were taken in each replicate separately to calculate the specific growth rate and weight gain. Blood samples were taken for physiological examinations.