Folic acid is an essential vitamin for fish farming, and its shortage or extra-administration leads to physiological
dysfunctions and then, to decrease the production efficiency rate. This research studied the effects of two different
doses of folic acid (6 and 10 mg/kg dried food) on different biometric, hematologic and immunological parameters of
fingerling rainbow trout fishes (Oncorhynchus mykiss). Totally, we showed that both doses could improve different
biometric factors (except for condition index). Furthermore, despite the detrimental effects of these treatments on
red blood cells, they could improve immunological functions of the fishes. Since no differences have been observed
between the effects of these two folic acid doses, we concluded that treatment of this fish with 6 mg folic acid per kg
dried food was as efficient as treatment with 10 mg folic acid.
