Dietary folic acid requirement for maximum growth of juvenile tilapia Oreochromis niloticus x O-aureus

A feeding trial was conducted to estimate the dietary folic acid requiremen t of juvenile tilapia, Oreochromis niloticusxO. aureus. Purified basal diet s with eight levels (0.0, 0.3, 0.6, 1.0, 3.0, 6.0, 10.0, 20.0 mg/kg diet) o f supplemental folic acid were fed to tilapia (mean initial weight 0.41 +/- 0.01 g) for 8 weeks. Each diet was fed to three replicate groups of fish r eared in a closed recirculating system. Results indicated that weight gain and feed efficiency (FE) were significantly (P<0.05) greater in fish fed <g reater than or equal to>1.0 mg folic acid/kg diet than fish fed 0.3 mg foli c acid/kg diet or the unsupplemented control diet. Mortality of fish was no t affected by dietary treatment. Hepatic folic acid concentration increased with an increase in dietary folic acid and values were significantly highe r in fish fed greater than or equal to6.0 mg folic acid/kg diet than fish f ed the control diet. An analysis of the weight gain percentage by broken-li ne regression indicates that the adequate dietary folic acid requirement in juvenile tilapia is 0.82 mg/kg diet.