Dietary folic acid requirement of juvenile abalone Haliotis discus hannai Ino

• Folic acid requirement of abalone was 2.62 mg/kg based on the weight gain rate.
• That requirement was 5.29 mg/kg based on the viscera folic acid concentration.
• Dietary folic acid did not significantly influence survival.
• Dietary folic acid did not significantly influence the soft body compositions.

A 16-week growth study was conducted to determine the dietary folic acid requirement of juvenile abalone (initial mean weight 482.2 ± 2.2 mg). Six semi-purified diets were formulated to contain graded levels of folic acid (0.06, 1.44, 2.86, 5.88, 14.27 and 35.71 mg/kg). Each diet was fed to three replicate tanks of abalone in a re-circulated water system. The results showed that the weight gain rate (WGR) was significantly increased when dietary folic acid contents increasing from 0.06 to 2.86 mg/kg (P < 0.05). Higher dietary folic acid (2.86–35.71 mg/kg) did not result in further increase of WGR. When dietary folic acid increased from 0.06 to 5.88 mg/kg, the viscera folic acid concentration (VFAC) significantly increased (P < 0.05). And then, there were no significant differences in VFAC among treatments as dietary folic acid contents increased from 5.88 to 35.71 mg/kg. Dietary folic acid did not significantly influence survival and the soft body compositions of abalone. Based on WGR and VFAC, broken-line analysis showed that dietary folic acid requirements of abalone were 2.62 and 5.29 mg/kg, respectively.