Effect of ration level and dietary docosahexaenoic acid content on the requirements for long-chain polyunsaturated fatty acids by juvenile barramundi (Lates calcarifer)

• DHA concentration nor the DHA:EPA ratio affected weight gain, growth rate or FCR of barramundi.
• Barramundi diets containing 1 g/kg DHA do not compromise growth or health status.

Juvenile barramundi were fed one of six diets containing differing docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) levels. Fish were restricted fed on a pair-fed feeding regime to eliminate variability in feed intake, with two diets fed to satiety to examine the effects of fixed or variable feed rations on EFA requirements. Weight gain, feed intake, feed utilisation, and physical clinical signs were monitored. No effect of dietary DHA and EPA concentration, DHA:EPA ratio or total LC-PUFA level was observed on weight gain, growth rate, feed conversion ratio (FCR), survival or physical clinical health signs (P > 0.05). Satiety fed fish had higher feed intake, final weight, weight gain and growth rate compared to their respective restrictively fed treatments (P < 0.05). No effect of ration level on the responses to DHA concentration was observed. Body fatty acid composition was affected by diet, increasing dietary DHA resulted in higher body tissue DHA concentration, and a similar relationship was observed for EPA. Plasma haemoglobin increased with increasing DHA + EPA levels (P < 0.05) while glutamate dehydrogenase increased for fish fed DHA + EPA in a 1:1 ratio, regardless of total dietary LC-PUFA (P < 0.05). Juvenile barramundi may be fed diets containing as low as 1 g kg− 1 DHA without compromising growth or health status.