A determination of the quantitative requirements for docosahexaenoic acid for juvenile barramundi (Lates calcarifer)

A series of diets with varying docosahexaenoic acid (DHA; 22:6n‐3) inclusion levels (1 g kg^?1 3 g kg^?1, 6 g kg^?1, 10 g kg^?1, 15 g kg^?1 and 18 g kg^?1) were fed to juvenile barramundi (Lates calcarifer) for 6 weeks. Two additional diets examined the addition of arachidonic acid (ARA; 20:4n‐6) or eicosapentaenoic acid (EPA; 20:5n‐3) to the diets at 10 g kg^?1 when DHA was also included at 10 g kg^?1. Fish were fed the diets on a pair‐fed feeding regime to eliminate feed intake variability. Fish were weighed, and blood and tissue samples were collected after 6 weeks. Behavioural parameters were also assessed. Improvement in growth was seen with increasing inclusion of DHA up to a maximum at 10 g kg^?1 inclusion, albeit the response was minor. However, the addition of ARA to the diet reduced the growth response, while the addition of EPA improved the growth response. An improvement in feeding behaviour was also seen with increasing DHA up to a peak at 10 g kg^?1, while those animals fed diets low in DHA showed increasingly cryptic behaviour. With the increasing inclusion of DHA, a range of pathologies were observed, but the addition of an EPA component to the diet limited these pathologies, while the addition of ARA made little improvement and in some cases exacerbated the pathologies.