Influence of dietary phospholipid on early development and performance of Atlantic salmon (Salmo salar)

The present study aimed to confirm the requirement for dietary phospholipid in Atlantic salmon and better define the level and period of requirement. Thus, the effects of dietary supplementation with phospholipid supplied by krill or soy lecithin were investigated in Atlantic salmon, Salmo salar. First feeding fry were fed diets containing 55% protein and 17% lipid supplemented with krill oil or soybean lecithin in a regression design at five levels, 1.5 (unsupplemented), 2.6, 3.2, 3.6 and 4.2% total phospholipid and fish were sampled at 1g (1400°day post-fertilisation, dpf), 2.5g (1990°dpf), 5g (2350°dpf), 10–20g (2850°dpf) and smolt (3800°dpf). Survival was high overall with a positive correlation (r2=0.59–0.72) between survival and dietary phospholipid supplementation. Growth was improved by phospholipid with highest growth achieved in fish fed krill phospholipid at 2.6% and in fish fed soy lecithin at 3.6%. The pattern of growth differed between fish up to 2.5g and that from 2.5g onwards with SGR (0–2.5g) being significantly higher in fish fed 2.6% krill phospholipid and 3.6% soy phospholipid compared to the basal diet, whereas there was no difference in SGR (2.5g-smolt) between the treatments. Intestinal steatosis was observed in 2.5g fish fed the unsupplemented diet (20% prevalence) and lower levels of soy (10% prevalence), whereas it was absent from 2.5g fish fed krill oil and higher levels of soy lecithin (≥3.2%), and fish at all later stages. Prevalence of vertebral deformities was low but was reduced by increasing dietary phospholipid with krill oil generally being more effective. The results were consistent with salmon having a dietary requirement for dietary phospholipid in early life stages.