Studies on FM replacement by alternative protein sources have not
always included data on the effects of FM sparing on fillet fatty acid
composition. Decreasing FM inclusion also reduces the amount of residual marine-origin lipid provided by this ingredient. The residual lipids
found in FM are primarily the phospholipid fraction, rich in LC-PUFA required by many marine carnivores. In diets containing little-to-no FO,
the FM-derived lipid may be particularly important in terms of meeting
essential fatty acid (EFA) requirements. In this study, despite the degree
of FM sparing attempted, no signs of EFA deficiency were observed,
suggesting that the LC-PUFA provided by the limited amount of FO
and S. limacinum included in the diet was adequate. Dietary lipid blends
contained more canola oil with increasing FM replacement, which
resulted in some differences in dietary lipid composition. Overall, fillet
fatty acid composition was reflective of dietary concentrations. Fillets
from all treatments were enriched in EPA and DHA relative to dietary
levels, indicating selective retention of these fatty acids as is typically
observed in fish (Trushenski et al., 2006)