The alternative lipids tested lacked
n-3 LC-PUFAs, but contained high levels of SFAs, MUFAs, and/or C18
PUFAs. As expected, tissues of fish fed the alternative lipid-based feeds
began to more closely resemble the feeds themselves. For example,
fish fed C18 PUFA SOY and MUFA SOY feeds exhibited elevated deposition
of the eponymous fatty acids types, primarily 18:2n-6 and 18:1n-
9, respectively. Although less compositionally distinct, the POULTRY
feed contained less n-3 LC-PUFAs and more C18 PUFAs, MUFAs, and
SFAs, yielding similar shifts in tissue composition, particularly in the fillet
tissue. However, this effect was less overt with feeds containing
higher dietary levels of SFAs: the abundance of SFAs in the SFA SOY
and PALM feeds did not translate to proportional enrichment of these
fatty acids in the tissues (Fig. 2).
It is becoming increasingly evident that some fatty acids interfere
with the availability and tissue deposition of LC-PUFAs, whereas others
may have the opposite effect. In most cases, C18 PUFA-rich feeds appear
to reduce the availability and deposition of LC-PUFAs in the tissues.
Conversely, in some taxa, feed formulations rich in SFAs appear advantageous
in terms of maintaining tissue fatty acid profile (i.e., attenuating
reductions in LC-PUFA content typically associated with fish oil sparing/
replacement) and, in some cases, effectively reducing the amount of LCPUFAs
needed in the diet to satisfy requirements for these nutrients and
support tissue enrichment