Marine lipids
per 100 g of tissue. Total lipid extracts were fractionated into neutral
lipids and phospholipids on silica cartridges as described by Juaneda
& Rocquelin (1985). Neutral lipids (triglycerides) were quantified by
weighing and phospholipids by phosphorous determination (Bartlett,
1959). Phospholipid classes were separated using normal phase HPLC
method according to Leseigneur-Meynier & Gandemer (1991). Phospholipids were quantified with an evaporative light scattering detector
(DDL 10, Cunow). Individual phospholipid classes proportions were
expressed in percentage of total phospholipid content. Fatty acid compositions of triglycerides and phospholipids were determined by gas chromatography of methyl esters as described by Leseigneur-Meynier &
Gandemer (1991). The results were expressed as percentage of the total
methyl esters present.
Data were subjected to a two-way variance analysis. The model included
two factors (diet, 2 levels and transfer in sea water, 2 levels) and the interaction diet-transfer. Interactions were not detailed because this factor
showed no significant effect on most of the parameters.
Results and discussion
Results regarding the effects of dietary lipids and transfer in sea water
are presented separately because the interactions between these two
factors were not significant in most of the cases.
Effect of dietary fat
Dietary lipids had no significant effect on total lipid, triglyceride and
phospholipid contents of all the tissues (data not showed). Dietary lipids
had a weak impact on phospholipid composition (table 1 ). Compared
to fish oil diet, diet with maize oil induced an increase in PI proportion in gills and intestine ( + 0.4 to +0.7%) and a decrease in PI proportion in liver (-1.4%) and in SPM proportion in intestine and light
muscle (-0.3 to -0.8%). The fatty acid composition of triglycerides and
phospholipids reflected those of dietary lipids. Compared to hsh oil diet,
diet with maize oil induced an increase in total polyunsaturated fatty
acid (PUFA) proportion in both lipid fractions as a consequence of an
increase m (n-6) PUFA proportion, mainly as the linoleic acid which is
the main fatty acid of maize oil (tables 2, 3). This increase was balanced by a corresponding reduction in monounsaturated fatty acid (MUFA)
and (n-3) PUFA proportions.
The FA composition of tissues reflected to a large extent that of dietary FAs, confirming previous results on salmonids (Bell et al., 1991;
Greene & Selivonchick, 1999). The presence of increased proportion of
C20 (n-6) fatty acids in phospholipids of trout fed maize oil diet indicated that trout elongated 18:2 (n-6) into long-chain PUFAs through
142
per 100 g of tissue. Total lipid extracts were fractionated into neutral
lipids and phospholipids on silica cartridges as described by Juaneda
& Rocquelin (1985). Neutral lipids (triglycerides) were quantified by
weighing and phospholipids by phosphorous determination (Bartlett,
1959). Phospholipid classes were separated using normal phase HPLC
method according to Leseigneur-Meynier & Gandemer (1991). Phospholipids were quantified with an evaporative light scattering detector
(DDL 10, Cunow). Individual phospholipid classes proportions were
expressed in percentage of total phospholipid content. Fatty acid compositions of triglycerides and phospholipids were determined by gas chromatography of methyl esters as described by Leseigneur-Meynier &
Gandemer (1991). The results were expressed as percentage of the total
methyl esters present.
Data were subjected to a two-way variance analysis. The model included
two factors (diet, 2 levels and transfer in sea water, 2 levels) and the interaction diet-transfer. Interactions were not detailed because this factor
showed no significant effect on most of the parameters.
Results and discussion
Results regarding the effects of dietary lipids and transfer in sea water
are presented separately because the interactions between these two
factors were not significant in most of the cases.
Effect of dietary fat
Dietary lipids had no significant effect on total lipid, triglyceride and
phospholipid contents of all the tissues (data not showed). Dietary lipids
had a weak impact on phospholipid composition (table 1 ). Compared
to fish oil diet, diet with maize oil induced an increase in PI proportion in gills and intestine ( + 0.4 to +0.7%) and a decrease in PI proportion in liver (-1.4%) and in SPM proportion in intestine and light
muscle (-0.3 to -0.8%). The fatty acid composition of triglycerides and
phospholipids reflected those of dietary lipids. Compared to hsh oil diet,
diet with maize oil induced an increase in total polyunsaturated fatty
acid (PUFA) proportion in both lipid fractions as a consequence of an
increase m (n-6) PUFA proportion, mainly as the linoleic acid which is
the main fatty acid of maize oil (tables 2, 3). This increase was balanced by a corresponding reduction in monounsaturated fatty acid (MUFA)
and (n-3) PUFA proportions.
The FA composition of tissues reflected to a large extent that of dietary FAs, confirming previous results on salmonids (Bell et al., 1991;
Greene & Selivonchick, 1999). The presence of increased proportion of
C20 (n-6) fatty acids in phospholipids of trout fed maize oil diet indicated that trout elongated 18:2 (n-6) into long-chain PUFAs through
142