Effects of 3-thia fatty acids on feed intake, growth, tissue fatty acid composition, beta-oxidation and Na+,K+-ATPase activity in Atlantic salmon.

Atlantic salmon (Salmo salar) with an initial mass of 86 g were reared in 12 degrees C seawater for 8 weeks to a final average mass of 250 g. The fish were fed fish meal and fish oil-based diet supplemented with either 0%, 0.3% or 0.6% of tetradecylthioacetic acid (TTA), a 3-thia fatty acid. The specific growth rate (SGR) decreased with increasing dietary dose of TTA. The SGR of the group fed 0% of TTA (Control) was 1.8; that of the group fed 0.3% of TTA (TTA-L) was 1.7, and that of the group fed 0.6% of TTA (TTA-H) was 1.5. The mortality increased with increased dietary dose of TTA. The mitochondrial beta-oxidation capacity in the liver of fish fed the TTA diets was 1.5 to 2 times higher than that of the Control fish. TTA supplementation caused substantial changes in the fatty acid compositions of the phospholipids (PL), triacylglycerols (TAG) and free fatty acids (FFA) of gills, heart and liver. The percentages of n-3 fatty acids, particularly 22:6 n-3, increased in fish fed diets containing TTA, while the percentage of the saturated FAs 14:0 and 16:0 in the PL fractions of the gills and heart decreased. The sum of monounsaturated FAs in the PL and TAG fractions from liver was significantly higher in fish fed diets containing TTA. TTA itself was primarily incorporated into PL. Two catabolic products of TTA (sulphoxides of TTA) were identified, and these products were particularly abundant in the kidney. TTA supplementation had no significant effect on the activity of the membrane-bound enzyme Na(+),K(+)-ATPase.