APPARENT DIGESTIBILITY OF LIPID AND FATTY-ACIDS IN RESIDUAL LIPIDS OF MEALS BY ADULT PENAEUS-MONODON

The apparent digestibilities of total lipid, lipid classes and individual fatty acids in the residual lipids from full fat soya, fish, squid, squid liver and fish liver meals were determined to assess the nutritive value of these meals to 20 g Penaeus monodon. Test ingredients were incorporated at 15% substitution levels into a reference diet. Chromic oxide was used as the inert marker. Residual lipids of these meals contained much higher levels of polyunsaturated fatty acids, especially n-3 type fatty acids, than equivalent oils. Triacylglycerols comprised 86.72% of total lipid in full fat soya as compared to 17.38 to 40.02% in the marine meals. Dry matter and total lipid digestibilities were highest with fish liver and squid liver meals. Triacylglycerols were fully digested (range 96.09-99.75%) in all meal lipids. The variability in apparent digestibility coefficients was high for free sterols (33.67-75.99%), steryl esters (23.23-93.95%) and free fatty acids (5.72-73.82%), but comparatively low for total phospholipids (60.19 to 94.12%). Mean values for individual fatty acids ranged from 53.79 to 99.94%. With the exception of squid meal lipid, the digestibilities of eicosapentaenoic and docosahexaenoic were not significantly different (P > 0.05) within meals.