Merican, Z.O., K.F. Shim-1996
Aquaculture, 147:275-291
Abstract:
The requirements of essential n-3 and n-6 fatty acids (EFA) for juvenile Penaeus monodon were assessed qualitatively in terms of weight and survival responses by feeding diets excluding each fatty acid separately. Purified diets contained 5% lipid mixture of 16:0 and 18:1n-9 (conditioning/control diet), 5% cod liver oil (reference diet) or 4.2% lipid mixture of 16:0 and 18:1n-9 and 0.8% mixture of four fatty acids of the five EFAs; 18:2n-6, 18:3n-3, 20:4n-6, 20:5n-3 and 22:6n-3. In a separate experiment, shrimp were fed diets with 1% 20:5n-3, 1% 22:6n-3 or 1% mixture of 20:5n-3 and 22:6n-3 added to a 4% mixture of 16:0 and 18:1n-9 as dietary lipid.
In both experiments, feeding the reference diet with 5% cod liver oil resulted in higher growth than diets supplemented with pure polyunsaturated fatty acids (PUFAs). In Experiment 1, weight gain of shrimp fed diets without supplements of 18:2n-6, 20:4n-6 and 20:5n-3 ranged from 275 to 301%. A requirement for pre-formed 18:3n-3 and 22:6n-3 was indicated by the significant declines (P < 0.05) in weight gain (189 and 195%, respectively) when shrimp were fed diets without these fatty acids. When fed the diet supplemented with only 1% 22:6n-3 as dietary EFA, weight gain of shrimp (359%) was significantly (P < 0.05) higher than of shrimp fed the supplemented with 1% 20:5n-3. However, the addition of 22:6n-3 to 20:5n-3 significantly (P < 0.05) improved growth. Survival responses were not related to qualitative differences n-3 and n-6 PUFAs supplemented into diets. Tissue levels of saturates and monounsaturates decreased with the supplementation of n-3 and n-6 PUFAs. No de novo synthesis of 18:3n-3 was evident. The chain elongation and desaturation of 20:5n-3 to 22:6n-3 and the retroconversion of 22:6n-3 to 20:5n-3 occurred. These results showed differences in the qualitative requirements of EFA and bioconversion capabilities of P. monodon as compared with other penaeids.
(Department of Zoology, National University of Singapore, Kent Ridge, 119260, Singapore)
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