Effect of vitamin C incorporation in live food on the larviculture success of aquaculture species.
1993
Merchie G. | Lavens H. | Sorgeloos P. | Nelis H. | Leenheer A. de
A study was undertaken to upgrade the levels of vitamin C in Artemia and Brachionus through bioencapsulation, and to investigate in this way the requirements for ascorbic acid (AA) during larviculture of fish and prawn. Ascorbyl palmitate (AP) was used as the vit C source because of its stable and lipophylic characteristics which allowed its incorporation in booster emulsions and its readily conversion into AA by Brachionus and Artemia. Under standard conditions very high levels of AA could be incorporated into the Artemia nauplii: supplementation of the enrichment emulsion with 20 per cent AP (w/w) increased the AA-content up to 2000 ppm after 24 h enrichment. Also in Brachionus the AA-level changed in function of the concentration of AA applied. 20 per cent AP in the diet enhanced the AA-content in the rotifers 10-fold over three days of culture. Using three different enrichment levels in the live food (0 per cent, 10 per cent and 20 per cent), no differences on growth nor survival could be observed for Macrobrachium rosenbergii under standard culture conditions. However, a significantly positive effect on the physiological condition of the postlarvae could be demonstrated when the vit C-boosted live food was administered. For Clarias gariepinus larvae fed vit C-boosted Artemia, supplemental dietary ascorbate resulted in a significantly positive effect on growth: the 20 per cent AP group weighed 30 per cent more then the control (0 per cent AP) on the final day of the experiment. Evaluation of the physiological condition showed a significantly higher resistance of the larvae according to the dietary vit C level. Dicentrarchus labrax larvae were successfully fed rotifers (day 4-12) and enriched Artemia nauplii (day 13-46), supplemented with the same three vitamin C levels. No significant differences in production characteristics nor in stress resistance of the fish larvae could be observed, however, for all salinity stress tests the 20 per cent AP group performed better. Comparing the results for the two aquaculture fish species, with those reported earlier for the larvae of the prawn Macrobrachium, it appears that the requirements for vit C are species specific, and might even differ according to the culture conditions.
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