Coutteau, P.
Abstract:
Micro-algae, rotifers (Brachionus plicatilis) and brine shrimp (Artemia sp.) constitute the major components of the food chain in the intensive larviculture of commercially important species of fish, shrimp, and molluscs. The nutritional value of these live preys is very different from that of the natural food and various approaches have been developed to either improve the nutritional value of live feeds or supplement/replace the live feed with artificial diets. The techniques that may have relevance for the manipulation of dietary lipids, fatty acids and vitamins in zooplankton are reviewed in this paper. The major limitations and drawbacks of the various live food organisms, including variability of their biochemical composition, complexity, cost and availability, are illustrated for micro-algae, rotifers and Artemia. The improvement of live preys is based on the technique of bio-encapsulation, i.e. the enrichment of live feed organisms through feeding with micro-particulate diets that are rich in the target nutrient. The insufficient levels of essential fatty acids, in particular (n-3) highly unsaturated fatty acids (HUFA:EPA, 20:5n-3, and DHA, 22:6n-3) in the cultured live preys can be alleviated by enrichment with micro-algae and/or a variety of micro-particulate diets rich in (n-3) HUFA. Although enrichment has resulted in a major advance in the success of hatcheries of marine fish and shrimp, the understanding of the HUFA requirements remains limited due to the restricted possibilities to manipulate the live feed composition (e.g. HUFA and lipid composition). Vitamin enrichment in live feed is easily achieved using emulsified diets for lipid-soluble vitamins (vitamin D, A) or lipophilic forms of water-soluble vitamins (vitamin C palmitate), whereas liposomes are potentially interesting as carriers for water-soluble vitamins. The various supplementation/replacement diets for live feed organisms are reviewed and illustrated with two case studies, i.e. the replacement of live algae by yeast in the culture of Artemia franciscana and the supplementation of essential fatty acids to live algae in bivalve larvae.
(Laboratory of Aquaculture & Artemia Reference Center, Ghent University, Rozier 44, B-9000 Gent, Belgium)
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