ISSN:
1749-7345
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
Studies on the nutritional physiology of larval fish should provide the basis for defining the length of the larval period and for understanding the quantitative and the qualitative feed requirements of the larvae. For these purposes, it is necessary to perform both descriptive investigations on the ontogenesis of structures and functions as well as experimental investigations on adaptive strategies of the larvae under changing feeding regimes. In the present communication, examples of both approaches are discussed comparing three species: African catfish Clarias gariepinus, whitefish Coregonus lavaretus, and turbot Scophthalmus maximus.At the onset of exogenous feeding, the digestive system of all three species is sufficiently developed to ensure efficient utilization of live food, but not of dry food. A major event during the subsequent development is the differentiation of the stomach. Evidence exists that for turbot and catfish, a functional stomach is necessary to utilize dry feeds as efficiently as live feeds. Therefore, from a nutritional point of view, in those two species the larval period, during which a special larval diet has to be given, ends with the completion of stomach differentiation.The capacity of the larvae to acclimate physiologically to different nutritional conditions seems to be limited. Using general nutritional indices such as protease activity, RNA/DNA ratio, midgut cell height or nuclear diameter of hepatocytes, larvae of the three species show partly starvation symptoms when reared on dry food. This effect can be explained to some extent by quantitative considerations, i.e., lower food consumption and digestibility is less for dry diets than for live diets. The contribution of the qualitative factors involved in the different performance of larvae reared on dry or live food is presently not well understood. Future studies should: 1) investigate why utilization of dry diets depends on presence of the stomach; 2) define more precisely the quantitative feed requirements of larvae; and 3) search those diet-induced qualitative differences of larval metabolism which affect growth performance.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1749-7345.1993.tb00001.x
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