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The influence of repeated defrosting on nutritional efficiency of Artemia salina nauplii for early developmental stages of fish
HULAN, Petr
Nutritional efficiency of deeply frosted and repeatedly defrosted zooplankton has not been totally clarified, and it is often questioned, however, the nutrients composition and effect of such deteriorated feed are missing. The aim of this study was to assess nutritional eddiciency of repeatedly defrosted nauplia Artemis salina, as well as changes in their chemical composition on the basis of the growth, survival and presence of the deformations in early ontogeny of Japanese medaka ( Oryzias latipes). The samples of fresh hatched artemia nauplii served as a control group. The experiment was carried out with samples of live nauplii, permanently frosted at -14°C, defrosted to 4°C and again frosted and defrosted to 25°C and frosted again. The larvae of medaka in the period of one week after shift to the exogenous nutrition were examined. Before the commencement of the experiment the composition of samples in terms of nutrient, amino acids and fatty acid contents was determined. The results proved that Oryzias latipes fed with live artemia not only grew better but also survived more that other fis in other treatments. No deformations were recorded Fish fed frozen food survived better than those fed with live Artemia. It was also found that fish fed live Artemia seems to be the highest however from the amino acid point of view it seems to be more appropriate to freeze it to -14°C, defreeze to 25°C and refreezing to -4°C. as for the fatty acids Artemia adjusted by the permanently freezing to -14°C. The processes of thawing and repeated freezing of artemia nauplii result in leaching of some nutrients but in the thickening of some others.
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The influence of repeated defrosting on nutritional effeciency of Artemia salina nauplii for Japanese medaka Oryzias latipes
HULAN, Petr
Nutritional efficiency of deeply frozen and repeatedly defrosted zooplankton is often questioned however, concrete data on the changes in the nutrients composition and effect of such deteriorated feed are missing. The aim of this work is to assess nutritional efficiency of repeatedly defrosted nauplii Artemis salina, as well as changes in their chemical composition on the basis of the growth, survival and malformation occurrence in the course of medaka ontogenesis. The samples of fresh hatched Artemia nauplii served as a control. The experiment was made with Japanese medaka larvae since their shift to exogenous nutrition using live nauplia, permanently frozen ( -25 °C), defrosted to 0 °C and frozen, and defrosted to +25 °C and frozen again. Before the commencement of the experiment and afterwards, food samples were analyzed for the composition in terms of nutrient content. The trials proved that Oryzias latipes fed frozen food survived better than those was fed live Artemia. It was also found that fish fed live Artemia grew better compared with those that were fed frozen brine shrimp. No malformations appeared in experimental fish. Nutritional value of Artemia is highest when supplied live. After adjusting shiver with some nutritional substances be reduced.
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