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The intensive feeding of young stages of fish with dry starter feeds under controlled conditions commonly results in body deformities. Most often these are caused by deficits of the dietary minerals necessary for skeletal development. The present article is a review of the literature data concerning this issue. The most important minerals for proper skeletal mineralization are phosphorus, calcium, and magnesium. Their role in the physiology of fish and the demand for them are presented for various fish species, and the effects of deficiency are described. The most important reasons for shortages of these minerals in fish are also discussed.
The second part of this paper presents selected data from the literature on the causes of the development of body deformities in fish larvae and juveniles fed starter feeds under controlled conditions. The cause of severe body deformities include the hypovitaminosis of vitamins C, E, A, D, and K, and the hypervitaminosis of vitamin A. Of the amino acids, excesses of leucine or the lack and/or deficiency of tryptophan can cause skeletal abnormalities. Deficiencies of n-3 PUFA can cause similar effects, but only in larval fish.
The aim of the experiment was to determine the impact adding a vitamin-mineral supplement to feed had on selected rearing indexes of juvenile common whitefish (Coregonus lavaretus) during rearing in a recirculating system. The study material comprised juvenile common whitefish aged 4 months with an initial body weight of 5.2 g and body length of 7.6 cm. During the experiment, the feed applied was extruded juvenile feed T - 1.5 Nutra MP Trouv (France). The experiment comprised two dietary treatments: group K (feed without a supplement) and group M (feed with a vitamin-mineral supplement). The feed supplement used was the MIK 1 mixture (Mikita, Lublin-Zemborzyce). The quantity added was 10% of the extruded feed. During the experiment, significant differences were noted in fish growth and the feed conversion coefficient (P < 0.05). Individuals with body deformities were noted during the experiment; the deformities manifested primarily as the shortening of the operculum and mouth anomalies. The number of these individuals differed in the two groups, and by the end of the experiment the number of individuals with body deformities in group K was significantly higher (13.8% of all fish) than in group M, in which such deformities were noted in just 1.3% of the fish (P < 0.01). Based on the results, it was concluded that through the application of the vitamin-mineral supplement higher biomass growth was attained, feed conversion was better, and the number of fish with body deformities was lower. Thanks to this, the rearing results of juvenile common whitefish in recirculating systems was more effective.
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