62 MARCH 2014 • WORLD AQUACULTURE • WWW.WAS.ORG Effects of Linseed Oil Supplementation on the Nutrient Composition of Fillets of a Sturgeon Hybrid Acipenser ruthenus x Acipenser baeri J.Káldy, Á. Szilágyi , G. Szilágyi, L. Szathmári Diet can influence the chemical composition of fish fillets. The EPA and DHA fatty acids of the n-3 group induce biochemical changes that reduce the development of heart, cardiovascular, inflammation and proliferation diseases. These essential fatty acids are located primarily in fish oil (Husvéth et al. 1999). The n-3 group of fatty acids has an especially positive effect on the regulation of the plasma lipid level, for the cardiovascular system, immune functions and vision functions in humans (Jump 2002). The PUFA/SFA ratio is an essential criterium to quantify healthy meat products. The favorable ratio among SFA, MUFA and PUFA is 1:1.5:1 (Okuyama et al. 1996, Sugano 1996). Marine fish products are rich in n-3 fatty acids, but some freshwater species also have a favorable lipid composition. This is important for traditional fish consumers in countries where fish are supplied from inland fisheries and freshwater aquaculture. In Hungary, 52 percent of total fish consumption is derived from domestic catches and pond production (Szathmári et al. 2009). A study ws conducted to assess the effects of linseed oil supplementation on the nutritional content of hybrid sturgeon fillets. Study Methods Hybrids between Siberian sturgeon Acipenser baeri and sterlet Acipenser ruthenus were studied. Juveniles were raised at the Vasszécseny sturgeon laboratory in two RAS rectangular tanks with a volume of 2,500 L each. Flow rates to each tank were 46 L/min and the temperature varied between 18-20 oC. Each tank was aerated with a gas flow rate of 260 L/ min and dissolved oxygen levels were measured twice a day and varied between 6-8 mg/L. The stocking density was 35 fish/tank. The initial average body weight of hybrids was 265 g (Fig. 1). Experimental diets for sturgeon hybrids were a 45 percent crude protein, 15 percent crude lipid Aller Bronze sturgeon diet (Aller Aqua A/S) and the sturgeon diet supplemented with 5 percent linseed oil. The proximate composition of each diet is shown in Table 1. The feeding rate varied between 1.0-1.5 percent of body weight daily (Fig. 2). Fish were fed for 60 days, not including the 10-14 days required for fish to accept the diets. Fish were sampled every two weeks to adjust the daily food quantity. Sample fillets were examined according to the methods and rules of the Hungarian Food Codex 2004. Fatty acid composition was determined by gas chromatography at the Animal Nutrition Laboratory of Pannon University, Keszthely. Five samples of each TOP, FIGURE 1. Size of sturgeon hybrids at stocking. BOTTOM, FIGURE 2. Feeding by sturgeon hybrids in a tank.
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