FONTES DE ÃLEOS DA DIETA NA COMPOSIÃÃO DO MÃSCULO, LIPOPROTEÃNAS PLASMÃTICAS, IMUNIDADE INATA E RESISTÃNCIA DE TILÃPIAS DO NILO (Oreochromis niloticus L. 1757) / Dietary oil sources in muscle composition, plasmatic lipoprotein, innate immunity and resistance of Nile tilapia (Oreochromis niloticus L. 1757)

Milena Wolff Ferreira

The objetive of this study to determine the influence of some dietary fatty acids sources on the chemistry composition, fatty acids profile and total cholesterol in muscle; in cholesterol quantity, triglycerides and plasmatic lipoprotein; in some innate immunity functions; in hematopoiesis; and, in resistence of the Nile tilapia (Oreochromis niloticus L.) to Streptococcus agalactiae challenge. Hundred sixty sexed male Nile tilapia, with an initial average weight of 72 g, were randomly stocked in 20 circular tanks and maintained with a density of eight fish/tank. Fish were acclimated to laboratory conditions and fed with the different experimental diets for 160 days. The the treatments were composed for five semi-purified diets, isocaloric and isonitrogenous, contain approximately 32 % of crude protein and 3200 Kcal kg-1 of digestible energy. The composition of diets was the same except for the oil sources, what were added 5% the of soybean oil (SO), corn oil (CO), linseed oil (LO), fish oil (FO) and olive oil (OO). At the end of the feeding period, eight fish were randomly chosen from each tank, were anesthetized with benzocaine, and blood samples were collected by cardiac punction, to the cholesterol, triglycerides, plasmatic lipoprotein, hematocrit, osmotic fragility of the red blood cells, serum total protein, serum iro concentration and total iron biding capacity, serum bactericidal capacity, spontaneous haemolytic complement and serum lysozyme activity analysis. Subsequently, the fish were slaughtered to the chemistry composition, fatty acids profiles and muscle total choresterol analysis. The fish remainder continued receive experimental diet to challenge later. At experimental challenge, eight fish for tank, of all treatments were anesthetized and challenge by intraperitoneal injection with 0.1 mL of Streptococcus agalactiae inoculum (104 CFU fish-1). Fish mortality was recorded three times a day during 15 days. With relationship to the analyses of muscular composition no difference was found in the moisture, ash and total cholesterol muscle (P>0.05).The fish fed SO, CO and OO diets showed high percentage of ether extract compared to fish fed LO and FO diets (P<0.05). The high percentage of protein was found in fish fed FO diet (P<0.05). The fatty acids profiles was influenced by dietary lipid sources (P<0.05). The group fed SO and CO diets showed high level of C18:2 -6, while the fish LO diet showed high level of C18:3 -3, and the fish FO diet showed high level of C22:6 -3. With relationship to the sanguine parameters The fish fed FO diet showed high total cholesterol, HDL and LDL concentrations, and the fish fed SO, CO and LO diets showed high VLDL and tryglicerides concentrations (P<0.05). Regarding to hematological and immunological parameters, the percentage higher of hematocrit and serum total protein was in group fed SO diet (P<0.05). The higher resistance of erytrocytes was found in cell of fish fed LO and FO diets (P<0.05). The fish fed SO, CO and FO diets showed higher serum iron concentration and consequently low iron binding capacity (P<0.05). The activity of spontaneous haemolytic complement no influencied by dietary lipid sources (P>0.05). Only fish fed FO diet showed lower bactericidal activity and, the lower lysozyme activity was observed in the fish fed OO diet (P<0.05). The higth survival, after the experimental challenge, was observed in the fish fed SO diet, continued to fish fed LO and FO diets, and in the grup fed OO diet occured 100 % mortality. Concluded with this work what, the diets contained soybean, corn and olive oil higher the muscle lipid deposition; the diets contained fish and olive oil improve the lipoprotein standart; a dieta conteined soyabean oil improve in the immune functions and resistence of Nile tilapia against Streptococcus agalactiae challenge; and teh diets contained linseed, fish and olive oil were associated to immunosupression.

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