Meat Quality Study With Commercial-size Farmed Sparus Macrocephalus

Fish flesh is rich in n-3 highly unsaturated fatty acid (n-3 HUFA) which is essential for human health. In comparison with terrestrial animal meat, fish flesh is recognized as beneficial to human health by decreasing cardiovascular and inflammatory disorders. Aquatic farming is growing apace because the wild fish caught from the sea can not meet the requirement of the market. However, reared fish present a low nutrition value and meat quality which result from manual aquatic condition. How to improve the meat quality of fish is an essential question in aquaculture. The purpose of the present study was to assess the relationship among dietary n-3 HUFA levels, dietary vitamin E levels and Sparus macrocephalus meat quality. Further more, we evaluated the possibility of using the fasting technique to manipulate the end product quality of Sparus macrocephalus and Pseudosciaena crocea. This dissertation was described in the following six sections.1 The influence of different dietary n-3 high unsaturated fatty acid (n-3 HUFA) levels on Sparus macrocephalus growth, fat deposition and lipid metabolismThe effect of dietary n-3 highly unsaturated fatty acid (n-3 HUFA) content on the lipid content and lipid metabolism were investigated in Sparus macrocephalus. Commercial-size Sparus macrocephalus were fed trash fish (D6 group) and five' formulated diets with 0.86%,1.93%,3.12%,3.86%和5% n-3 HUFA, respectively (D1-D5 groups) for 10 weeks. At the end of the experiment, the total body weight showed no significant difference among group (P>0.05). The hepatosomatic index (HIS) in group Dl was significantly higher (P<0.05) than other groups. Pervisceral fat content in group D1 was significantly higher (P<0.05) than that in group D5 and no differences were found among other groups. Hepatic lipid content in group D1 was significantly higher than those in group D2-D5.The content of triglycerides (TG), total cholesterol (TC) and glutamic-pyruvie transaminase activities in group Dl were significantly higher than other groups. In groups of D3-D6, the high density lipoprotein (HDL-C) was significantly lower than that in group Dl and no significant differences were found among other groups.2 The influence of different dietary n-3 HUFA levels on Sparus macrocephalus fatty acid compositionThe effect of dietary n-3 HUFA levels on muscle and liver fatty acid composition were investigated in Sparus macrocephalus. Commercial-size Sparus macrocephalus were fed trash fish (D6 group) and five formulated diets with 0.86 %,1.93%,3.12%,3.86%和5% n-3 HUFA, respectively (D1-D5 groups) for 10 weeks. At the end of the experiment, the content of EPA, DHA, C22:6n-3, C16:1 and C14:0 in muscle increased, while C16:1, C18:1n-9 and C18:2n-6 decreased with increasing dietary n-3 HUFA. The content of fatty acid in liver were not significantly affected by dietary n-3 HUFA levels.3 The influence of different dietary n-3 HUFA levels on Sparus macrocephalus antioxidant defence and lipid stabilityThe effect of dietary.n-3 HUFA levels on antioxidant defence and lipid stability were investigated in Sparus macrocephalus. Commercial-size Sparus macrocephalus were fed trash fish (D6 group) and five formulated diets with 0.86%,1.93%,3.12 %,3.86%和5% n-3 HUFA, respectively (D1-D5 groups)for 10 weeks. At the end of the experiment, hepatic activities of superoxide dismutase (SOD) and glutathione peroxidase (GPX) were significantly higher in group D1 than other groups. The flesh malondialdehyde (MDA) content were not significantly affect by n-3 HUFA levels (P>0.05). Fish fed with trash fish (group D6) had a higher muscle MDA level than groups D2-D5 but the difference were not significant (P>0.05).4 The influence of different levels of dietary a-tocopheryl acetate (Preslaughter diet) on Sparus macrocephalus flesh quality and vitamin E deposition The effect of dietaryα-tocopheryl acetate levels on flesh quality and vitamin E deposition were investigated in Sparus macrocephalus. Commercial-size Sparus macrocephalus were fed three formulated diets with 289mg/kg,553mg/kg and 1069mg/kgα-tocopheryl acetate, respectively (groups E250, E500 and E1000) for 8 weeks. At the end of the experiment, the growth, muscle proximate composition, muscle fatty acid composition and flesh malondialdehyde (MDA) content were not affected by dietaryα-tocopheryl acetate levels. Diet significantly (P<0.05) affected vitamin E in fillet in a dose-dependent manner, with fish fed the diet high inα-tocopheryl acetate incorporating (E500 and E1000) more than those receiving low level ofα-tocopheryl acetate (E250). Regressing analysis indicated a linear relationship between dietary and fillet concentration of vitamin E: y=9.19+0.0223x,r2=0.81 where y is the filletα-tocopherol content (μg/g), and x is the dietaryα-tocopheryl acetate content (mg/kg).5 The influence of different levels of dietaryα-tocopheryl acetate (Preslaughter diet) on Sparus macrocephalus antioxidant defense and shelf lifeThe effect of dietaryα-tocopheryl acetate levels on antioxidant defence and shelf life were investigated in Sparus macrocephalus. Commercial-size Sparus macrocephalus were fed three formulated diets with 289mg/kg,553mg/kg and 1069mg/kgα-tocopheryl acetate, respectively (groups E250, E500 and E1000) for 8 weeks. At the end of the experiment, the serum antioxidant enzyme activities showed some notable differences among the dietary treatment. The serum superoxide dismutase (SOD) activities and serum catalase (CAT) were significantly higher in Sparus macrocephalus with diets E500 and E1000 compared to E250. Serum glutathione peroxidase (GPX) activities did not change significantly among groups (P>0.05). The CAT:SOD ratio decreased with the elevated dietaryα-tocopheryl acetate levels. Tissue malondialdehyde (MDA) levels increased significantly (P<0.05) in Sparus macrocephalus during refrigeration and dietary treatment significantly affected flesh oxidation. The level of MDA was significantly (P<0.05) lower in fish fed high a-tocopheryl acetate supplemented diets (E500 and E1000) than those receiving low level of a-tocopheryl acetate (E250) on days 0,3,6 and 9. Tissue MDA levels did not change significantly between groups E500 and E1000.6 The influence of meat quality and antioxidant defenses of market-size Sparus macrocephalus and Pseudosciaena croceaThe effects of fasting on flesh composition and antioxidant defenses of market-size Sparus macrocephalus were investigated. Fish were divided into two groups (control and fasted) and reared in 6 cages. Group I fasted for 28 days; group II was fed normally as the control group. On 3,7,14,21 and 28 days,6 fish per group were sampled for analyses. In fasted fish, the reduction of lipid content in muscle occurred after day 3, and the content of protein decreased from day 14 compared to controls; the activity of liver anti-oxidative enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPX) increased from day 3 compared to controls; flesh malondialdehyde (MDA) levels increased from day 21 compared to controls.In Pseudosciaena crocea, the reduction of lipid content in muscle occurred after day 3, and the content of protein decreased from day 14 compared to controls; the activity of liver antioxidative enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPX) increased from day 3 compared to controls; flesh malondialdehyde (MDA) levels increased from day 21 compared to controls.