The Research Of Appropriate Lipid Source And Lipid Level Of Juvenile Russian Sturgeon, Acipenser Gueldenstaedtii, In Feed Nutrition

Russian sturgeon (Acipenser gueldenstaedtii), which is one of the earliest domesticated sturgeon, is a large economic cold water fish. Because of its great economic value, the farming scale of this fish has expanded unceasingly in our country recently, since it was introduced from Europe in the early of 1990s. However, studies of the nutritional requirements of Russian sturgeon are relatively rare, which cannot meet the demand of the industry of sturgeon aquaculture. As one of the three energy-yield source, dietary lipid can not only provide energy to fish directly, but also provide fish with essential fatty acids, and help fish absorb lipid-soluble vitamins. Therefore, this study explored the effects of dietary lipid level and source on the growth, physiological status, and biochemical response of Russian sturgeon with the aim to provide a reference and theoretical guidance for the preparation of the Russian sturgeon diets. The main findings of this study are as follows:1 Effect of different lipid source on growth, fatty acids profile and anti-oxidative status of juvenile Russian sturgeon A. gueldenstaedtiiAn 8 weeks feeding trial was conducted on the growth, whole body proximate compositions, fatty acid composition and anti-oxidation status in juvenile Russian sturgeon A. gueldenstaedti, fed diets with palm oil (PO), olive oil (OO), linseed oil (LO), sunflower oil (SO) and fish oil (FO) as lipid source, respectively. Each diet was randomly fed to triplicate tanks with 20 fish. The results showed fish fed PO diet had the highest weight gain, lowest hepatosomatic index and crude fat among all the groups (P<0.05).The final body weight, weight gain and specific growth rate of sturgeon fed LO diet were significantly lower than those of other groups (P<0.05). Fish fed the PO diet obtained the lowest feed conversion ratio, but there was no difference compared with OO group. The protein content of LO and SO group were significantly lower than the other, and the fat content of SO group was higher than other group but there was no difference with the 00 group. Fatty acid composition for the whole fish was closely correlated with those in diets. The fish of some groups, which did not contain the polyunsaturated fatty acid in diets, had a small amount of polyunsaturated fatty acid. The results declared that the Russian sturgeon had the ability to synthesize a certain amount of unsaturated fatty acid to meet the needs of the fish. The LO group obtained the higher malondialdehyde content than other groups. The fish fed PO and 00 diets obtained the lower superoxide dismutase activity than the fish fed LO、SO and FO diets. Comprehensive the growth, body composition, fatty acid composition and antioxidant performance, the palm oil could be used as good lipid source for juvenile Russian sturgeon to ensure the normal growth of fish and improve the oxidation resistance reducing the lipid per-oxidation.2.Effect of dietary lipid level on growth, blood biochemistry, lipid metabolism and anti-oxidative status of juvenile Russian sturgeon A. gueldenstaedtiiSeven isonitrogenousand isoenergetic diets containing lipid levels of 3%(L3),6% (L6),9%(L9),12%(L12),15%(L15),18%(L18) and 21%(L21) were formulated with equal combination of fish oil, soybean oil and linseed oil as the lipid source, and were fed to juvenile Russian sturgeon (6.20±0.02g) for 8 weeks. The results showed that fish fed L9 diet obtained higher final weight and weight gain than other groups except fish fed L6 diet (P>0.05). L9 diet had the highest protein efficiency and the lowest feed conversion ratio among all groups (P<0.05).The final body weight and weight gain of fish fed L18 or L21 diet were lower than fish fed L6 or L9 diet (P<0.05).The whole body crude lipid and hepatosmatic index increased with the increasing of dietary lipid level from 3% to 21%(P<0.05). Serum triglyceride, cholesterol, high-density lipoprotein cholesterol increased significantly with the dietary lipid level increasing (P< 0.05). These results suggested that excessive dietary lipid could not only slow down the fish growth and the protein efficiency of diet, but also cause the abnormal lipid deposit in liver. The lipoprotein lipase activity in liver increased as dietary lipid level increased, while the fatty acid synthase decreased, indicating that higher dietary lipid could promote the lipid metabolism in fish liver. The malondialdehyde content and superoxide dismutase activity in liver increased significantly with the increasing of lipid levels in diets (P<0.05).These results demonstrated that excessive lipid in diet could easily cause lipid per-oxidation. The optimal dietary lipid level for sturgeon was estimated as 8.77% by linear regression analysis based on weight gain.3 Replacement of dietary fish oil by palm oil on growth, lipid metabolism and anti-oxidative status on juvenile Russian sturgeon A. gueldenstaedtiiThe aim of the study is to investigate the effect of the replacement of fish oil with different proportions palm oil (100%,75%,50%,25% and 0%) on Russian sturgeon (A. gueldenstaedtii). Five experimental isonitrogenousand (crude protein was 42%) and isoenergetic semi-pure diets were formulated containing 9% lipid. Each diet was distributed to triplicate groups of 30 juvenile Russian sturgeons (initial body weight 6.20±0.02g) for 8 weeks. The results showed that the final body weight and weight gain were significantly higher in the group of 25% palm oil, but there was no difference with the 0% palm oil (100% fish oil) group. The 100% palm oil group got the lowest final body weight and weight gain, there was also no difference with the 100% fish oil group. The 25% palm oil group had the significantly lower feed coefficient than other groups (P<0.05).The results demonstrated that adding palm oil in the feed did not affect the growth of juvenile Russian sturgeon, the 25%palm oil group could significantly reduce feed coefficient and improve the feed utilization rate. The 25% palm oil group fish got the highest crude protein content but there was no difference with 100% fish oil group. The 100% fish oil group fish contained the highest crude lipid content. The hepatosomatic index of 100% palm oil group was significantly higher than 100% fish oil group. Under the level of 9% lipid, using the palm oil to replace fish oil could reduce the crude protein content of fish, increased the content of crude lipid which would affect the Russian sturgeon meat quality. The lipoprotein lipase activity in liver increased as palm oil increased in the diet, while the fatty acid synthase decreased. With the increasing content of palm oil in feed, the content of the malondialdehyde and the activity of superoxide dismutase reduced. Illustrating that the palm oil could remit the degree of lipid per-oxidation and increase the oxidation resistance of fish. Comprehensive the above results, palm oil can partly replace fish oil added to the Russian sturgeon larvae feed, the optimum adding proportion is 25%.