| As a protein source for aquatic animals , Soy Protein Concentrate (SPC) was systematically evaluated based on its content of nutrient and its effects on growth, body composition, digestive physiology, immune function, ammonia nitrogen and phosphorus excretion. The results were followed.1. Primary evaluation of SPC nutrition as a protein source for aquatic animalsThe potential of SPC was evaluated based on its biochemical compositions, including crude protein, lipid, moisture, carbohydrate, phosphorus and anti-nutritional factors. The results showed that, compared with fish meal and other protein source, soybean protein concentrate has a high level of crude protein, good profile and high level of amino acids, and low level of phosphors. Incorporation of soybean protein concentrate in the diet of aquatic animals will not contribute to reduce the pollution of aquaculture water, but also can lighten the urgency for shortage of fish meal in aquaculture diets.2. Effects of SPC as a Diet Protein Source on Growth and Body Composition of Eriocheir sinensisThe effect of SPC (SPC) as a partial or total replacement of fish meal (FM) was studied in Eriocheir sinensis. Six experiment diets containing a gradient of SPC were fed to duplicate group of crab over 50 days at 24±1℃. Crabs fed diets of total fishmeal and containing 0, 11, 22, 33, 44and 56% of SPC showed growth performance (Replacement of FM were 0, 18.64, 37.93, 56.90, 77.19, 100%, respectively), named diet 1-6. Diet 1 contained no SPC and served as control. Crabs fed the diets containing 22 and 44% of SPC had comparable growth performance as the crabs fed other diets, while total replacement of FM adversely affected growth. Survival rate increased with the increasing of SPC in the diet, and significant difference was observed between group 6 and the control (group 1) (P<0.05), whilefor the molt rate, it firstly increased and then decreased with the increasing of SPC in the diet, and it was significantly lower than group 6 (P<0.05); Weight gain, GBP, SGRW, and SGRL showed similar change as molt rate. Compared with the control, replacement of FM would reach 77.17% without adverse effect of growth, while according to the quadratic equation between replacement ratio and weight gain, the optimum replacement of FM by SPC for growth was 38.74%. FCR, PCR, PUR, FR firstly increased with the SPC content increasing in the diet, and then decreased, and significantly lower than the control (P<0.05). The results of body composition of Eriocheir sinensis showed that with increasing content of SPC in the diets, there was an increasing moisture and decreasing protein and lipid content. Protein content of crabs fed diet 5 and 6 were significantly lower than that of crabs fed with other diets (P<0.05), and lipid contents in crabs of group 4, 6 were significantly lower than that in control.3. Effects of SPC as a dietary protein source on nutrient metabolism of Eriocheir sinensisMeanwhile, the effects of SPC on digestive enzyme activities of Eriocheir sinensis were studied. The trypsin, pepsin, amylase, cellulose, lipase and muscle amino acids were measured on days 50 after initiation of feeding. There was a tendency of decreasing of pepsin and trypsin activities with the incorporation of SPC levels increasing in the diets. When incorporation of SPC level was up to 44% in the diets, significant decreasing of trypsin and pepsin specific activity were found in the juvenile crabs. Besides, there seemed to be a tendency of increasing of amylase activity, and a tendency of decreasing of cellulose activity with the increasing of SPC level in the diet. The increasing tendency of A/T ratio showed that with the increasing of SPC in the diets, Eriocheir sinensis had the tendency to be herbivorous, indicating that Eriocheir sinensis may have an adaptation to the different contents of fish meal and SPC, and it also supports that SPC can be used in the diet for Eriocheir sinensis.The blood chemistry and RNA: DNA ratios in different tissues were also studied. The results showed the total amino acids (TAA)...
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