| This study explored the nutritional physiological characteristics of Macrobrachium nipponense.The main contents include the determination of the optimal dietary protein to energy ratio, the optimal plant protein source to replace fish meal, and effects of dietary lipid sources on growth, body composition and ammonia nitrogen stress of juvenile fresh prawn. Moreover, the method of fatty acid beta oxidation rate was estabalished and the in vitro digestibility of five protein soucres as measured to support the above feeding trial.1. Effects of the dietary protein to energy ratio on growth, feed utilization and body composition in Macrobrachium nipponenseIn the present 8-week study, fish meal and casein were used as proteinsources. The lipid source was the mix offish oil and soybean oil (2:1 w/w). Corn starch was used as the carbohydrate source.Two-factor experiment was designed and nine semi-purified diets were formulated to contain three lipid levels (2%,8% and 14%) and three protein levels (33%,38% and 43%), producing P/E ratios from 16.49 to 23.42 mg/KJ protein. And we investigated the effects of dietary protein to energy ratio (P/E ratio) on the growth, feed utilization and body composition in juvenile M. nipponense (initial weight 0.304±0.003g). The results indicated that the survival rate ranged from 60-80%, and the growth indexes (including the growth, survival rate, and protein efficiency) were dose-dependently improved by the increased dietary lipid, but not dietary protein content. Increased dietary lipid content and/or protein content increased lipid accumulation in whole body, hepatopancreas, and muscle, but didn’t change the feed intake and hepatopancreas weight. Moreover, hepatopancreas was the main organization of its energy storage as seen from the the histological structure of tissue using H&E and Oil red staining. In conclusion, our present study indicated that M.nipponense is a species with relatively high energy requirement. It could utilize dietary lipid content up to 14%, while the dietary protein with more than 33% would not promote growth and protein efficiency. Taken together,33% dietary protein and 14% dietary lipid level with P/E ratio 16.49 could be optimum for M.nipponenseandwe could try to use low P/E ration feed in its actual aquaculture.2. The in vitro enzymolysis of five common feed ingrediens in Macrobrachium nipponenseThe digestive enzymes for the in vitro enzymolysis were extracted from hepatopanceas and intestine in Macrobrachium nipponense. The fish meal, soybean meal, cottonseed meal, rapeseed meal and peanut meal were digested for 8h by the digestive enzyme solutions at 37℃ and their digestibility were tested. The results showed that the digestibility of the fish meal, soybean meal, cottonseed meal, rapeseed meal and peanut meal, and dry matter and crude protein were 11.24%, 11.47%,12.33%,12.32%,8.73%,34.46%,43.67%,31.87%,36.63% and 32.55%, respectively. Soybean meal showed the highest digestibility in the in vitro assay, but the other four protein sources showed similar digestibility, which showed that the shrimp might have a high digestibility of soybean meal.3. The effect of different protein sources replacement of fish meal on growth and immunity in juvenile Macrobrachium nipponenseAfter understanding different protein source digestion rate, we respectively chose four plant protein sources (soybean meal, cottonseed meal, rapeseed mealand peanut meal) to replace 25% fish meal protein in five isonitrogenous and isocaloric diets,in order to further explore the nutritional effects of different plant sources in M. nipponense, full fish meal as control. After an 8-week trial, soybean and cottonseed meal indicated the ideal fish meal-replacing effects to promote growth and feed efficiency, and they even had a better growth performance than full fish meal, but the rapeseed and peanut meal significantly impaired the growth performance. The amino acid composition in diets and prawn muscles was comparable among groups. No significant differences were found among groups in the hepatopancreas and intestinal histological characteristics and activities of antioxidant enzymes. In together, soybean and cottonseed meals could be good candidates for fish meal replacement in M.nipponense, and the anti-nutritional factors existing in the rapeseed and peanut meals could be the reason to impair the nutritional values of the both meals.4. Effects of dietary lipid sources on growth, body composition and ammonia nitrogen Stress of juvenile fresh prawn Macrobrachium nipponenseBy the first part of this papper, we had known M. nipponense could accommodate 14% lipid level. To further explore suitable lipid source, four semi-purified diets containing different lipid sources (Palm oil, PO; Olive oil, OO; Safllower oil, SO; Perilla oil, PEO) were compared on growth, body composition and 24h ammonia nitrogen stress of fresh prawn, fish oil (FO) as control diet in a 56-day feeding trial. The best growth was observed in prawn fed FO and SO diets whereas SO diet fed prawn had the best feed utilization. There was no significant difference in HSI or crude lipid content among groups. But PL/TG ratio in hepatopancreas was significant different by further lipid analysis. The histological study of hepatopancreas showed no pathological changes. The fatty acid composition of muscle largely reflected that of the diets. Both MDA content and SOD activity were significantly different across lipid sources, and the significant increase was observed at SO diet compared with FO diet. In the 14h-60mg/L ammonia nitrogen stress test, SO diet had no difference with FO diet in the mortality percentage.Above all the experimental datas, safflower oil (SO) could be used as a suitable alternative lipid source offish oil in M. nipponense.5. The in vitro determination of fatty acid beta oxidation rate in Macrobrachium nipponenseTo further understand the ability of fatty acid breakdown in M. nipponense tissues, five kinds of fatty acids (palmitic acid, oleic acid, linoleic acid, linolenic acid, arachidonic acid) were chosen and tested. In this study, the labeled 14C was used as a substrate and serevel experimental parameters were optimized. The in vitro fatty acids β-oxidation system was firstly established in M. nipponense in the world. The results showed that:(1) P-oxidation rate of linolenic acid in hepatopancreas mitochondria was the strongest at 35℃ and the oxidizing rates of oleic acid, linoleic acid were followed. In peroxisomes, β-oxidation rates of linoleic acid and linolenic acid were the strongest. The same trend was found at 25℃. (2) β-oxidation rate of linoleic acid in muscle mitochondria was the strongest at 35℃. In muscle peroxisomes, β-oxidation rate of arachidonic acid was the strongest, followed by linoleic acid and linolenic acid. Arachidonic acid and linolenic acid obtained the maximum utilization in M. nipponense muscle mitochondria at 25℃. |
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