| Chinese mitten crab is one of the important crabs in China,it has important economic and nutritional value.In recent years,the crabs industry has spread over most areas of China,among which the Yangtze river basin has the largest scale of crab breeding.Due to the inbreeding of small-scale parents and the blind introduction and hybridization of different river crabs,the germplasm degradation of the Yangtze River pond cultured population increased at the precocious rate,the commodity crab size was small,and the disease resistance decreased.So it is especially important to genetically improve the crabs and breed new varieties with fast growth and strong resistance.Since 2000,relevant scientific research institutions in China have carried out several projects of crab genetic breeding,and a number of new varieties with advantages in growth traits have been selected and bred according to the breeding performance of river crabs,five of which have been approved by the National Fine Seeds Committee.In order to solve the problem of the crab market time too excessive concentration,Since 2010,the research group has conducted the breeding research on the early-maturing and late-maturing strains of Chinese mitten crab at the second-year,and now it has been bred to the fourth generation.This study evaluated the culture performance and nutrient composition of the second-year early-maturing and late-maturing strains of the fourth selective generation,in order to provide scientific basis and reference materials for the further development of breeding.1 The evaluation of culture and immunity performance of the secondyear early-maturing and late-maturing strains of the fourth selective generation during the juvenile culture of Chinese mitten crab(Eriocheir sinensis)The early-maturing(EM)and late-maturing(LM)of second-year E.sinensis have been mass selected to the fourth generation(G4),but their crabseed quality has not been evaluated.Therefore,this study was designed to compare the culture performance,immunity and disease resistance of EM,LM and non-selective crabseed(as the control)with the methods of culture experiment,challenge test and the analysis of non-specific immune indices.The results showed that:(1)The final weight and specific growth rate(SGR)of two selected populations were both relatively higher than the control,and the average weight of EM was lower than that of the LM between August and November,but no significant difference was observed.(2)In terms of culture effect,the order of survival rate and final yield was EM>LM>control with significant difference in yield of females,the order of precocious rate was opposite with significant difference in females either.(3)As for the immune index,the levels of alkaline phosphatase(AKP),acid phosphatase(ACP)and total antioxidant capacity(T-AOC)of two selected populations were higher than the control,with significant difference of ALP level in hepatopancreas of females and significant difference of T-AOC level in hemolymph of males;(4)Cumulative mortalities of two selected populations were both lower(29.50%and 22.94%,respectively)than the control in the challenge test.In conclusion,the crabseed quality of the two selected populations is more favorable,thus crabseed quality improvement of Chinese mitten crab seems feasible.2.The evaluation of culture performance of the second-year earlymaturing and late maturing strains of the fourth selective generation during the adult culture of Chinese mitten crab(Eriocheir sinensis)In this study,the culture performance and gonadal development of the fourth-generation early-maturing(EM)and late-maturing(LM)populations and the control group were compared by the culture experiment and the biopsy method.The results showed that:(1)The average weight and specific growth rate(SGR)of the two breeding populations in the culture experiment were higher than the control group,and the average weight of female was significantly higher than that of the control group(P<0.05),there was no significant difference between the males.(2)In terms of the percentage of crabs finished puberty molting,the changes of male and female in the three groups of crabs were similar.The puberty molt time of the EM group was earlier than that of the control group,and the LM group was slightly behind the control group,but there was no significant difference(P>0.05).(3)The difference of gonadal index(GSI)between the three groups of male and female crabs was consistent with the difference of genital crust velocity.The GSI of the EM group was always slightly higher than that of the control group,and theLM was always slightly lower than that of the control group.The hepatopancreas index(HSI)of the three groups of females showed a downward trend with the development of gonads,and there was no significant difference in HSI between the three groups of males.In conclusion,the Chinese mitten crabs of G4 generation has a significant improvement in growth performance and gonadal development,and has a good marketing prospects.3 The evaluation of nutritional quality of the fourth generation of earlymaturing and late-maturing populations of Chinese mitten crab(Eriocheir sinensis)in the stage of adult cultureThrough culture experiment and biochemical analysis,the tissue index,edible rate,routine biochemical indexes and fatty acid composition and content in edible tissues of the early-maturing(EM)and late-maturing(LM)group and the control group from the fourth generation were compared,the result showed than:(1)In terms of edible rate and tissue index of three groups,there was no significant difference in the male of three groups.The hepatosomatic index(HSI)of EM was higher than control group in female,and the gonadosomatic index(GSI)and total edible yield(TEY)were higher than the LM(P<0.05).(2)As for biochemical composition,the ovary's moisture of LM was highest,but lipid was lower than EM and control group(P<0.05),the three groups'biochemical composition of muscle and hepatopancreas have no significant difference.The muscle's protein and hepatopancreas'lipid of LM in male slightly lower than EM and control group,but there was no significant difference.(3)As for the fatty acid,male muscle fatty acid content only shows differences in several indicators.The highest content of?LC-PUFA was LM of female and control group of male,but there was no significant difference among the three groups.In female,the hepatopancreas of LM saturated fatty acids and polyunsaturated fatty acids were highest,especially the content of?LC-PUFA was significant higher than EM and control group.The ovary's polyunsaturated fatty acids content of EM were higher than others.No matter male or female,the C22:6n3,?PUFA and?LC-PUFA content were the highest in three groups.As a whole,the nutritional status of the two selected groups was significantly higher than that of the control group,especially female.After selective four generations for gonad development,its nutritional quality has also improved. |
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