| At present,compound feed and chilled fish are the two main feeding modes for crab farming.With the optimization of feed formula and the improvement of feed technology,the quality of compound feed has been greatly improved.However,chilled fish is still in the crab farming process.used in.Therefore,this experiment chose to study the effects of compound feed and chilled fish on river crabs during the overwintering period,the adult crab fattening period and the adult crab hoarding period.In order to replace chilled fish with compound feed in the process of river crab breeding,it can provide a certain reference for the optimization and improvement of compound feed.1.Effects of Compound Feed and Chilled Fish on Survival,Nutritional Composition,Digestion and Immunity of Eriocheir sinensis during overwinteringIn this experiment,the survival rate,nutritional composition,digestive enzymes,antioxidant enzymes and immunity of the juvenile Chinese Mitten Crab were studied without feeding(NF group),feeding compound feed(CF group)and feeding chilled fish(CTF group)during wintering.The results showed:(1)At the end of overwintering,the weight gain rate and hepatopancreas index of CF group and CTF group were significantly higher than those of NF group(P<0.05),and there was no significant difference in survival rate;(2)After overwintering,the fat and carbohydrates in the body and hepatopancreas of CF group and CTF group were significantly higher than those in NF group(P<0.05),while the water content in hepatopancreas of NF group was significantly higher than that in CF group and CTF group(P<0.05),the CF group had higher fat and carbohydrate content.Regardless of feeding or not,the protein content in the body decreased significantly,while the protein in the hepatopancreas increased significantly(P<0.05);(3)In the fatty acid composition,the content of C18:2n6 in the body and hepatopancreas was significantly higher in the CF group than in the NF group and CTF group,while the C20:5n3(EPA)and C22:6n3(DHA)contents in the CTF group were significantly higher than those in the NF group and CF group(P<0.05);(4)After overwintering,the activities of pepsin and α-AMS in the CF group were significantly higher than those in the NF group and CTF group(P<0.05);(5)Antioxidative ability of crab,the activity of SOD in hepatopancreas and serum of NF group was significantly higher than that in CF group and CTF group(P<0.05),and the activity of T-AOC in CF group was significantly higher than that in NF group and CTF group(P<0.05).),the MDA content in serum and hepatopancreas of female crabs in CTF group was significantly higher than that in NF group and CF group(P<0.05);(6)The immune ability of the crab,the activities of ACP and AKP in the CF group were significantly higher than those in the NF group(P<0.05).To sum up,compound feed should be properly fed during wintering of Chinese mitten crab,and the survival rate,hepatopancreas index,weight gain rate and nutrient accumulation of mitten crab under this feeding mode are better than those fed chilled fish,and feeding compound feed can be beneficial to the digestion of the crab,and enhance the anti-oxidation and immunity of the crab.2.Effects of compound feed and chilled fish on nutritional quality of Chinese mitten crab fatteningIn this experiment,the Chinese mitten crab was fattened under the condition of outdoor pond,and fed with compound feed(CF group)and chilled fish(CTF group) respectively,compared the edible tissue edible rate,nutrients,edible tissue fatty acids and free amino acids of Chinese mitten crab.The experiment showed that:(1)After fattening,the hepatopancreas index of crabs in both female and male CF group was higher than that of CTF group,while the gonadal index was lower than that of CTF group,and there was no significant difference in meat yield,total edible rate and fatness(P>0.05);(2)The fat content in muscle of CF group and CTF group was significantly increased,and the protein of male Chinese mitten crab was significantly increased(P<0.05).In hepatopancreas,the fat content of crabs in the CF group was significantly higher than that in the CTF group,while the water(except male)and protein content were significantly lower than those in the CTF group(P<0.05).In gonads,the water content of female river crabs CF group and CTF group increased significantly,and the protein and fat contents decreased significantly(P<0.05),while the protein content of male Chinese Mitten Crab CTF group was significantly higher than that of CF group,while the fat content was significantly lower than that of CF group(P<0.05);(3)The contents of C18:2n6(LA)and C18:3n3(LNA)in edible tissues of CF group were significantly higher than those of CTF,while C20:4n6(ARA),C20:5n3(EPA)and C20:4n6(ARA),C20:5n3(EPA)and C20:The content of 6n3(DHA)was significantly higher than that in the CF group,and there was no significant difference in the content of EPA and DHA in muscle and testis.After fattening,the content of∑n-3PUFA in CF group remained unchanged,the content of∑n-6PUFA increased,and the ratio of n-3/n-6PUFA decreased,while the content of∑n-3PUFA in edible tissue of CTF group increased,and the content of∑n-6PUFA decreased by n-3/n-6PUFA ratio increased;(4)Regardless of the CF group or the CTF group,the levels of taurine(Thu),glutamic acid(Glu),glycine(Gly),alanine(Ala),arginine(Ary),and proline(Pro)and total amino acid(TAA),while histidine(His)decreased;taurine(Thu),aspartic acid(Asp),glutamic acid(Glu)increased in ovary,phenylalanine The content of acid(Phe)and histidine(His)decreased;the content of taurine(Thu),aspartic acid(Asp),serine(Ser),and alanine(Ala)increased in testis,tyrosine(Lys))and phenylalanine(Phe)levels decreased.The content of Glu in muscle of CTF group was significantly higher than that of CF group,and the content of Gly in CF group was significantly higher than that of CTF group;the content of Ala in ovary of CF group was significantly higher than that of CTF group,and the content of Ary in ovary of CTF group was higher than that of CF group(P<0.05).To sum up,both compound feed and chilled fish can significantly improve the nutritional quality of crabs,and chilled fish can promote the growth of gonads.In terms of fatty acids,the content of linoleic acid and linolenic acid in the edible tissues of crabs that were fed with compound feed is higher,while the hepatopancreas of the crabs fed with chilled fish has higher EPA and DHA content;In terms of amino acids,the content of sweet amino acids and umami amino acids in the muscle and gonads of compound feed crabs was significantly higher than that of chilled fish crabs.3.Comparison of nutritional quality of river crabs with compound feed and chilled fish during hoardingIn this experiment,the proportion of edible tissues,nutrient contents,fatty acids and free amino acids in edible tissues of the crab cultured with compound feed(CF group)and the crab cultured with chilled fish(CTF group)were compared in the outdoor cage.The results showed that :(1)the hepatopancreas index(HSI)of both CF and CTF groups showed a decreasing trend,while the gonad index showed an increasing trend.After stockpiling,the HSI of female and male crabs was about 4% and6%,respectively.There was no significant change in meat production rate,but the overall edible rate showed a decreasing trend.(2)In muscle,protein and fat contents in CF group and CTF group decreased first and then increased,while moisture and ash content had no significant change;In hepatopancreas,the water and protein contents of both CF and CTF grounds,while the fat content showed a decreasing trend,while the ash content had no significant change.The fat content in CTF group was higher than that in CF group.Among gonads,water content in female ovary increased slightly,but fat content showed a downward trend,while protein and ash content showed no significant change(P > 0.05).Moisture and fat content in testis of male decreased,but protein and ash content showed no significant change(P > 0.05).After stocking,the fat content in CF group was significantly higher than that in CTF group(P < 0.05).(3)The content of C18:2N6(LA)in edible tissues(except ovary)of CF group was significantly higher than that of CTF group,while the content of EPA and DHA in hepatopancreas and ovaries was significantly lower than that of CTF group(P < 0.05).After stocking,the contents of LA and C20:4N6(ARA)in edible tissues of CF group increased,while the content of LA in edible tissues of CTF group decreased.ARA had no significant change.In CF group and CTF group,the content of EPA and DHA in female muscle increased,but that in male muscle increased.Hepatopancreas EPA content increased,CTF group increased DHA content;The contents of EPA and DHA increased in CTF group,but decreased in CF group,and decreased in testis.(4)After stockpiling,the contents of taurine(Thu),glycine(Gly)and alanine(Ala)increased,while the contents of aspartic acid(Asp),threonine(Thr),arginine(Ary)and proline(Pro)decreased.The contents of Gly and Ary and Pro were significantly decreased in male muscle.The content of aspartic acid(Asp)in female ovary increased,while the contents of taurine(Thu),arginine(Ary),proline(Pro)and total amino acid(TAA)decreased.The contents of glycine(Gly)and proline(Pro)in male testis increased,while the contents of taurine(Thu)decreased.To sum up,during the hoarding stage,the HSI index of the two kinds of bait crabs decreased and the GSI index showed and upward trend,Although there is no obvious"gloss loss"phenomenon,there is a significant loss of nutrients in edible tissues,especially in the hepatopancreas.From the perspective of fatty acids and free amino acids,hoarding can optimize the fatty acids of crabs,and the sweetness in the muscles The amino acid content increased,while the umami and sweet amino acids decreased in the gonads,especially the ovaries. |
