| Chinese mitten crab(Eriocheir sinensis)is an important and unique freshwater economic animal in China.It is deeply favorable by consumers as its rich nutrition and delicious taste.Hubei is located in the middle reaches of the Yangtze River with a long history of raising E.sinensis.However,the basic information related to growing law,nutrition demands and fattening techniques of raising E.sinensis is still not insufficient.The feeding of E.sinensis is still mostly by natural feedstuffs such as soybean meal,maize and chilled fish,facing the difficult situation of standardizing feeding techniques;Meanwhile,the quality of commercial feedstuffs to E.sinensis is varied,which has not been wide-scale used yet.In order to discuss the influences of the tuo kinds of feed as natural bait and compound feed on the aspects of E.sinensis including the growth and physiology,muscle tissue characteristics and nutrient composition of during fattening period,this paper takes the E.sinensis with fattening period from May to October as the experimental subjects,and respectively uses tuo kinds of feed as natural bait(soybean meal: maize: wheat: seafood chilled fish = 2:3:2:1,crude protein: crude fat = 5:1)and compound feed(crude protein: crude fat = 5:1)in two adjacent separated ponds for raising experiment.And then carry out the comparisons between their growth law,antioxidant capability,muscle structure and nutrient composition.The following results of study are obtained:1.Differences in growth,development and antioxidant capacity of E.sinensis under two kinds of feeding conditionsThe average body weight of males in natural diet group was lower in the early stage,but the weight gain rate was higher in the later stage,and the average body weight in mature stage in October was significantly higher than that in compound diet group(P<0.05).The gonad development of females in natural diet group was late,and the gonad index(GSI)at maturity in October was significantly higher than that in compound diet group.The gonad development of females in the natural diet group was also late,but the gonad development rate was faster.There was no difference in GSI at maturity between the natural diet group and the compound diet group.The activities of total superoxide dismutase(T-SOD),catalase(CAT),alanine aminotransferase(ALT)and malondialdehyde(MDA)contents in males and females fed on natural diet group were significantly higher than those in compound diet group(P<0.05),and CAT activities and MDA contents decreased to no difference in late culture period.The activity of T-SOD and ALT decreased to lower than that of the compound feed group at the maturity stage in October.The results of this study showed that the compound diet of E.sinensis had high early weight gain rate,early gonad development,low serum antioxidant level and little oxidative damage during culture.When fed with natural food,the weight gain rate of E.sinensis in the later stage is higher,the gonad development is late,the gonad coefficient of females in mature stage is higher,the activity of antioxidant enzymes in serum is higher,and the organism has stronger resistance to disease.2.Differences in muscle tissue characteristics of E.sinensiss under two kinds of feeding conditionsThe muscle fiber diameter of male and female E.sinensiss in natural diet group was significantly lower in August than that in compound diet group,and significantly higher in maturity stage in October than that in compound diet group(P<0.05).In the experimental groups of August and September abdominal muscles of females,and September abdominal muscles and foot muscles of males,the muscle microfiber index in the natural diet group was significantly lower than that in the natural diet group(P<0.05),but no significant difference between the tuo kinds of feed was found in various muscles in the mature stage of October.During the experiment,there was no significant difference in total collagen content,hot melt collagen content and thermal residual collagen content between the tuo kinds of feed.According to the evaluation results of the muscle tissue characteristics evaluation model,the muscle tenderness of the compound diet group was better than that of the natural diet group in September and October.3.Differences in nutritional composition of E.sinensis under two kinds of feeding methodEther extract content in male hepatopancreas from August to October in the compound diet group was higher than that in natural diet group,and ether extract content in female hepatopancreas in natural diet group was significantly higher than that in natural diet group in October(P<0.05).The total amino acid content(TAA)of natural diet group in August was significantly higher than that of compound diet group(P<0.05),and the essential amino acid content(EAA)of natural diet group in August and October was significantly higher than that of compound diet group(P<0.05).In muscle tissue of females,TAA in natural diet group in August and October was significantly higher than that in compound diet group(P<0.05),and EAA in natural diet group in August was significantly higher than that in compound diet group(P<0.05).The ratio of essential amino acid(NAA/TAA)to total amino acid(NAA/TAA)ranged from 0.29～0.32 in males and 0.32～0.35 in females.Results of fatty acid in muscle tissue,the content of n-3 unsaturated fatty acid in natural diet group was significantly higher than that in compound diet group in August(P<0.05),and n-3/n-6 in natural diet group was significantly higher than that in compound diet group in the same period(P<0.05).The content of eicosapentaenoic acid(EPA)in natural diet group was significantly higher than that in compound diet group in August and September(P<0.05),and the ratio of eicosapentaenoic acid to docosahexaenoic acid(EPA/DHA)was lower than that in compound diet group.n-3/n-6in natural diet group was significantly higher than that in compound diet group(P<0.05),which was consistent with the experimental results of males.In hepatopancreas tissue fatty acid results,the content of n-3 unsaturated fatty acid in male natural diet group was significantly higher than that in the compound diet group in August(P<0.05),n-3/n-6was significantly higher than that in the compound diet group in August and September(P<0.05),and EPA content in male natural diet group was significantly higher than that in the compound diet group in August and September(P<0.05).EPA/DHA was lower than that of the compound feed group.The content of n-6 unsaturated fatty acids in natural diet group was significantly lower than that in compound diet group in August and September(P<0.05),and the n-3/n-6 content in natural diet group was also significantly higher than that in compound diet group in the same period(P<0.05).EPA/DHA in natural diet group was significantly lower than that in compound diet group(P<0.05).In the gonad fatty acid results,DHA in natural diet group was significantly higher than that in compound diet group(P<0.05),and C18:1 in natural diet group was significantly lower than that in compound diet group(P<0.05).The saturated fatty acids(SFA)and polyunsaturated fatty acids(PUFA)in natural diet group were significantly higher than those in compound diet group(P<0.05).In summary,in the later stages of raising,the E.sinensis fed with natural bait have higher weight gain rates,higher gonadal indices,higher content of muscle TAA,EAA and n-3/n-6,higher DHA content in male gonads and higher PUFA content in female gonads.While,the E.sinensis fed with compound feed have a lower antioxidant level in serum,higher muscle tissue characteristics,higher crude fat content in the hepatopancreas and higher EPA/DHA in the muscle and hepatopancreas.In this paper,tuo kinds of feed both present some advantages for the quality of E.sinensis.The natural bait is mainly beneficial for the weight gain and n-3/n-6 fatty acid ratios in the later stage of raising,and the compound feed is mainly beneficial for the muscle tissue characteristics and EPA/DHA fatty acid ratios. |
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