| The sustainable development of aquaculture was influenced by the fish meal which was limited and expensive.For reducing the reliance on fish meal,it is necessary to explore some viable alternative dietary protein sources so as to save the use of fish meal in diets.Krill meal,which has an abundant potential reserves,is a high-quality protein source with balance of amino acids.In fish or shrimps,it has been investigated that dietray krill meal could improve the growth performance and decrease the feed conversion ratio.In this research,some feeding trials have been conducted to study the effect of krill meal on growth performance,protein metabolism and antioxidant capacity of juvenile Chinese mitten crabs,Eriocheir sinensis by supplementated in a low fishmeal diet or as a substitute for fishmeal.This study could provide some guidance for the rational use of krill meal in diets of juvenile Chinese mitten crab in the future.The main results and conclusions of this study are as follows:1 Effects of krill meal on growth performance,digestive enzyme activity and amino acids retention of juvenile Chinese mitten crab,Eriocheir sinensisA feeding trial was conducted to develop a low fish meal practical diet for juvenile Chinese mitten crab,Eriocheir sinensis by supplementing krill meal.Five isonitrogenous(42% crude protein)and isolipidic(9% crude lipid)test diets were formulated,which the diet contained 35% fish meal(FM)was a FM-based control diet(F35),and the rest diets were prepared by replacing different level of FM protein with soybean meal and cottonseed meal as follows: a 20% FM-containing diet(F20),a 15% FM-containing diet(F15),20% FM-containing diet supplementation with 5%(F20+),15% FM-containing diet supplementation with 5% krill meal(F15+).Five replicates for each group of juvenile crabs(average initial weight 0.22 ± 0.01 g)were randomly stocked in 20 tanks at a stocking density of 40 juvenile crabs per tank.Thejuvenile crabs were fed to satiation by hand three times daily,7 days per week for a period of 50 days.Results showed that weight gain(%),specific growth rate(SGR),total essential amino acids retention and protein retention were all significantly(P <0.05)decreased in juvenile crabs fed F20 diet compared to F35 diet,while there were no significant(P > 0.05)difference in feed efficiency ratio,protein efficiency ratio and activities of trypsin between F20 and F35 diet;All those parameters mentioned above significantly(P < 0.05)decreased in juvenile crabs fed F15 diet than F35 diet(P < 0.05).However,feed efficiency ratio,protein efficiency ratio and trypsin activity were significantly(P < 0.05)increased in juvenile crabs fed F15+ diet compared to F15 diet while no significant difference was detected on growth performance and amino acids retention.Nevertheless there was no significant alteration was identified on growth performance,feed utilization,digestive enzyme activity and amino acids retention rate of juvenile crabs fed F20+ and F20 diets.In summary,the lower growth and total essential amino acids retention rate was found in juvenile crabs fed low fishmeal diets where the protein level balanced by soybean meal and cottonseed meal.Furthermore,there was worse feed utilization than control while the fish meal level of diet was decreased to 15%,however,the supplementation of 5% krill meal had positive effects on the digestion and absorption of protein and feed utilization.Therefore,it is recommended that krill meal could be supplemented in a low fishmeal diet in order to improve feed utilization.2 The effect of different levels of krill meal supplementation of low fishmeal diets on growth performance,protein metabolism and antioxidant capacity of juvenile Chinese mitten crabs,Eriocheir sinensisIn this study,the feasibility of low fishmeal diets for juvenile crabs was investigated by using low fishmeal diets containing various proportions of krill meal.Six isonitrogenous(40% crude protein)and isolipidic(8% crude lipid)test diets were prepared,where the positive control diet(35% FM,F35)and the negative control diet(15% FM,F15)without krill meal and 15% FM diets were supplemented with 5,10,15,20% krill meal,respectively(K5,K10,K15,K20,respectively).Five replicates for each group of juvenile crabs(average initial weight 2.63 ± 0.07 g)were randomly stocked in 30 tanks at a stocking density of 35 juvenile crabs per tank.The juvenile crabs were fed to satiation by hand three times daily,7 days per week for a period of56 days.At the end of the feeding trial,compared to the positive control F35 group,the growth and antioxidant capacity were not influenced(P>0.05)by the decreasing of fish meal,but the feed efficiency ratio,protein efficiency ratio,protein retention rate,the activities of trypsin and glutamic pyruvic transaminase(GPT)in hepatopancreas,the expresstion of mechanistic target of rapamycin(mTOR),ribosomal protein S6 kinase 1(S6K1)and ribosomal protein S6(S6)were significantly(P < 0.05)lower in juvenile crabs fed F15 diet.The highest weight gain and specific growth rate were found in juvenile crabs fed K20 diet,followed by K15 group.No significantly(P > 0.05)difference on growth was observed between K15 and K20 groups,but those groups grew significantly(P < 0.05)faster than F15.There was no significant(P > 0.05)difference on the feed efficiency ratio,protein efficiency ratio and protein retention rate among K5、K10 and K15 groups,and those groups were all significantly(P < 0.05)higher than F15 group and furthermore lower than K20 diet(P < 0.05).The activities of trypsin in hepatopancreas were significantly(P < 0.05)better in juvenile crabs fed those diets supplementated with krill meal compared to F15 diet.And the activities of glutamic pyruvic transaminase(GPT)was significantly(P < 0.05)higher in juvenile crabs fed K10,K15 and K20 diets than F15 diet.The expression of mechanistic target of rapamycin(mTOR),ribosomal protein S6 kinase 1(S6K1)and ribosomal protein S6(S6)were significantly(P < 0.05)increased in hepatopancreas of juvenile crabs fed K20 diet compared to F15 diet,while no significant difference(P > 0.05)was found between the rest of krill meal diets and F15 diet.GOT and GPT in serum were not influenced(P > 0.05)by the dietarytreatments.The contents of malondialdehyde(MDA)and the activities of superoxide dismutase(SOD)were significantly(P < 0.05)reduced in hepatopancreas of juvenile crabs fed K20 diet compared to F15 diet,and the total antioxidant capacity(T-AOC)were significantly(P < 0.05)stronger in hepatopancreas of juvenile crabs fed K20 diet compared to F15 diet,while no significant(P > 0.05)alteration was identified on the contents of MDA and antioxidant capacity of juvenile crabs fed the other diets containing krill meal compared to F15 diet.In addition,no significant difference(P >0.05)was observed on growth,feed efficiency ratio,protein efficiency ratio,protein retention rate and the activities of digestive enzymes of juvenile crabs between K5 and F35 groups.And there was significantly better growth(P < 0.05),feed utilization(P < 0.01)and T-AOC in juvenile crabs fed K20 diet compared to F35 diet except for the activities of SOD,which was significantly decreased(P < 0.05).Based on the present experimental condition,it can be concluded that krill meal had positive effects on growth performance,feed utilization and antioxidant capacity of juvenile crabs with the increasing levels of dietary krill meal.Therefore,it is recommended to supply 5% krill meal in practical produce to avoid the bad efficiency of a low fishmeal diet and to have an equal effect with fish meal diet,or supply 20% krill meal in order to acquire faster growth,higher feed utilization and better antioxidant capacity compared to fish meal.3 Effects of replacement of dietary fishmeal by Antarctic krill meal on growth performance,protein metabolism and antioxidant capacity of juvenile Chinese mitten crab,Eriocheir sinensisThe purpose of this study was to evaluate the potential of krill meal as a substitute for fishmeal by investigating the growth performance,protein metabolism and antioxidant capacity of juvenile Chinese mitten crab(Eriocheir sinensis).Five isonitrogenous(39% crude protein)and isolipidic(8% crude lipid)test diets were formulated by replacing 0(R0),25(R25),50(R50),75(R75)and 100%(R100)ofthe fishmeal protein with krill meal.Five replicates for each group of juvenile crabs(average initial weight 0.52 ±0.02 g)were randomly stocked in 25 tanks at a stocking density of 40 juvenile crabs per tank.The juvenile crabs were fed to satiation by hand three times daily,7 days per week for a period of 56 days.Results showed that the weight gain,specific growth rate and molting rate were significantly(P < 0.05)higher in juvenile crabs fed R50,R75 and R100 diets compared to R0 diet.The fastest growth and molting rate were observed in juvenile crabs fed R100 diet,followed by R75 diet,whose values were not significantly(P > 0.05)different from each other.The feed efficiency ratio,protein efficiency ratio,protein retention and total essential amino acids retention of the R50,R75,and R100 groups were significantly(P < 0.05)increased in juvenile crabs fed R50,R75 and R100 diets compared to R0 diet.(P <0.05).The feed utilization in diet R100 was the highest among dietary treatments.There were no significant(P > 0.05)difference in growth,molting and feed utilization of juvenile crabs fed R25 and R100 diets except for protein efficiency,which was significantly(P < 0.05)increased in juvenile crabs fed R25 diet.The feed supplemented with krill meal could improve the molting synchronism of the juvenile crabs.The ratio of essential amino acid to total amino acids in the dry matter of juvenile crabs was positively correlated with dietary profiles and the level of dietary krill meal.The expression level of mechanistic target of rapamycin(mTOR),ribosomal protein S6 kinase 1(S6K1),ribosomal protein S6(S6)and eukaryotic translation initiation factor 4E(eIF4E)genes related to m TOR signaling pathway of hepatopancreas in juvenile crabs were not significantly(P > 0.05)different in all krill-containing diets.Compared to R0 diet,a increased expression of mTOR and a reduced expression of 4E-BP1 were observed in juvenile crabs fed krill-containing diets,while no difference was detected about the expression of eIF4 E between R0 and all krill-containing diets.The expression of S6K1 in R50,R75 and R100 groups and S6 in R75 group were significantly(P < 0.05)higher than those in R0 group.Theactivities of trypsin and glutamic pyruvic transaminase were significantly(P < 0.05)better in juvenile crabs fed R75 and R100 diets than those fed R0 diet(P < 0.05).The total antioxidant capacity was significantly(P < 0.05)higher of hepatopancreas in juvenile crabs fed R50、R75 and R100 diets compared to R0 diet(P < 0.05),the content of malondialdehyde(MDA)and the activity of superoxide dismutase were significantly(P < 0.05)lower than those in R0 group(P < 0.05).Summarizing the above results,a high proportion of krill meal in place of fish meal promoted the digestion、absorption and syntheses of protein,molting,the growth performance,feed utilization,reduced the degree of lipid peroxidation and improved the total antioxidant capacity.Based on the present experimental condition and culture cycle,there was no any adverse effects on growth at a high proportion or even complete replacement of fish meal with krill meal.It is suggested that krill meal could be as a viable alternative dietary protein source for fishmeal of juvenile crabs. |
PDF Full Text Request