Effects of dietary cottonseed meal protein hydrolysate on growth,antioxidants and immunity of Chinese mitten crab Eriocheir Sinensis

One hundred and sixty crabs(average initial weight:51.32±0.08 g)were fed with four experimental diets containing cottonseed meal protein hydrolysate(CPH)at 0%(CPH0,control),0.3%(CPH0.3),0.6%(CPH0.6),and 1.2%CPH(CPH1.2).The experiment results show that no difference was observed in specific growth rate and survival rate of crabs fed with CPH diet.Moisture content of crabs fed with CPH0.6 diet was significantly reduced than that of the CPH0 group.Superoxide dismutase and catalase activities of crabs fed with CPH0.6 diet were significantly increased and the difference was not significant between the CPH0.3 and CPH0.6 groups.Malondialdehyde content of CPH0.3 group was significantly lower than that of the CPH0 group.Lysozyme,alkaline phosphatase,and acid phosphatase activities of CPH0.3 diet crabs were significantly higher than that of the CPH0 group.Glutamic-pyruvic transaminase activity of crabs fed with CPH0.3 diet was significantly decreased compared to the CPH0 group.The relative expression levels of Toll1,Toll2,MyD88,LITAF,and ILF-2 of crabs fed with CPH0.3 diet were significantly higher than that of the CPH0 group.The expression level of SOCS2 showed an opposite pattern.After CPH perfusion,the expression levels of SOCS2 and Toll1 in intestine at time 3 h and SOCS2 in hepatopancreas at time 18 h increased significantly to the highest value.The expression level of Toll2,MyD88,LITAF,decreased at times 6 h,6 h,12 h,respectively,then increased gradually.Therefore,supplementation of dietary CPH could improve antioxidant capacity and immune function;the appropriate supplement dosage of CPH for crab could be 0.3%-0.6%.Furthermore,the short-term CPH stimulation could significantly increase or decline the expression levels of immune-related genes at different times after CPH perfusion.

Aquafeed fermentation improves dietary nutritional quality and benefits feeding behavior,meat flavor,and intestinal microbiota of Chinese mitten crab(Eriocheir sinensis)

Normally,proper fermentation can be an efficient and widely used method to improve feed quality in animal rearing;however,the studies on crustaceans,especially Eriocheir sinensis,remain limited.This study aimed to investigate whether feed fermentation could meliorate dietary nutritional value and benefit E.sinensis rearing.First,non-fermented feed(NFD)and fermented feed(FD)were produced and assessed,respectively.Then,the“Y”maze feed choice behavior test(180 times;30 times,6 rounds)was conducted to assess the attractiveness of these 2 feeds for crabs.Finally,a total of 80 crabs(44.10±0.80 g)were randomly assigned into 2 groups with 4 replicates,and fed the experimental diets for 8 weeks to evaluate the effects of each feed on growth,antioxidant capacity,meat flavor,and intestinal microbiota.In this study,FD showed higher levels of crude protein(P<0.01),soluble protein(P<0.01),amino acids(P<0.05),lactic acid(P<0.001),and lower levels of crude fiber(P<0.05)and antinutritional factors(agglutinin,trypsin inhibitor,glycinin,andβ-conglycinin)(P<0.001)than NFD.Additionally,FD was more attractive to crabs than NFD(P<0.01)and it stimulated the appetite of crabs more than NFD(P<0.05).The growth performance,feed efficiency,and digestive enzyme activity of FDfed crabs were significantly higher than those of NFD-fed crabs(P<0.05).The electronic sensory measurements and free amino acid profiles revealed that the FD diet had positive impacts on the meat flavor of crabs,particularly in“sweet”and“umami”tastes.Moreover,the antioxidant capacity of FD-fed crabs was significantly higher than that of NFD-fed crabs(P<0.05).Fermented feed also affected the diversity and composition of intestinal microflora.The functional prediction of microbial communities showed that crabs fed FD had a better microecological environment in the intestine.In conclusion,the fermentation of aquafeed could be an effective approach to enhance feed quality and therefore benefit E.sinensis rearing.