| Oriental river prawn(Macrobrachium nipponense)is an important traditional aquaculture species in China and other Asian countries.The aquaculture sector,which includes this vital species,is expected to play its role to overcome the challenges in food security the world might face shortly.However,recently the costs of conventional protein fishmeal have risen significantly.Thus,looking for alternative protein sources that are sustainable and do not compromise aquatic organism’s growth and other parameters is crucial.Soybean meal due to its high protein content is considered as one of the best options,but its high anti-nutritional factors are believed to influence its utilization by fish and crustaceans.Nowadays,additives like organic acid are substituting the role of antibiotics as a feed supplementation in aquafeeds,and they are used to fight diseases outbreak and to improve growth performance.Tributyrin a butyrate derivative,which can alleviate the impact from plant-based protein sources in aquaculture,had a higher utilization efficiency in the intestine.Hence,this study is aimed at investigating the effects of dietary tributyrin on the growth performance,enzymatic activities,antioxidants capacity,immune-related gene expression,and resistance against Vibrio cholera on M.nipponense.To carry out this study,six isonitrogenous(40% crude protein)and isolipidic(9% crude lipid)diets were formulated by available conventional feed ingredients,which are composed of fish meal and soya bean meal as the main protein source,based on the nutritional requirement of M.nipponense.The positive control was formulated with 30% fish meal and the negative control with 25% fish meal content,then tributyrin was supplemented at 0.05%,0.1,0.2%,and 0.4% in the negative control.Then,fifty juvenile prawns per tank were randomly distributed in the 18 tanks,and the diets were assigned randomly to six groups in triplicates,fed for a period of 56 days.The effects of dietary tributyrin in partially replaced fish meal diet on growth performance and enzymatic activities of oriental river prawn(Macrobrachium nipponense)After 56 days of the feeding trial,growth performance and feed utilization indices including,final body weight(FBW),weight gain rate(WGR),specific growth rate(SGR),survival rate(SR),condition factor(CF),feed intake(FI),protein efficiency ratio(PER)and feed convection ratio(FCR)were not significantly(P>0.05)affected by reducing fish meal content from 30% to 25% and supplementation of tributyrin in the negative control.However,the lowest growth performance was recorded in the negative control compared to the diets supplemented with tributyrin.Concerning intestinal enzymatic activity of oriental river prawn,lipase was triggered by dietary tributyrin,whereas amylase remained unaffected at all.Lipase activities significantly(P<0.05)rose as dietary tributyrin levels increased up to 0.2% and remained plateau up to the concentration of 0.4%.The effects of dietary tributyrin in partially replaced fish meal diet on antioxidant enzymatic capacity of oriental river prawn(Macrobrachium nipponense)The dietary of tributyrin affected mostly the hemolymph and hepatic antioxidant enzymatic activities.In hemolymph,malondialdehyde(MDA)was significantly(P<0.05)lowered,whereas significant increment was achieved in superoxide dismutase(SOD)and total antioxidant capacity(T-AOC),but the activities of catalase(CAT)were not affected at all.In hepatopancreas,the activities of MDA were also significantly(P<0.05)lowered,while SOD increased with increasing the concentration of tributyrin and the activities of Nitrous oxide(NO)remained unaffected.Overall,most of the antioxidants were significantly(P<0.05)impacted and showed a directly proportional relationship in hemolymph and hepatopancreas,therefore,through this investigation we can conclude that dietary tributyrin can reduce stressinduced by a partially replaced fish meal diet in oriental river prawn.The effects of dietary tributyrin in partially replaced fish meal diet on immune-related gene expression and disease resistance of oriental river prawn(Macrobrachium nipponense)against Vibrio choleraRegarding the immune-related genes,as the relative m RNA expressions of heat shock protein 70(HSP70)and Toll-like receptors(TLRs)improved significantly(P<0.05),the expression of immune deficiency(IMD),Relish and Dorsal were not influenced at all.The relative m RNA expression level of HSP70 in the groups fed with diets TB2,TB3,and TB4 were significantly(P<0.05)higher than those fed with positive control and TB4,but the group fed with negative control was not significantly(P>0.05)different from all the treatment groups.In the case of TLRs it was significantly highest(P<0.05)in the group fed TB2,but with no marked difference(P>0.05)with treatment group TB3.In the bacterial challenge test,resistance against V.cholera was significantly(P<0.05)enhanced in the groups fed diets supplemented with tributyrin and the estimated optimum tributyrin requirement was 0.26%,based on the second-degree polynomial regression analysis.Generally,this study demonstrated that feeding M.nipponense with 25% and 30% fish meal content doesn’t have any marked difference ingrowth performance.However,from the results of the antioxidant capacity,immune-related gene expression,and disease resistance,we concluded that tributyrin could be used as a potential immunostimulant for oriental river prawns. |
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