| The study was conducted to evaluate the potential and limitation of terrestrial animal and plant protein in the diet,and investigate the regulation of proteometabolism and food intake of Chinese soft-shelled turtle Pelodiscus sinensis.Based on these studies,we developed a new protein source with several different types of protein sources and functional additives blended to replace the dietary fish meal as much as possible.The present study mainly included six parts presented as follows:1 Effects of fish meal replacement with meat and bone meal and expanding blood meal on growth performance,nutrient digestibility and body composition of juvenile Chinese soft-shelled turtle Pelodiscus sinensisAn 8-week feeding trial was conducted to evaluate the potential of partial replacement of fish meal with rendered animal protein blend(APB)(meat and bone meal:expanding blood meal=4:1)in the diet of juvenile Chinese soft-shelled turtle Pelodiscus sinensis.Seven isonitrogenous and isoenergetic practical diets replacing 0,10,20,30,40,50 and 60%fish meal protein by APB were formulated.Weight gain,feed efficiency,protein efficiency and the apparent digestibility coefficients(ADCs)of dry matter and gross energy in the experimental diets all exhibited no significant difference(P>0.05)when dietary fish meal was replaced for 0-40%,but decreased significantly(P<0.05)with further increasing substitution levels.However,relative feed intake,ADC of lipid as well as the contents of whole-body moisture,protein,lipid and ash all showed little differences(P>0.05)among all the treatments.Nitrogen retention and the ADCs of protein and most amino acids all decreased significantly(P<0.05)when fish meal was substituted for more than 30%.The results indicated that fish meal in the practical diet of juvenile Chinese soft-shelled turtle could be replaced for 30-40%by a combination of meat and bone meal and expanding blood meal without negative effects on growth performance,nutrients digestibility and body composition.2 Different preference is modulated by the feeding stimulants supplementation in different Chinese soft-shelled turtle(Pelodiscus sinensis)basic dietsFive 2-week feeding trials were conducted to investigate five stimulants on P.sinensis.Two isonitrogenous and isoenergetic diets were formulated,one contained 60%fish meal(HFM diet),the other contained 42%fish meal and 22.5%animal protein blend(LFM diet),and each tested one stimulant with four levels.The feeding stimulant candidates were betaine,2-carboxy ethyl dimethyl sulphonium bromide(DMPT),inosine-5'-monophosphate(IMP),taurine and squid extract.In the experiment on each stimulant,turtles(10.85±0.10g)were equally divided into HFM and LFM groups and fed with an equal mixture of corresponding diets containing four levels of stimulants,respectively.Each diet contained a unique rare earth oxide as inert marker.Turtles were fed twice daily(8:00 and 17:00),and feces were collected.Preference for each diet was estimated based on the relative concentration of each marker in the feces.In HFM groups,only IMP showed the enhanced attraction.But in LFM groups,all the stimulants,except IMP,showed higher preference than basal diets for at least one inclusion level,and the optimum level was 1%for betaine,0.01%for DMPT,0.01%for IMP,0.5%for taurine and 1%for squid extract,the squid extract had the strongest stimulating effect among the stimulants.3 Effects of fish meal replacement by rice protein concentrate and its optimization on growth,digestion and metabolism of juvenile Chinese soft-shelled turtle Pelodiscus sinensisAn 8-week study was conducted to evaluate the effects of fish meal replacement by rice protein concentrate with microcapsule L-lysine and squid extract supplementation on growth,digestion and metabolism of juvenile Chinese soft-shelled turtle.Four isonitrogenous and isoenergetic(47%protein,18 MJ/kg gross energy)practical diets were formulated with the inclusion of 60%fish meal(CT),42%fish meal + 18%rice protein concentrate(RP),42%fish meal + 18%rice protein concentrate + 1.5%microcapsule L-Lys(RPL)and 42%fish meal + 18%rice protein concentrate + 1.5%microcapsuleL-Lys +1%squid extract,respectively.The turtles were cultured in the concrete tankages outdoor and feed thrice daily.The results showed that fish meal replacement by rice protein concentrate significantly decreased the growth and nutrition retention,and increased the feed coefficient(P<0.05).However,the index aforesaid showed no significant difference when Lys was supplemented(P>0.05).In addition,growth performance,feed efficiency and relative feed intake increased significantly with squid extract inclusion(P<0.05).As to hepatic metabolic enzymes,compared with CT group,RP group showed significant decreased activities of alanine aminotransferase(GPT)and xanthine oxidase(XOD),RPL group showed significant decreased activity of GPT,and RPS group showed significant increased activity of GPT(P<0.05).As to intestinal digestive and absorptive enzymes,compared with CT group,RP group presented significant activities of protease and urinary brush border enzymes(P<0.05).The activities of enzymes above increased significantly with Lys supplementation,but were also lower than that in CT group(P<0.05).Besides that,the activities of carboxypeptidase A increased significantly with squid extract inclusion(P<0.05)while no significant differences were found in other digestive and absorptive enzymes(P>0.05).The results suggested that rice protein concentrate could replace 30%dietary fish meal of with microcapsule L-lysine inclusion Chinese soft-shelled turtle,and adding squid extract on this base could promote growth and feed intake markedly.4 Effects of fish meal replacement by rice protein concentrate with microcapsule L-lysine supplementation on amino acid transportation and proteometabolism of juvenile Chinese soft-shelled turtle Pelodiscus sinensisAn 8-week study was conducted to evaluate the effects of amino acid imbalance to amino acid transportation and proteometabolism of juvenile Chinese soft-shelled turtle.Three isonitrogenous and isoenergetic(47%protein,18 MJ/kg gross energy)practical diets were formulated with the inclusion of 60%fish meal(CT),42%fish meal+18%rice protein concentrate(RP)and 42%fish meal + 18%rice protein concentrate + 1.5%microcapsule L-Lys(RPL),respectively.The turtles were cultured in the concrete tankages outdoor and feed thrice daily.The results showed that the expression of most intestinal amino acid transporters,hepatic phosphorylated protein in mTOR pathway and muscular MuRF1 and MAFbx protein were significantly affected by diets,time and their interaction(P<0.05).As with the mRNA expression of the intestinal amino acid transporters,CT andRPL group reached the peak at 6h after feeding while RP group reached the peak at 12h after feeding(P<0.05),and decreased afterwards.The phosphorylated protein expression of Akt,mTOR,p70 S6 Kinase and 4E-BP1 followed the similar tendency to the intestinal amino acid transporters.As to the expression of muscular MuRF1 and MAFbx protein,the tendency of CT and RPL group was similar with that of protein expression in mTOR pathway while RP group showed an inverse trend to protein expression in mTOR pathway.The results suggested that Lys deficiency could postpone and decrease the postprandial expression of most intestinal amino acid transporters,hepatic phosphorylated protein in mTOR pathway.However,the effects of dietary amino acid profile on the expression of muscular MuRF1 and MAFbx were for further research.5 Effects of fish meal replacement by rice protein concentrate with squid extract supplementation on food intake regulation of juvenile Chinese soft-shelled turtle Pelodiscus sinensisAn 8-week feeding trial was conducted to evaluate the food intake regulation of rice protein concentrate with squid extract supplementation in the diets of Chinese soft-shelled turtle.Three isonitrogenous and isoenergetic practical diets were formulated with the inclusion of 60%fish meal(CT),42%fish meal + 18%rice protein concentrate + 1.5%microcapsule L-Lys(RPL)and 42%fish meal + 18%rice protein concentrate+1.5%microcapsule L-Lys +1%squid extract(RPS),respectively.Turtles were cultured in the concrete tankages and fed thrice daily to apparent satiation.Leptin receptor(LEPR),insulin receptor(INSR)and brain-gut peptides were significantly affected by the diets,time and their interaction(P<0.05).The mRNA expression of LEPR and INSR in the brain and gut significantly increased to peaks at 3h fasting(P<0.05),afterwards decreased.The expression of the anorexigenic peptides such as pro-opiomelanocortin(POMC),cocaine and amphetamine-regulated transcript(CART),cholecystokinin(CCK),cholecystokinin 1 receptor(CCK1R)and glucagon-like peptide-1 receptor(GLP-1R)presented the similar trend to that of LEPR and INSR.However,the expression of neuropeptide Y(NPY)and peptide YY(PYY)decreased markedly at 3h fasting,then increased to the peaks at 6-12h fasting(P<0.05),afterwards decreased.The results suggested that fish meal replacement by rice protein concentrate with L-Lys supplementation showed no significant difference on the expression of appetite peptides(P>0.05).Furthermore,squid extract supplementation could increase the expression of orexigenic peptides and decrease the expression of anorexigenic peptides(P<0.05).6 Effects of fish meal replacement with protein blend on growth,digestion and proteometabolism of juvenile Chinese soft-shelled turtle Pelodiscus sinensisAn 8-week study was conducted to evaluate the potential of partial replacement of fish meal with protein blend(PB)in the diet of juvenile Chinese soft-shelled turtle Pelodiscus sinensis.Three isonitrogenous and isoenergetic(48%protein,18 MJ/kg gross energy)practical diets replacing 0,30 and 50%fish meal protein by PB were formulated.The formulation of PB included rice protein concentrate,poultry by-products meal,yeast extract powder,spray-dried plasma meal,fructo-oligo saccharide,bacillus licheniformis,microcapsule L-Lys and taurine.The turtles were cultured in the concrete tankages outdoor and feed twice daily.The results showed that weight gain rate,specific growth rate and relative feed intake increased significantly when 30%dietary fish meal were replaced while only relative feed intake increased significantly with 50%fish meal replaced(P<0.05).As with the activities of intestinal digestive and absorptive enzymes,no significant difference was observed when 30%fish meal were replaced(P>0.05),but the activities of protease and amylase decreased significantly with 50%fish meal replaced(P<0.05).In addition,when PB replaced 50%fish meal,the length of intestinal villous,as well as the immunohistochemical expression of phospho-mTOR and phospho-4E-BP1 deceased significantly(P<0.05).The results suggested that PB was an outstanding feeding stimulant for Chinese soft-shelled turtle.Besides,PB could promote growth with 30%fish meal replaced,but further substitution might result in the decline of protein efficiency. |
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