Effects Of Fish Protein Hydrolysates On Growth Performance And Taurine Metabolism In Juvenile Turbot (Scophthalmus Maximus L.) Fed Diets With High Levels Of Plant Protein

Turbot (Scophthalmus maximus L.), an important marine carnivorous fish inChina, was widely farmed. This study was conducted to investigate the effects of fishprotein hydrolysates on growth performance of fish fed diets containing higher plantprotein level and clarify the mechanism of the fish growth promoting effects ofprotein hydrolysates. The results are summarized as follows:1. The effects of fish protein hydrolysates on the growth and digestibility ofjuvenile turbot (Scophthalmus maximus L.)A68day feeding experiment was conducted to investigate the digestion ofjuvenile turbot (initial weight16.05±0.03g) fed plant-protein diets with differentmolecular weight fish protein hydrolysate. Five diets were formulated to be isolipidic,isonitrogenous and isoenergetic. Diets UF10(ultrafiltered fish protein hydrolysate),FPH10(fish protein hydrolysate) and RF10(retentate fish protein hydrolysate)contained5.4%,5.5%and5.5%of protein hydrolysates (10%of total dietary protein),respectively. Diet PP contained no protein hydrolysate. Diets UF10, FPH10, RF10andPP contained18%of fish meal. The control group included fish meal as the singleprotein source. The results indicated that special growth ratio was not significantlydifferenct in UF10, FPH10and PP groups compared with that of fish fed diet FM(P>0.05). There were no significant differences in feed efficiency (FE), proteinefficiency ratio (PER) and protein productive value (PPV) between fish fed diet UFand diet FM (P>0.05). Fish fed diets FPH10, RF10and PP had significantly lower FE,PER and PPV than that of fish fed diet FM (P<0.05). Apparent digestibilitycoefficients (ADC) of dry matter and protein in UF10, FPH10and RF10groups weresignificantly higher than that of PP group (P<0.05), while were significantly lower than that of FM group (P<0.05). Fish fed diet UF10had significantly higher ADC ofdry matter and protein compared with that of FPH and RF10groups (P<0.05). ADCof16amino acids and taurine was significantly affected by dietary treatments(P<0.05). ACD of most amino acids was the highest in FM group and the lowest inPP group among all groups. An opposite tendency of apparent digestibility coefficienthas been found in cysteine and taurine between diets contain protein hydrolysates(UF10, FPH10and RF10) and other diets (FM and PP). In conclusion, there was anincreasing trend in growth and feed utilization when juvenile turbot was fed highplant protein diets contained UF and FPH, andACD of dry matter, protein and aminoacids could be improved in FPH and UF10groups. The low molecular weight UF hada better effect on the growth than that of FPH and RF. ACD of taurine seemed todecrease in fish given plant-protein diets inclusion fish protein hydrolysate.2. Ultrafiltered fish protein hydrolysate had high digestibility but low utilizationof dietary protein for growth in juvenile turbot (Scophthalmus maximus L.)given high plant protein dietsThis study was conducted to investigate the effect of ultrafiltered fish proteinhydrolysate (UF) inclusion levels on growth, feed utilization and apparentdigestibility coefficients (ACD) for juvenile turbot (Scophthalmus maximus L.) fedplant-protein diets. Fish hydrolysate was produced by enzymatic treatment andpermeate fraction was obtained as UF by ultrafiltered step. Experimental diets (UF-0,UF-5, UF-10, UF-15and UF-20) were prepared containing68%of plant protein andfish meal protein was respectively replaced by0%,5%,10%,15%and20%UF ofdietary protein. Diet PP contained about78%of plant protein and diet CAA containedabout10%of crystalline amino acid mixture. All diets were fed to7triplicate groupsof turbot (initial weight16.05±0.03g) for68days. Results indicated that feed intakeamong all groups was not significantly different (P>0.05). Fish fed diets UF0andUF20shown significantly higher specific growth rate (SGR) compared with that infish fed diet UF20(P<0.05), while SGR in UF0, UF5, UF10, UF15, PP and CAA10groups was not significantly different(P>0.05). Feed efficiency was the highest in UF0group and the lowest in UF20group. Fish fed diet UF0was significantly higherprotein efficiency ratio than that in fish fed diets UF20, PP and CAA10. Fish in UF0,UF5and UF10groups was significantly higher protein productive value (PPV) thanthat in fish given UF20. Fish fed diets contained low level UF had higher digestibility(dry matter, protein and amino acids) than that diets UF-0, PP and CAA. It indicatedthat low level UF had high digestibility and improved low utilization of feed forgrowth in turbot given plant-protein diets. Fish fed diet UF-10had an increasingtendency in growth and feed utilization compared with other diets contained UF. Inaddition, high level free amino acids may be a main reason for reduced growth of fishfed diets included high level UF.3. NMR spectroscopy based metabolomic analysis of liver and muscle fromturbot (Scophthalmus maximus L.) given plant-protein diets contained levelsand molecular weight protein hydrolysatesThe aim of the study was to assess metabolites in liver and muscle from juvenileturbot fed diets contained different levels and molecular weight protein hydrolysates.A Nuclear Magnetic Resonance (NMR) based metabolic profiling approach was usedto profile metabolite changes in liver and muscle of juvenile turbot (Scophthalmusmaximus L.). The results indicated that40metabolites were identified in liver usingNMR-based metabolomics. Metabolites involved in amino acid biosynthesis,carbohydate metabolism, TCA cycle, taurine biosynthesis, methyl metabolism,betaine biosynthesis and respiratory chain metabolism. Besides, these metabolitesalso included some organic acids and amine. There were37metabolites identified inmuscle and they contained the same metabolism excepted for hydroxyprolinemetabolism but some metabolites were different. In conclusion, according toassessment of metabolites, glutamine may show significant changes in liver fromfish fed different molecular weight protein hydrolysates. Cholate, leucine, valine,isoleucine, alanine, arginine and aspartate may also show significant changes in liveramong high level UF groups. Meanwhile, histidine may show significant changes inliver from fish fed diets contained different molecular weight protein hydrolysates. Proline, glutamate, glutamine, asparagine, cystathionine, fumarate, tyrosine may alsoshow significant changes in muscle among high level UF groups. Besides, cholate,leucine, valine, isoleucine and arginine of liver and glutamine of muscle may showsignificant changes in fish given different molecular weight protein hydrolysates.4. The effects of ultrafiltered fish protein hydrolysate and taurine on growth,taurine metabolism and intestinal morphology of juvenile turbot(Scophthalmus maximus L.)An84-day growth trail was conducted to investigate the effects of ultrafilteredfish protein hydrolysate and taurine on growth, taurine metabolism and intestinalmorphology of juvenile turbot (Scophthalmus maximus L.). Diets FM, UF0, UF0+T,UF10and UF10+T contained30%,15%,15%,8%,8%fish meal, sepatately. Inaddition, diets UF10and UF10+T included10%ultrafiltered fish protein hydrolysatein dietary protein and diets UF0+T and UF10+T were added0.8%taurine. The resultsindicated that there was no significantly lower in growth and feed utilization in UF10(UF10+T) group than that in UF0(UF0+T) group (P>0.05). Cysteamine dioxygenase(CDO) activities and taurine content of tissues in fish given diets (UF0+T andUF10+T) contained taurine had significantly higher than fish fed diets FM, UF0andUF10(P<0.05). Ultrafiltered fish protein hydrolysate had no significantly effect onforegut and midgut morphology, and taurine increased intestinal microvillus height,enterocyte height and the number of fold. In conclusion, low level ultrafiltered fishprotein hydrolysate could play the similar role with fish meal in growth and feedutilization for juvenile turbot. And taurine were also essential nutrition for turbot fedplant-protein diets contained ultrafiltered fish protein hydrolysate.