Comparison of Free and Dipeptide Lysine Utilization in Diets for Juvenile Olive Flounder Paralichthys olivaceus
Comparison of Free and Dipeptide Lysine Utilization in Diets for Juvenile Olive Flounder Paralichthys olivaceus
Fisheries and aquatic sciences. 2014. Dec, 17(4): 433-439
Copyright © 2014, The Korean Society of Fisheries and Aquatic Science
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial Licens ( permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
  • Received : June 25, 2014
  • Accepted : August 19, 2014
  • Published : December 31, 2014
Export by style
Cited by
About the Authors
Samad Rahimnejad
Kyeong-Jun Lee

We compared the utilization efficiency of free lysine (FL) and dipeptide lysine–glycine (LG) in terms of growth performance and whole-body amino acid composition in olive flounder Paralichthys olivaceus . A basal experimental diet was formulated to contain 0.5% (basal) lysine from fish meal, and four other diets were prepared by supplementing 0.5% or 1.0% of either FL or LG. The experiment was performed in triplicate, and 20 randomly selected fish averaging 5.41 ± 0.16 g were fed one of the test diets at the rate of 3% BW/day twice daily for 6 weeks. At the end of the feeding trial, fish fed the basal diet showed significantly less weight gain than did the other groups. The results of a two-way ANOVA showed that both lysine level ( P = 0.001) and type ( P = 0.034) influenced growth rate; however, we found no significant interaction between lysine level and form ( P > 0.05). Our results revealed a significant improvement in protein efficiency ratio (PER) with each increment of dietary lysine, and the groups fed LG-supplemented diets showed higher PER than did those offered FL. Hepatosomatic and viscerosomatic indices were significantly influenced by lysine level and form, and higher values were recorded in fish fed diets containing LG. Significantly higher whole-body arginine levels were found in LG-fed groups, and a significant interaction was observed between lysine level and form ( P = 0.009). Whole-body valine and aspartic acid contents were affected by lysine level, and alanine concentration was influenced by both lysine level and form. Our findings indicate that juvenile olive flounder can utilize LG more efficiently than FL for protein synthesis.
The quality of dietary protein is determined by its amino acid (AA) composition and availability ( Wilson and Cowey, 1985 ; Wilson and Poe, 1985 ). Quantitative estimation of the essential AA requirements of cultured fish species is very important to achieve optimum growth and feed utilization, cost-effective diet formulation, and desirable carcass quality ( NRC, 2011 ). It is well established that a balanced AA profile is required for the effective use of dietary protein in tissue synthesis ( D’Mello, 1994 ; Yamamoto et al., 2000 ; Berge et al., 2002 ; Green and Hardy, 2002 ; Gόmez-Requeni et al., 2003 ). AA can be supplied as protein-bound AA, free AA, or peptides in formulated diets. Absorption of peptides and free AA (FAA) are the major transport routes for protein use in mammals ( Ganapathy et al., 1994 ; Adibi, 1997 ). The current understanding of protein use in vertebrates centers on the absorption of peptides in the intestine as a major route of transport. In fishes, small peptides and FAA are absorbed faster than protein ( Rust et al., 1993 ; Rønnestad et al., 2003 ), and there is evidence that single peptides can be more efficiently absorbed than a mixture of identical AA in both fish ( Reshkin and Ahearn, 1991 ; Boge et al., 2002 ) and mammals ( Matthews, 1991 ). Previous studies on common carp Cyprinus carpio and rainbow trout Oncorhynchus mykiss showed inferior utilization of AA from FAA-based diets vs. that from protein-based diets ( Murai, ran1982 ; Kaushik and Dabrowski, 1983 ; Dabrowski et al., 2003 ), possibly because of deamination or higher total dietary nitrogen excretion through the gills and kidneys ( Dabrowski et al., 2003 ). It is generally thought that the inefficiency of free AA use in fish is due to faster uptake and subsequent catabolism compared with intact protein ( Cowey and Walton, 1988 ; Rønnestad et al., 2000 ; Dabrowski et al., 2003 ; Dabrowski et al., 2007 ). Another proposed explanation is higher leaching loss of free AA compared with bound AA in aquatic environments prior to ingestion ( Zarate and Lovell, 1997 ).
Dabrowski et al. (2003) showed that a synthetic dipeptide-based diet could support the early stages of rainbow trout growth, whereas a free AA-based diet could not. Peptides have different transport systems than FAA has. Tetra- and larger peptides do not cover nitrogen requirements in the absence of pancreatic enzymes or brush border peptidase activity ( Grimble, 1994 ; Daniel, 2004 ), whereas di- or tripeptides have specific peptide transporters ( Doring et al., 1998 ). These transporters are expressed in teleost larvae prior to exogenous feeding ( Verri et al., 2003 ).
Lysine has been identified as an essential AA for all studied fish species ( NRC, 2011 ) and has been found in high concentrations in the carcasses of many fishes ( Wilson and Cowey, 1985 ; Wilson and Poe, 1985 ; NRC, 1993 ). Lysine deficiency has been reported to result in decreased growth and low feed efficiency ( Ahmed and Khan, 2004 ; Wang et al., 2005 ; Zhou et al., 2008 ). It is the most limiting amino acid in the protein sources, particularly plant proteins, used in aquafeeds ( Deng et al., 2010 ).
Olive flounder Paralichthys olivaceus is an important marine cultured species in Korea, Japan, and China. Its total production reached ~37,000 tons in 2013 in Korea ( Ministry of Maritime Affairs and Fisheries of Korea, 2013 ). Dietary lysine requirements for the species were determined by Forster and Ogata (1998) using free L-lysine as the AA source. Kim and Lee (2013) showed that juvenile olive flounder can use dipeptide leucine more efficiently than its free form for protein synthesis. Accordingly, we compared the utilization efficiency of free and dipeptide forms of lysine in juvenile olive flounder diets.
Materials and Methods
- Experimental diets
Formulation and proximate composition of the experimental diets are shown in Table 1 . Five isonitrogenous (47% crude protein) and isocaloric (4.38 kcal g -1 gross energy) experimental diets were formulated to contain different levels and forms of lysine. A mixture of synthetic free AA without lysine was prepared according to Dabrowski et al. (2003) and used as the main protein source. A control diet was formulated to contain basal levels of lysine (0.5%) from fish meal and supplemented with 0.5% or 1.0% lysine in either the free or the dipeptide form. Lysine-Glycine (LG) (Bachem, Torrance, CA, USA) was used as the dipeptide form, and crystalline L-lysine (L-Lys) (Sigma Chemicals, St. Louis, MO, USA) as the free form (FL). The experimental diets were kept isonitrogenous using glycine at the expense of lysine. All ingredients were well mixed, pelletized, and freeze-dried. The pellets were crushed into desirable particle sizes and stored at –20°C until use.
Composition and proximate analysis of the experimental diets (% dry matter)
PPT Slide
Lager Image
1Free amino acid mixture composition (g per 446 g dry weight mixture): arginine hydrochloride, 15; valine, 12; methionine, 10; histidine, 7; isoleucine, 9; leucine, 14; phenylalanine, 18; threonine, 8; tryptophan, 2; glutamic acid, 111; glycine, 240. 2Mineral premix (g kg-1 mixture): MgSO4.7H2O, 80.0; NaH2PO4.2H2O, 370.0; KCl, 130.0; Ferric citrate, 40.0; ZnSO4.7H2O, 20.0; Ca-lactate, 356.5; CuCl2, 0.2; AlCl3. 6H2O, 0.15; Na2Se2O3, 0.01; MnSO4.H2O, 2.0; CoCl2.6H2O, 1.0. 3Vitamin premix (g kg-1 mixture): L-ascorbic acid, 121.2; DL-α tocopheryl acetate, 18.8; thiamin hydrochloride, 2.7; riboflavin, 9.1; pyridoxine hydrochloride, 1.8; niacin, 36.4; Ca-D-pantothenate, 12.7; myo-inositol, 181.8; D-biotin, 0.27; folic acid, 0.68; p-aminobezoic acid, 18.2; menadione, 1.8; retinyl acetate, 0.73; cholecalficerol, 0.003; cyanocobalamin, 0.003.
- Fish and experimental conditions
Juvenile olive flounder were transported from a private hatchery to the Institute of Marine Sciences at Jeju National University (Jeju, South Korea). All fish were fed the basal diet for 1 week to allow acclimation to both the semi-purified diet and the experimental conditions. At the end of the acclimation period, 20 randomly selected fish (averaging 5.41 ± 0.16 g) were stocked into polyvinyl circular tanks (20-L capacity), supplied with filtered seawater at a flow rate of 1.5 L min -1 , and aerated to maintain sufficient dissolved oxygen. Triplicate groups of fish were hand-fed with one of the test diets at a ratio of 3% of their body mass (twice a day, 09:00 and 17:00 h) for 6 weeks. The growth of fish was measured at 2-week intervals. Feeding was stopped 24 h prior to weighing to minimize handling stress. The water temperature during the feeding trial ranged from 14 to 20°C, and the photoperiod was maintained on a 12:12 light:dark schedule.
- Sample collection and analyses
At the end of the feeding trial, all fish in each tank were bulk-weighed and counted for growth parameters and survival. Five intact fish per tank (15 fish per treatment) were selected and kept at -20°C for whole-body amino acid composition analysis. The samples were freeze-dried and finely ground using a grinder, and their amino acid compositions was analyzed using an automatic amino acid analyzer (Biochrom 30, Pharmacia Biotech, Cambridge, England).
Another set of five fish per tank were sampled for determination of organosomatic indices, including hepatosomatic index (HSI), viscerosomatic index (VSI), and relative intestine length (RIL).
Analyses of the moisture and ash contents of the diets were performed using standard procedures ( Association of Official Analytical Chemists, 1995 ). Crude protein was measured using an automatic Kjeltec Analyzer Unit 2300 (FossTecator, Höganäs, Sweden), and crude lipid content was determined using the Soxhlet method with extraction in diethyl ether (Soxhlet Extraction System C-SH6, Korea).
- Statistical analysis
All experimental diets were assigned by a completely randomized design. Data were analyzed by one-way ANOVA using SPSS version 11.0 (SPSS, Inc., Chicago, IL, USA). When an ANOVA identified differences among groups, the means were compared using Tukey’s HSD multiple range test. Statistical significance was determined by setting the aggregate type 1 error at 5% ( P ≤ 0.05) for each set of comparisons. To isolate the effects of molecular form from lysine level in the two-way ANOVAs, only diets with lysine supplementation were considered. Data are presented as means ± SD. Percentage data were arcsine transformed before statistical analysis.
Results showed significant improvement in fish growth with each increment of dietary lysine ( P < 0.05, one-way ANOVA), and the highest growth performance occurred in fish fed 1.5% LG ( Table 2 ). Feed utilization was significantly affected by dietary treatment, and the highest protein efficiency ratio (PER) was obtained in fish fed 1.5% LG (one-way ANOVA). We also found significant effects of both lysine level and form on weight gain and PER ( P < 0.05, two-way ANOVA), but no interaction between them ( P > 0.05, two-way ANOVA). The survival rate ranged from 86 to 93% and did not significantly differ among treatments.
Growth performance of olive flounderParalichthys olivaceus(initial body weight, 5.41 ± 0.16 g) fed the experimental diets containing different lysine levels and molecular forms for 6 weeks
PPT Slide
Lager Image
Each value is the mean of triplicate groups. Values in the same row having different superscript letters are significantly different (P < 0.05). The lack of superscript letter indicates no significant differences among treatments. 1Pooled standard error of the mean 2Final body weight (g) 3Weight gain (%) = final mean body weight - initial mean body weight 4Protein efficiency ratio = Wet weight gain/total protein fed
Organosomatic indices of fish fed the experimental diets are presented in Table 3 . Significantly higher HSI and VSI were obtained in fish fed diets containing LG, and in those fed the free form diet at 1.5% ( P < 0.05, one-way ANOVA). Moreover, the two indices were significantly affected by both lysine form and level ( P < 0.05, two-way ANOVA). However, RIL did not differ significantly among treatments.
Organosomatic indices of olive flounderParalichthys olivaceus, (initial body weight, 5.41 ± 0.16 g) fed the experimental diets containing different lysine levels and molecular forms for 6 weeks
PPT Slide
Lager Image
Each value is the mean of triplicate groups. Values in the same row having different superscript letters are significantly different (P < 0.05). The lack of superscript letter indicates no significant differences among treatments. 1Pooled standard error of the mean 2Hepatosomatic index = 100 × (liver weight/body weight) 3Viscera somatic index = 100 × (viscera weight/body weight) 4Relative intestine length = 100 × (intestine length/total body length)
Whole-body amino acid composition was significantly affected by dietary treatment ( Table 4 ). Significantly higher arginine levels were found in fish fed diets containing LG (one-way ANOVA), and we found a significant interaction between lysine level and form (P = 0.009, two-way ANOVA). Two-way ANOVA analysis showed a significant effect of lysine level on whole-body valine and aspartic acid contents. Moreover, alanine content was significantly higher in fish offered 1.5% LG (one-way ANOVA), and it was significantly influenced by both lysine level and form.
Whole-body amino acid composition (% protein) of olive flounderParalichthys olivaceus, fed the experimental diets containing different lysine levels and molecular forms for 6 weeks
PPT Slide
Lager Image
Each value is the mean of triplicate groups. Values in the same row having different superscript letters are significantly different (P < 0.05). The lack of superscript letter indicates no significant differences among treatments. 1Pooled standard error of the mean.
Fish in our study accepted the semi-purified diets but grew relatively slowly because the trials occurred in low temperature season. Our results show a significant enhancement of fish growth with each increment of dietary lysine, indicating the importance of lysine for maximal growth in juvenile olive flounder. Forster and Ogata (1998) reported that the lysine requirement of olive flounder is 1.5–2.1% of their diet. Accordingly, we used a range of 0.5 to 1.5% lysine to compare the efficiency of its free and dipeptide forms.
Dabrowski et al. (2003) reported that a dipeptide-based diet could support the early-life growth performance of rainbow trout, whereas a FAA-based diet could not. In our study, fish fed LG supplemented diets showed higher growth than those fed FL, and the highest weight gain occurred in those fed 1.5% LG. Similarly, Kim and Lee (2013) found higher weight gain at all supplementation levels of the dipeptide form of leucine than of the free form. In contrast, Kim et al. (2012) reported similar efficiency for the dipeptide and free forms of phenylalanine when they supplemented in diets for red sea bream Pagrus major . Furthermore, Tesser et al. (2005) found that juvenile South American pacu Piaractus mesopotamicus can utilize dipeptide arginine for growth with similar efficiency. Moreover, the results of a study on koi carp Cyprinus carpio revealed no difference in growth performance between free and dipeptide AA ( Kwasek et al., 2010 ). Absorption of free AA is faster than that of protein-bound AA, and may result in AA imbalances and subsequent low protein utilization ( Rønnestad et al., 2000 ). Moreover, an excess of di- or tripeptides can be similarly problematic due to the saturation of their transport mechanisms ( Verri et al., 2003 ) or their instant hydrolysis to free AA ( Carvalho et al., 2004 ). However, better absorption of single peptides compared with an equivalent mixture of free AA has been reported in rainbow trout ( Boge et al., 1981 ). It has also been reported that the substitution of protein-bound AA by di- and tripeptides at rates up to 20% enhanced the growth performance of European sea bass larvae, whereas higher substitution levels decreased growth ( ZamboninoInfante et al., 1997 ).
Composition of the basal diet is an important factor influencing the results of dipeptide AA supplementation. In this study, the utilization efficiencies of the two lysine forms were examined by supplementing them into a free AA-based basal diet, whereas previous studies have supplemented wholeprotein based diets ( Tesser et al., 2005 : Kwasek et al., 2012 ). The differences in AA availability from free AA and wholeprotein-based diets may at least partially explain the observed variations. Moreover, it has been suggested that the use of different dipeptides can profoundly affect absorption characteristics by switching the AA sequence ( Daniel, 2004 ). Cytosolic and brush border aminopeptidases are involved in the utilization of dietary peptides ( Cahu and ZamboninoInfante, 1995 ; Kurokawa and Suzuki, 1998 ). However, further studies are required to clarify the mechanism by which dipeptides mediate specific peptide transporters in the intestinal brush border epithelium.
We showed that both lysine level and form affected the weight gain of olive flounder. Kim and Lee (2013) reported that the molecular form of leucine, and not its level, was the main factor in olive flounder growth performance. This variation may be due to differences in fish size, feeding period, dietary requirements, and experimental conditions.
The study of HSI and VSI provides important information on the metabolism of fishes, especially as related to digestion and absorption, and on the synthesis and secretion of digestive enzymes ( McLaughlin, 1983). HSI is used as an indicator of general nutritional status ( Busacker et al., 1990 ). We obtained significantly higher HSI and VSI values with each increment of dietary lysine; this was more evident when the dipeptide form was used, indicating a higher energy budget in LG fed fish.
The whole-body AA profile has been used as a standard indicator of fish AA requirements ( Wilson and Cowey, 1985 ; Bicudo and Cyrino, 2009 ). Several studies have shown that whole-body essential AA profiles provide a good estimate of the optimum essential AA profile in fish diets ( Akiyama et al., 1997 ; Green and Hardy, 2002 ). Aragão et al. (2004) showed that juvenile Senegal sole Solea senegalensis exhibited improved general AA deposition in the body when they were offered a diet containing dipeptide AA. Our results showed a significant effect of dietary treatments on whole-body AA composition. We found higher whole-body accumulation of arginine when fish were provided LG, and detected a significant interaction between lysine level and form. A similar tendency was observed for alanine concentration, where higher values were obtained for LG fed groups. In line with our results, Kwasek et al. (2010) found significantly lower concentrations of threonine, arginine, valine, methionine, isoleucine, leucine, phenylalanine, and lysine in the whole body of koi carp fed a free AA-based diet compared with those fed a dipeptide-based diet. However, the results of previous studies on common carp ( Cyprinus carpio L. ) ( Zhang et al., 2006 ), red sea bream ( Kim et al., 2012 ), and olive flounder ( Kim and Lee, 2013 ) did not show any significant changes in whole-body/muscle AA composition when the fish were provided with free or dipeptide forms of AA. Dabrowski et al. (2005) proposed that the differences in muscle free AA composition in fish offered different dietary AA sources are due to differences in the absorption rates for free and dipeptide AA, leading to uneven accumulation rates of muscle free AA, ultimately resulting in different metabolic rates and AA availability for protein synthesis. Our findings show that AA availability could improve in fish fed with dipeptide forms vs. those fed free forms.
In conclusion, juvenile olive flounder can utilize lysine more efficiently for growth if it is provided in dipeptide form, and the dipeptide form can improve AA retention in fish. Overall, we provide further evidence for the notion that previously published data on AA requirements using free AA are likely to be overestimated and need to be reevaluated using dipeptides as the AA source.
This research was supported by Basic Science Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (Grant number: NRF-2010-0009918).
Adibi SA 1997 The oligopeptide transporter (Pept-1) in human intestine: biology and function Gastroenterology 113 332 - 340    DOI : 10.1016/S0016-5085(97)70112-4
Ahmed I , Khan MA 2004 Dietary lysine requirement of fi ngerling Indian major carp, Cirrhinus mrigala (Hamilton) Aquaculture 235 499 - 511    DOI : 10.1016/j.aquaculture.2003.12.009
Akiyama T , Oohara I , Yamamoto T 1997 Comparison of essential amino acid requirement with A/E ratio among fish species (Review Paper) Fish Sci 63 963 - 970
1995 Official Methods Analysis 16th ed Association of Official Analytical Chemists Arlington, VA, US
Aragăo C , Conceicao LEC , Martins D , Rønnestad I , Gomes E , Dinis T 2004 A balanced dietary amino acid profi le improves amino acid retention in post-larval Senegalese sole (Solea senegalensis) Aquaculture 233 293 - 304    DOI : 10.1016/j.aquaculture.2003.08.007
Berge GE , Sveier H , Lied E 2002 Effects of feeding Atlantic salmon (Salmo salar L.) imbalanced levels of lysine and arginine Aquacult Nutr 8 239 - 248    DOI : 10.1046/j.1365-2095.2002.00211.x
Bicudo AJA , Cyrino JEP 2009 Estimating amino acid requirement of Brazilian freshwater fish from muscle amino acid profile J World Aquacult Soc 40 818 - 823    DOI : 10.1111/j.1749-7345.2009.00303.x
Boge G , Rigal A , Peres G 1981 Rates of in vivo intestinal absorption of glycine and glycyglycine by rainbow trout (Salmo gairdneri R.) Comp Biochem Physiol 69 455 - 459    DOI : 10.1016/0300-9629(81)93004-8
Boge G , Roche H , Balocco C 2002 Amino acid transport by intestinal brush border vesicles of a marine fish Boops salpa Comp Biochem Physiol B 131 19 - 26    DOI : 10.1016/S1096-4959(01)00474-2
Busacker GP , Adelman IR , Goolish EM , Schreck C.B. , Moyle P.B. 1990 Methods for Fish Biology American Fisheries Society Bethesda (MD) Growth 363 - 387
Cahu N , ZamboninoInfante J 1995 Effect of the molecular-form of dietary nitrogen supply in sea bass larvae-response of pancreatic-enzymes and intestinal peptidases Fish Physiol Biochem 14 209 - 214    DOI : 10.1007/BF00004311
Carvalho AP , Sa R , Oliva-Teles A , Bergot P 2004 Solubility and peptide profi le affect the utilization of dietary protein by common carp (Cyprinus carpio) during early larval stages Aquaculture 234 319 - 333    DOI : 10.1016/j.aquaculture.2004.01.007
Cowey CB , Walton MJ 1988 Studies on the uptake of (14C) amino acids derived from both dietary (14C) protein and dietary (14C) amino acids by rainbow trout, Salmo gairdneri Richardson J Fish Biol 33 293 - 305    DOI : 10.1111/j.1095-8649.1988.tb05472.x
Dabrowski K , Lee KJ , Rinchard J 2003 The smallest vertebrate teleost fish can utilize synthetic dipeptide-based diets J Nutr 133 4225 - 4229
Dabrowski K , Terjesen BF , Zhang Y , Phang JM , Lee KJ 2005 A concept of dietary dipeptides: a step to resolve the problem of amino acid availability in the early life of vertebrates J Experimental Biol 208 2885 - 2894    DOI : 10.1242/jeb.01689
Dabrowski K , Arslan M , Terjesen BF , Zhang Y 2007 The effects of dietary indispensable amino acid imbalances on feed intake: Is there a sensing of deficiency and neural signaling present in fish? Aquaculture 268 036 - 142
Daniel H 2004 Molecular and integrative physiology of intestinal peptide transport Ann Rev Physiol 66 361 - 384    DOI : 10.1146/annurev.physiol.66.032102.144149
Deng DF , Dominy W , Ju ZY , Koshio S , Murashige R , Wilson RP 2010 Dietary lysine requirement of juvenile Pacific threadfin (Polydactylus sexfilis) Aquaculture 308 44 - 48    DOI : 10.1016/j.aquaculture.2010.07.041
D’Mello JPF 1994 Amino Acids in Farm Animal Nutrition CAB International allingford, UK
Doring F , Will J , Amasheh S , Clauss W , Ahlbrecht H , Daniel H 1998 Minimal molecular determinants of substrates for recognition by the intestinal peptide transporter J Biol Chem 273 23211 - 23218    DOI : 10.1074/jbc.273.36.23211
Forster I , Ogata HY 1998 Lysine requirement of juvenile Japanese flounder Paralichthys olivaceus and juvenile red sea beam Pagrus major Aquaculture 161 131 - 142    DOI : 10.1016/S0044-8486(97)00263-9
Ganapathy V , Brandsch M , Leibach FH. , Johnson L. R. , Christensen J. 1994 Physiology of Gastrointestinal tract Raven Press New York, USA Intestinal transport of amino acids and peptides 1773 - 1794
Green JA , Hardy RW 2002 The optimum dietary essential amino acid pattern for rainbow trout (Oncorhynchus mykiss) to maximize nitrogen retention and minimize nitrogen excretion Fish Physiol Biochem 27 97 - 108    DOI : 10.1023/B:FISH.0000021878.81647.6e
Grimble G 1994 The signifi cance of peptides in clinical nutrition Ann Rev Nutr 14 419 - 447    DOI : 10.1146/
Gómez-Requeni P , Mingarro M , Kirchner S , Calduch-Giner JA , Medale F , Corraze G , Panserat S , Martin SAM , Houlihan DF , Kaushik SJ , Perez-Sanchez J 2003 Effects of dietary amino acid profi le on growth performance, key metabolic enzymes and somatotropic axis responsiveness of gilthead sea bream (Sparus aurata) Aquaculture 220 749 - 767    DOI : 10.1016/S0044-8486(02)00654-3
Kaushik SJ , Dabrowski K 1983 Postprandial metabolic changes in larval and juvenile carp (Cyprinus carpio) Reprod Nutr Develop 23 223 - 234    DOI : 10.1051/rnd:19830207
Kim SS , Rahimnejad S , Song JW , Lee KJ 2012 Comparison of growth performance and whole-body amino acid composition in red seabream (Pagrus major) fed free or dipeptide form of phenylalanine Asian-Aust J Anim Sci 25 1138 - 1144    DOI : 10.5713/ajas.2012.12054
Kim SS , Lee KJ 2013 Comparison of leucine requirement in olive flounder (Paralichthys olivaceus) by free or synthetic dipeptide forms of leucine Anim Feed Sci Technol 183 195 - 201    DOI : 10.1016/j.anifeedsci.2013.05.008
Kurokawa T , Suzuki T 1998 Development of intestinal brush border aminopeptidase in the larval Japanese flounder Paralichthys olivaceus Aquaculture 162 113 - 124    DOI : 10.1016/S0044-8486(98)00171-9
Kwasek K , Zhang Y , Dabrowski K 2010 Utilization of dipeptide/protein based diets in larval and juvenile koi carp-post-prandial free amino acid levels J Anim Physiol Anim Nutr 94 35 - 43    DOI : 10.1111/j.1439-0396.2008.00877.x
Kwasek K , Terova G , Wojno M , Dabrowski K , Wick M 2012 The effect of dietary dipeptide lysine–glycine on growth, muscle proteins, and intestine PepT1 gene expression in juvenile yellow perch Rev Fish Biol Fish 22 797 - 812    DOI : 10.1007/s11160-012-9266-6
Matthews D 1991 Protein Absorption Wiley-Liss New York
McLaughlin PA. , Bliss DE , Mantel TH 1983 The Biology of Crustacea Academic Press New York, U.S.A. Internal anatomy 1 - 52, 479
2013 Aquaculture Statistic from Ministry of Maritime Affairs and Fisheries of Korea
Murai T 1982 Effect of coating amino acids with casein supplmented to gelatin diet on plasma free amino acids of carp Bull Jap Soc Sci Fish 48 703 - 710    DOI : 10.2331/suisan.48.703
1993 National Research Council Nutrient Requirements of Fish National Academy Press Washington, DC., USA
2011 Nutrient Requirements of Fish Natl Academy Press Washington, DC, USA
Reshkin S , Ahearn G 1991 Intestinal glycyl-L-phenylalanine and L-phenylalanine trasnport in a euryhaline teleost Am J Physiol 260 R563 - R569
Rønnestad I , Conceicao LEC , Aragai C , Dinis MT 2000 Free amino acids are absorbed faster and assimilated more efficiently than protein in postlarval Senegal sole (Solea senegalensis) J Nutr 130 2809 - 2812
Rønnestad I , Tonheim SK , Fyhn HJ , Rojas-Garcia CR , Kamisaka Y , Koven W 2003 The supply of amino acids during early feeding stages of marine fish larvae: a review of recent findings Aquaculture 227 147 - 164    DOI : 10.1016/S0044-8486(03)00500-3
Rust MB , Hardy RW , Stickney RR 1993 A new method for force feeding larval fish Aquaculture 116 341 - 352    DOI : 10.1016/0044-8486(93)90418-X
Tesser M , Terjesen BF , Zhang Y , Portella MC , Dabrowski K 2005 Free- and peptide-based dietary arginine supplementation for the South American fish pacu (Piaractus mesopotamicus) Aquacult Nutr 11 443 - 453    DOI : 10.1111/j.1365-2095.2005.00373.x
Verri T , Kottra G , Romano A , Tiso N , Peric M , Maffia M , Boll M , Argenton F , Daniel H , Storelli C 2003 Molecular and functional characterisation of the zebrafish (Danio rerio) PEPT1-type peptide transporter FEBS Lett 549 115 - 122    DOI : 10.1016/S0014-5793(03)00759-2
Wang S , Liu YJ , Tian LX , Xie MQ , Yang HJ , Wang Y , Liang GY 2005 Quantitative dietary lysine requirement of juvenile grass carp Ctenopharyngodon idella Aquaculture 249 419 - 429    DOI : 10.1016/j.aquaculture.2005.04.005
Wilson RP , Cowey CB 1985 Amino acid composition of whole body tissue of rainbow trout and Atlantic salmon Aquaculture 48 373 - 376    DOI : 10.1016/0044-8486(85)90140-1
Wilson RP , Poe WE 1985 Relationship of whole body and egg essential amino acid patterns to amino acid requirement patterns in channel catfish, Ictalurus punctatus Comp Biochem Physiol 80 385 - 388
Yamamoto T , Shima T , Furuita H , Shiraishi M , Sanchez-Vasquez FJ , Tabata M 2000 Self-selection of diets with different amino acid profiles by rainbow trout (Oncorhynchus mykiss) Aquaculture 187 375 - 386    DOI : 10.1016/S0044-8486(00)00320-3
ZamboninoInfante JL , Cahu CL , Peres A 1997 Partial substitution of di- and tripeptides for native proteins in sea bass diet improves Dicentrarchus labrax larval development J Nutr 127 608 - 614
Zarate DD , Lovell RT 1997 Free lysine (L-lysine.HCL) is utilized for growth less efficiently than protein-bound lysine (soybean meal) in practical diets by young channel catfish (Ictalurus punctatus) Aquaculture 159 87 - 100    DOI : 10.1016/S0044-8486(97)00184-1
Zhang Y , Dabrowski K , Hliwa P , Gomulka P 2006 Indispensable amino acid concentrations decrease in tissues of stomachless fish, common carp in response to free amino acid- or peptide-based diets Amino Acids 31 165 - 172    DOI : 10.1007/s00726-006-0345-7
Zhou XQ , Zhao CR , Jiang J , Feng L , Liu Y 2008 Dietary lysine requirement of juvenile Jian carp (Cyprinus carpio var. Jian) Aquacult Nutr 14 381 - 386    DOI : 10.1111/j.1365-2095.2007.00535.x