An effective source of dietary methionine for the turbot Psetta maxima


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The turbot Psetta maxima is an important cultured flatfish species in Europe and now increasingly in China. Dietary formulations for this species typically have been dependent on high levels of fishmeal inclusion. Increasing costs and the decreasing availability of fishmeal have necessitated lowering fishmeal levels and increasing plant proteins in feed formulations.

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An effective source of dietary methionine for the turbot Psetta maxima

  1. 1. May | June 2013An effective source of dietary methioninefor the turbot Psetta maximaThe International magazine for the aquaculture feed industryInternational Aquafeed is published six times a year by Perendale Publishers Ltd of the United Kingdom.All data is published in good faith, based on information received, and while every care is taken to prevent inaccuracies,the publishers accept no liability for any errors or omissions or for the consequences of action taken on the basis ofinformation published.©Copyright 2013 Perendale Publishers Ltd.All rights reserved.No part of this publication may be reproduced in any formor by any means without prior permission of the copyright owner. Printed by Perendale Publishers Ltd. ISSN: 1464-0058INCORPORATINGf ish farming technolog y
  2. 2. The turbot Psetta maxima is an important cultured flatfish species in Europe and now increasingly in China. Dietary formulations for this species typically have been dependent on high levels of fishmeal inclusion. Increasing costs and the decreasing availability of fishmeal have necessitated lowering fishmeal levels and increasing plant proteins in feed formulations.In such diets methionine can become one of the first limiting amino acids and supple-mentation is frequently necessary to balance diets and achieve optimum performance. The hydroxy analog of methionine, 2-hydroxy-4-methylthio butanoic acid (HMTBa) is a safe and effective source of methionine that has been used to supplement methionine deficient diets for livestock and aquaculture species. HMTBa is structurally different from L-methionine in that it has a hydroxyl group instead of an amino group at the α-carbon position, potentially reducing feed nitrogen inputs into grow out systems. It is passively absorbed and is converted to L-methionine by D-hydroxy acid dehydrogenase and L-hydroxy acid oxidase enzymes which have been confirmed in tissues of shrimp and fish. A two-part study was carried out at the Ocean University of China, China to evaluate 1. The response of turbot fed diets sup-plemented with either HMTBa (2-hydroxy-4-methylthio-butanoic acid) or L-methionine, and 2. The dynamics of absorption of HMTBa and L-methionine.Materials and methodsA 75-day growth trial was carried out to evaluate the effects of HMTBa and L-methionine as dietary methionine sources on the growth of juvenile turbot (initial weight 5.6 g. N=5 tanks per treatment). Five levels (0.3, 0.6, 0.9, 1.2 and 1.5% dry matter) of HMTBa (added as Mera™Met – 84 percent HMTBa; Novus International Inc., USA) and L-methionine were added respectively to a practical basal diet, that was limiting in methionine (0.59% methionine; 0.42% cystine; 1.01% total sulfur amino acids). This basal diet served as the control diet and contained 48 percent crude protein and approximately 12.5% crude lipid. A crystalline L-amino acid premix, which was devoid of sulfur amino acids was added to the basal diet to approximate the whole body composition of the turbot. Different levels of either HMTBa or L-methionine were added to the basal diet at the expense of glutamic acid to give total methionine con-centrations rang-ing from 0.59 - 2.09 and total sulfur amino acid concentrations ranging from 1.01 to 2.51%. A second study was conducted to evaluate the absorption of HMTBa and L-methionine from diets containing these methionine sources. The basal diet used in the second trial was generally similar to that used in the growth trial (0.75% methionine and 0.45% cystine; total sulfur amino acid concentration of 1.20%). The basal diet was Figure 1: Weight gain and specific growth rate in juvenileturbot fed either HMTBa or L-methionineAn effective source ofdietary methionine for theturbot Psetta maximaby Rui Ma1, Huapeng Hou1, Wenbing Zhang1, Anant Bharadwaj2, Craig Browdy2and Kangsen Mai138 | InternatIonal AquAFeed | May-June 2013FEATURE
  3. 3. supplemented with either 0.75% HMTBa or L-methionine. In this trial larger fish (65 g; 45 fish/tank; N=3) were used to facilitate blood sampling at the end of the trial. The basal control diet and the two experi-mental diets were fed to the turbot for a period of 14 days twice daily to apparent satiation. Fish were fasted 12 h prior to final feeding. Following feeding, fish were sampled at 0, 0.25, 0.5, 1, 2, 3, 4, 6, 9, 12, 18 and 24 h respectively and their blood collected. Blood was centrifuged and serum collected and stored prior to analysis. Serum was analyzed using HPLC for HMTBa and free methionine.ResultsThere were no significant differences in survival between treatments. Fish fed the basal diet (red bar) showed significantly lower weight gain than all the other treatments (Figure 1). Weight gain in fish fed both methionine sources increased in a quad-ratic fashion with increasing dietary concentration. In fish fed HMTBa (blue bars) maxi-mum response was observed at 0.9% supplementation and was significantly NUTRACEUTICALS AND PHYTOBIOTICSFOR AQUACULTUREGrowth promotersAnti-parasitesAttractantsHepatoprotectorsAntioxidantsDetoxifiersChelated mineralsADDITIVES FOR AQUACULTURE SOLUTIONSC/ San Romualdo 12-14 • 28037 Madrid (Spain)+34 902 15 77 11 • +34 91 725 08 • www.liptosa.comFigure 2a: Serum free-methionine concentrations in post-fed turbot fed the control, L-methionine and HMTBa dietsFigure 2b: Serum HMTBa concentrations in fish fed dietscontaining HMTBaMay-June 2013 | InternatIonal AquAFeed | 39FEATURE
  4. 4. higher than the response seen in fish sup-plemented 0.9% L-methionine. Generally, at doses ranging from 0.6 to 1.5%, fish fed HMTBa showed equal or higher weight gain compared to fish fed L-methionine (green bars). Similar responses were observed for other performance parameters such as final weight, specific growth rate, feed efficiency, protein efficiency ratio and protein retention.Results from the analysis of serum show that the maximum serum concentra-tion of free-methionine (435.13µmol/L) in L-methionine-fed fish was observed at 9 h after feeding (Figure 2a) whereas the maxi-mum serum HMTBa level (426.17µmol/L) in HMTBa-fed fish occurred 6 h after feeding (Figure 2b). Appreciable quantities of HMTBa were observed in the serum of HMTBa-fed fish shortly after feeding as expected based on passive diffusion of HMTBa across the gut wall in fish. Two free methionine peaks were measured in the serum of HMTBa-fed fish at 3-4 h and 12 h post-feeding. This suggests contributions from either HMTBa metabolism to L-methionine, tissue protein turnover or digestion of intact dietary proteins. These data suggest that HMTBa is absorbed into circulation in fish shortly after feeding and also show that the maximum serum concentra-tions of HMTBa in HMTBa-fed fish are similar to serum free-methionine concentrations in L-methionine fed fish.ConclusionsThe results of these trials confirm that HMTBa is a safe and available source of methionine in practical diets for the turbot Psetta maxima. The HMTBa was absorbed efficiently into circulation at rates that are similar or better than L-methionine. Dynamics confirmed direct absorption demonstrated in previous livestock studies. Mera™Met can provide a cost effective methionine source in reduced fishmeal formulations with 100 percent bioavailability. HMTBa has been shown in previous studies to improve feed attractability, providing an effective alterna-tive for optimizing performance and allow-ing for higher cost efficiencies through the replacement of fishmeal by plant meals in aquatic feeds.More InforMatIon:1The Key Laboratory of Mariculture, OceanUniversity of China, ChinaEmail: International Inc., USAEmail: craig.browdy@novusint.comWebsite: www.novusint.com40 | InternatIonal AquAFeed | May-June 2013FEATURE
  5. 5. May-June 2013 | InternatIonal AquAFeed | 41FEATURECLOSER LOOKtake aat Novus Aquaculture® is a trademark of Novus International, Inc., and is registered in the United States and other countries. TM SOLUTIONS SERVICE SUSTAINABILITYis a trademark of Novus International, Inc. ©2012 Novus International, Inc. All rights reserved. COST REDUCTION | HEALTH THROUGH NUTRITION | OPTIMIZED RAW MATERIALS | FUNCTIONAL FEEDS | SUSTAINABLE PRACTICESOur success in developing sustainablesolutions evolves from a hands-on knowledgeand understanding of the global aquaindustry. By focusing on the needs of theanimals, our team of experts will design asolution for your operation.International Aquafeed has teamed up with to offer our readers a 15% discountThe world’s finest brass-based fishing luresmanufactured by hand in New ZealandYour order will be processed and dispatched from our production unit within 24 hoursEven fi sh farmers like fi shing!www.lurestore.comA & AJ Gilbert Fishing Tackle, New ZealandREF: IAF303-PPLPlace your order today atSPANISHLANGUAGEEDITIONwww.aquafeed.coEDICIONESPANOLA
  6. 6.• See the full issue• Visit the International Aquafeed website• Contact the International Aquafeed Team• Subscribe to International AquafeedThey are what they eatEnhancing the nutritional value of live feedswith microalgaeControlling mycotoxins withbindersUltravioletwater disinfection for fishfarms and hatcheriesNiacin– one of the key B vitamins for sustaininghealthy fish growth and productionVolume 16 Issue 3 2013 - mAY | Ju NeINCORPORATINGfIsh fARmING TeChNOlOGyThis digital re-print is part of the May | June 2013 edition of InternationalAquafeed magazine. Content from the magazine is available to view free-of-charge, both as a fullonline magazine on our website, and as an archive of individual features onthe docstoc website.Please click here to view our other publications on purchase a paper copy of the magazine, or to subscribe to the paperedition please contact our Circulation and Subscriptions Manager on the linkabove. INFORMATION FOR ADVERTISERS - CLICK HERE