Aquaculture nutrition, tập 19, số 4, 2013

Aquaculture Nutrition 2013 19; 441448 doi: 10.1111/anu.12050 Department of Fisheries and Allied Aquacultures, Auburn University, Auburn, AL, USA The production of the Pacific white shrimp (Litopenaeus vannamei) has expanded to the point of being the most widely cultured species of shrimp One of the advantages of this species is its acceptance of a wide variety of feed formulations including plant-based feeds Given the increases in ingredient costs, particularly fish meal, there is considerable interest in the use of alternative feed formulations for cultured species Given that soybean meal is one of the most widely available protein sources for which production can be expanded, the move to soy-based diets is inevitable The successful use of alternative feed ingredients for shrimp production depends on a number of factors This paper summarizes studies regarding the move towards high soy diets concerning manipulation of ingredients and nutrient profiles to maintain balanced feed formulations KEY WORDS: alternative feed, practical diets, soybean, van- namei Received September 2011, accepted 20 January 2013 Correspondence: D.A Davis, Department of Fisheries and Allied Aquacultures, 203 Swingle Hall, Auburn University, Auburn, AL 36849-5419, USA E-mail: davisda@auburn.edu Pacific white shrimp, Litopenaeus vannamei (Boone) is native to the eastern Pacific Ocean from Sonora, Mexico to Northern Peru Currently, it is the most popular cultured shrimp species and has experienced a dramatic increase in aquaculture production from 186 113 tonnes in 1999 to 296 630 tonnes in 2007 (FAO 2009) The industry growth has been paralleled by an increase in shrimp feed production The increases in demand and limitations of supply ê 2013 John Wiley & Sons Ltd have resulted in some ingredients becoming less available and more costly, especially fish meal and fish oil Fish meal and other marine ingredients are considered desirable ingredients in shrimp feed because of their nutrient content and palatability In commercial feeds, fishmeal typically accounts for 200300 g kg1 of the shrimp feed formulation (Tacon & Metian 2008) The cost of fish meal and fish oil has generally increased over time as a result of the uncertainty of availability and large fluctuations in the price Furthermore, there are growing social and environment concerns regarding the long-term sustainability of the use of marine ingredients In addition to feed prices increasing, the market value for shrimp has declined because of increased production and limited demand This has resulted in a reduction in the profit margin for shrimp farmers When margins were good, feed manufacturers could afford to use expensive ingredients and over formulate a diet However, as the margin decreased, feeds must become more cost-effective Feed costs can account for as much as 4060% of production costs (Hertrampf & Piedad-Pascual 2000) Feed costs and feed management both influence the investment in feeds Reducing or removing costly protein sources through the use of a combination of less expensive and more economical protein and lipid sources could result in substantial saving in feed cost Practical diets using plant-based ingredients to replace fish meal and fish oil have become an interesting alternative which could reduce these problems The use of renewable plant protein sources has become the focus of protein substitution studies in shrimp feeds around the world because of their acceptable protein level, suitable amino acid content, economic opportunity and consistent quality (Watanabe 2002) Formulated diets are designed to contain sufficient levels of nutrients to meet requirements using plant-based protein sources for which production can be expanded and are often more cost-effective Feeding plant-based proteins to shrimp requires that the ingredients possess certain nutritional characteristics, such as low levels of fibre, starch (especially insoluble carbohydrates) and antinutrients They must also contain a relatively high protein content, favourable amino acid profile, high nutrient digestibility and reasonable palatability (Gatlin et al 2007; Naylor et al 2009) Ten indispensable amino acids that are required for growth and maintenance of shrimp are arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine (Kanazawa 1989; Guillaume 1997) These amino acids should satisfy shrimp requirements to support optimum growth performance Fish meal is considered ideal protein source for fish and shrimp feed production because of its high level of essential amino acids On the other hand, plant protein sources contain lower levels of some essential amino acids (Tacon 1994) Thus, the balance of essential amino acids must be considered when diets are formulated to contain plant protein sources to replace fish meal In general, the amino acid profile of soybean meal is comparable with that of fish meal, albeit is lower in sulphur amino acids, that is, methionine and cystine (Peres & Lim 2008) Soybean meal is often considered as the most reliable ingredient and cost-effective protein source in shrimp feed because of its high protein content, high digestibility, relatively well-balanced amino acid profile, reasonable price and steady supply (Davis & Arnold 2000; Amaya et al 2007a,b) The protein digestibility was found higher in soybean protein than that in the marine animal meals (Akiyama 1989) Ezquerra et al (1997, 1998) reported in vivo and in vitro protein digestibility by pH drop of feed using the white shrimp hepatopancreas ranged from 64% to 91% where soybean protein showed greater APD than those in fish meal or crab meal (Table 1) However, the inclusion of soybean meal at high levels or as a sole protein source has resulted in reduced performance of the shrimp (Lim & Dominy 1990) This could be the results of imbalanced amino acid profiles or deficiencies of other dietary nutrients that were not taken into account Fish meal is utilized as a protein source but it also provides lipids, essential fatty acids (EFAs), minerals and vitamins to the diet Consequently, there will be most likely a need to use a variety of feed ingredients in association with soybean meal to provide a better balanced nutrient profile Utilization of various potential protein sources in shrimp feeds such as animal by-product and other plant sources (listed in table 2) has been evaluated under different rearing conditions (Lim & Dominy 1990; Piedad-Pascual et al 1990; Sudaryono et al 1995; Cruz-Suarez et al 2001; Amaya et al 2007a,b; Ray et al 2009) One of those ingredients that are considered a promising alternative for the substitution of fish meal in shrimp feeds is poultry by-product meal (Davis & Arnold 2000; Samocha et al 2004; Amaya et al 2007a; Markey 2007) Distillers dried grains with solubles (DDGS) is also a potential protein source for shrimp feed because of its low cost and consistent supply as a coproduct of the bio-ethanol production, which is expected to increase rapidly in the next decade Several studies reported the successful use of DDGS as an alternative protein source in fish and crustacean feeds without causing negative impact on growth performance (Webster et al 1991, 1992; Wu et al 1994; Cheng & Hardy 2004; Coyle et al 2004; Stone et al 2005; Lim et al 2007, 2009; Robinson & Li 2008; Thompson et al 2008) Pea meal is also another widely used feed Table Chemical composition of the test ingredients and in vivo and in vitro protein digestibility of L vannamei fed different protein sources Results expressed as meanặSD Ingredients Moisture1 Chilean anchovy Deboned white fish Langostilla Mexican tuna waste Menhaden fish meal A Menhaden fish meal B Soybean protein 104 54 59 49 78 83 93 ặ ặ ặ ặ ặ ặ ặ 3 10 5 Crude protein1 602 757 394 613 638 609 495 ặ ặ ặ ặ ặ ặ ặ 10 10 10 10 Crude fat1 Ash1 ặ ặ ặ ặ ặ ặ ặ 148 93 426 215 181 159 215 125 72 29 64 119 145 53 6 ặ ặ ặ ặ ặ ặ ặ 0.5 1 In vivo2 digestibility In vitro3 digestibility 83.6 86.6 66.4 63.6 67.1 68.4 90.9 81.5 86.3 75.7 70.0 70.5 64.9 83.7 g kg1 dry matter basis Determined by chromic oxide method using 3.54 g shrimp, N = tanks/treatment (from Ezquerra et al 1997) Determined by pH drop at 27 C of feed using enzymes extracted from hepatopancreas of 10 to 12 g white shrimp (from Ezquerra et al 1998) Aquaculture Nutrition 19; 441448 ê 2013 John Wiley & Sons Ltd Table Chemical composition of the test ingredients (as-fed basis) (NRC 2011) Ingredient Fish meal Anchovy Menhaden White DDGS Pea meal Poultry by-product Soybean meal 44% CP 48% CP Soy protein concentrate Dry matter (g kg1) Crude protein (g kg1) Crude fat (g kg1) Crude fibre (g kg1) Ash (g kg1) 920 920 920 910 900 890 654 645 620 270 253 559 76 96 78 93 14 136 10 91 69 21 143 190 213 64 33 145 890 900 920 440 485 636 15 73 34 45 63 58 ingredient, mostly in livestock because of its high energy, moderate protein level (220260 g kg1 crude protein), amino acid profile and low cost (Borlongan et al 2003) Several studies indicated that feed pea is another potential ingredient in fish and shrimp feeds (Gomes et al 1995; Burel et al 2000; Carter & Hauler 2000; Gouveia & Davies 2000; Booth et al 2001; Cruz-Suarez et al 2001; Davis et al 2002; Bautista-Teruel et al 2003; Borlongan et al 2003) Because of the limitation in nutrient component of most ingredients, more than one ingredient is required for balanced feed formulations Therefore, shrimp diets containing soybean meal as a main protein source should be combined with other alternative protein ingredients, that is, poultry by-product meal, DDGS and pea meal Soybean and its products are acceptable protein sources with good digestibility for shrimp However, soybean meal is deficient in the essential amino acids (EAAs) such as methionine, lysine and tryptophan as well as essential fatty acids and minerals (Lim & Dominy 1990) Methionine is one of the ten essential or indispensable amino acids that are dietary essential for shrimp (Millamena et al 1996) Thus, supplementation of sulphur amino acids, that is, methionine or cystine, in soybean-based diets to meet the shrimp requirement is recommended to provide a good growth response (Akiyama 1989) Low levels of methionine found in soybean meal can also be countered by mixing with other protein sources and/or the supplementation of synthetic methionine Several studies had reported successfully replacing fish meal with soybean meal with a methionine supplement in Milkfish (Davis et al 1995; Shiau et al 2007) Conversely, a diet containing only soybean protein with a methionine supplement was poorly utilized by red drum (Reigh & Ellis 1992) McGoogan & Gatlin (1997) suggested that diets containing soybean meal with low levels or no fish meal may have palatability problems Thus, Aquaculture Nutrition 19; 441448 ê 2013 John Wiley & Sons Ltd the inclusion of attractants or palatability enhancers, for example, fish solubles, may be considered A reduction in feed intake was reported in largemouth bass fed diets with increased soybean meal levels (Cho et al 1974; Kubitza et al 1997) Similar results were observed in red drum (Reigh & Ellis 1992; Davis et al 1995) and Pacific white shrimp (Lim & Dominy 1990) Along with protein, lipids constitute the major macronutrients that are required to provide the energy and cellular building blocks as well as maintain growth, health, welfare and reproduction in shrimp (Lim et al 1997) Reducing or replacement of marine ingredients that are good sources of high quality oils from shrimp feed formulation may result in EFAs deficiencies As we replace fish meal with alternative ingredients, for example soybean meal, we must ensure that we meet the shrimp EFAs requirements Lipid content and the associated C18 PUFA (poly unsaturated fatty acids), linoleic (18:2n-6) and linolenic (18:3n-3) acids, as well as n-3 and n-6HUFA (highly unsaturated fatty acids), eicosapentaenoic acid (EPA, 20:5n-3), docosahexaenoic acid (DHA, 22:6n-3) and arachidonic acid (ARA, 20:4n-6) are required in shrimp and other crustacean feeds at levels between and 10 g kg1 (Akiyama et al 1991; Gonz alez-Felix & Perez-Velazquez 2002) Generally, the primary protein and lipid sources used in practical shrimp feeds are fish meal and fish oil (Cheng et al 2002) Lim et al (1997) have reported that menhaden oil rich in n-3 HUFA (20:5n-3 and 22:6n-3) was better utilized by Penaeus vannamei than vegetable lipid sources such as linseed, sunflower, corn, soybean and coconut oil and stearic acid Samocha et al (2010) also suggested that the supplementation of HUFAs is a critical component to replace marine fish oil in shrimp feed Their results demonstrated that the complete replacement of fish meal and fish oil using non-marine ingredients can be accomplished using supplementation of plant oils with DHA- and ARA-rich oils from fermented products Other studies have reported that partial or total placement of fish meal and fish oil with soybean meal and soy oil had no adverse effect on shrimp growth performance (Davis & Arnold 2000; Samocha et al 2004; Gonzalez-Felix et al 2010), but shrimp body crude fat and cholesterol concentration were reduced (Cheng & Hardy 2004) According to Gonz alezFelix et al (2010), the substitution of fish oil up to 90% by plant-based oils in diets can be done without a significant reduction in growth performance, FCR, production yield and survival in L vannamei Apparently, this 10% of fish oil remaining in the diet supply enough of the essential fatty acids ARA, EPA and DHA for the proper development of this species, although the fatty acid composition of the muscular tissue of the animal reflected the lipid source fatty acid profile added to the diet followed by a reduction in HUFAs as fish oil was replaced High levels of n-3 fatty acids can be obtained with the use of linseed oil, most of it comprised of the PUFA a-linolenic acid; yet, the levels of the essential HUFAs in linseed oil are found at low levels Cholesterol is a vital component of cell membranes It is the precursor of bile acids, steroids, and moulting hormones (Cheng & Hardy 2004) It is reported to be an essential nutrient for growth and survival of shrimp (Kanazawa et al 1971; Gong et al 2000; Morris et al 2011) Gong et al (2000) suggested that dietary cholesterol requirement of L vannamei juveniles was affected by dietary phospholipids such as soybean lecithin and purified phosphatidylcholine Phospholipids are considered another dietary necessity for optimum shrimp growth Dietary cholesterol and phospholipids interact to improve growth as well as affect retention of total lipid and triglycerides in hepatopancreas and cholesterol in muscle of L vannamei juveniles Several studies have indicated a clear need for cholesterol supplementation in plant-based diets (Gong et al 2000; Morris et al 2011) Gong et al (2000) suggested that optimal growth of L vannamei was obtained with 3.5 g kg1, 1.4 g kg1, 1.3 g kg1 and 0.5 g kg1 supplemental cholesterol at dietary PL levels of 0, 15, 30 and 50 g kg1, respectively, in dietary treatments containing no fish meal Similar results reported by Morris et al (2011) demonstrated that the cholesterol supplements in dietary treatments formulated with no fish meal and targeted crude protein levels of 350 g kg1 for L vannamei were between 0.2 and 0.4 g kg1, thus containing a cholesterol level between 0.76 and 1.1 g kg1 of diet Shrimp are able to assimilate minerals directly from the aquatic environment (Montoya et al 2000) In shrimp, minerals serve as structural components of hard and soft tissues and metalloproteins as well as enzymatic cofactors and enzymatic activators (Davis & Lawrence 1997) Shrimp can utilize some soluble minerals such as calcium, copper, iron, magnesium, phosphorus, potassium, selenium, sodium and zinc from the water through the gill, epidermis or both Generally, phosphorus is found at low concentration in natural water relative to its requirement by phytoplankton (Boyd 2007) When fish meal is replaced by soybean meal, the first limiting mineral in shrimp feed formulation is phosphorus as only 3040% of total phosphorus content in soybean meal is available for L vannamei (Hertrampf & Piedad-Pascual 2000) Therefore, supplemental phosphorus is essential for optimal shrimp growth as fishmeal was removed The dietary phosphorus requirement for juvenile L vannamei ranges from 3.4 to 20 g kg1 (Davis et al 1993) and 20.9 22.0 g kg1 for postlarval L vannamei (Niu et al 2008) The dietary phosphorus requirement for shrimp is dependent on the calcium content in diet although a dietary calcium supplement is not required (Davis et al., 1993; Cheng et al 2006) Compared with fish meal, soybean meal is found to have low availability of selenium, 48.0% and 17.5%, respectively (Gabrielsen & Opstvedt 1980) Selenium is an essential trace element that functions as a component of the enzyme glutathione peroxidase in shrimp, but it can be toxic (Davis & Gatlin 1996; Wang et al 2006) Glutathione peroxidase converts hydrogen peroxide and lipid hydroperoxides into water and lipid alcohols, respectively, thus protecting the cell from the deleterious effects of peroxides (Davis & Gatlin 1996) Juvenile P vannaemi was found to grow best when fed semi-purified diets supplemented with 0.20.4 mg Se kg1 diet (Davis & Gatlin 1996) Supplemental selenium is not required in practical diets containing more than 150 g kg1 fish meal Therefore, selenium supplementation may be required in diets formulated with predominantly plant ingredients Due to potentially toxic effects, selenium supplementation of 0.1 mg kg1 is approved to be used with fish and crustaceans (Davis & Gatlin 1996) There are other issues of using soybean meal as an alternative to fishmeal besides nutritional factors such as the presence of nutrient inhibitors Raw soybean contains antinutritional factors such as trypsin inhibitors, lectins, oligosaccharides, antigens and saponins that may affect the digestion and reduce nutrient availability to shrimp (Dersjant-Li 2002) However, the effect of some of these antinutrients can be reduced by heat process (New 1987) Clearly, the use of soybean meal in shrimp feed is feasible However, there are several other plant protein sources that may be considered as alternative ingredients used in Aquaculture Nutrition 19; 441448 ê 2013 John Wiley & Sons Ltd association with soybean meal to balance nutritional composition in feed formulations when non-fishmeal diets are formulated It appears that fish meal can be partially or completely removed from shrimp formulations if suitable alternative sources of protein and lipids are provided to meet the nutritional requirements of the animal (Lim & Dominy 1990, 1992; Piedad-Pascual et al 1990; Sudaryono et al 1995; Cruz-Suarez et al 2001; Smith et al 2001; Davis et al., 2004; Samocha et al 2004; Amaya et al 2007a,b; Roy et al., 2009) Recently, National Research Council (NRC 2011) reported the minimum nutrient requirements for maximum performance of L vannamei (Table 3) Yet, there is still limited information available on amino acid requirement data for L.vannamei, as well as fatty acids, vitamins and minerals are highly digestible; therefore, the values presented represent nearly 100% bioavailability The use of complementary ingredients is a practice used to obtain a more balanced nutrient profile in the feeds (i.e essential amino acids, fatty acids, minerals) and to increase nutrient utilization and facilitate feed processing (Amaya et al 2007a) Sookying (2010) reported on a series of studies that demonstrated and developed a range of soy-based diets This includes diets that demonstrate that fish meal Table Nutrient requirements of L vannamei (dry matter basis) (from NRC 2011) Item Typical energy and protein concentrations Digestible energy (kcal kg1 diet) Digestible protein (g kg1) Amino acid (g kg1) Lysine Fatty acids (g kg1) n-3 LC-PUFA Cholesterol (g kg1) Macrominerals (g kg1) Magnesium Phosphorus Microminerals (mg kg1) Copper Selenium Zinc Fat-soluble vitamins A (mg kg1) E (mg kg1) Water-soluble vitamins (mg kg1) Vitamin B6 Vitamin C Minimum requirement for L vannamei 3000 300 16 2.55.0 g kg1 1.3 2.63.5 37 1632 0.20.4 15 1.4 100 80100 50100 These requirements have been determined with highly purified ingredients in which the nutrient composition has been defined Aquaculture Nutrition 19; 441448 ê 2013 John Wiley & Sons Ltd (100 g kg1 diet) could be totally removed from diets for L vannamei by a combination of plant and animal protein sources (soybean meal and poultry by-product meal) or all plant protein sources (soybean meal in combination with DDGS or pea meal with the inclusion of corn gluten meal and squid meal) when diets are formulated to contain acceptable nutrient levels and proper balanced nutrients without any apparent effect on survival, growth and feed palatability (Sookying & Davis 2011) They also demonstrated that up to 120 g kg1 soy protein concentrate could be used in a high soy diet under outdoor production conditions without an effect on production performance of the shrimp (Sookying & Davis 2012) Alternative feed formulations for the pacific white shrimp seem to work across a number of culture technologies (clear water research systems, outdoor tank systems and research ponds) as well as across a range of densities in outdoor ponds (Sookying et al 2011) Given the range of culture systems and densities, the use of alternative feed formulations for this species is warranted and appropriate for commercial production Akiyama, D.M (1989) Soybean meal utilization by marine shrimp In: Proceeding of the World Congress, Vegetable Protein Utilization in Human Foods and Animal Feedstuffs (Applewhite, T.H ed.), pp 252265 American Oil Chemists Society, Champaign, IL, USA Akiyama, D.M., Dominy, W.G & Lawrence, A.L (1991) Penaeid Shrimp Nutrition for the 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Substitution of full-fat soybeans for commercial soybean meal in diets for shrimp Penaeus vannamei J Appl.Aquacult., 1, 3546 Aquaculture Nutrition 19; 441448 ê 2013 John Wiley & Sons Ltd Lim, C., Ako, H., Brown, C.L & Hahn, K (1997) Growth response and fatty acid composition of juvenile Penaeus vannamei fed different sources of dietary lipid Aquaculture, 151, 143 153 Lim, C., Garcia, J.C., Yildirim-Aksoy, M., Klesius, P.H., Shoemaker, C.A & Evans, J.J (2007) Growth response and resistance to Streptococcus iniae of Nile tilapia, Oreochromis niloticus, fed diets containing distillers dried grains with solubles J World Aquaculture Soc., 38, 231237 Lim, C., Yildirim-Aksoy, M & Klesius, P.H (2009) Growth response and resistance to Edwardsiella ictaluri of channel catfish, Ictalurus punctatus, fed diets containing distillers dried grains with solubles J World Aquaculture Soc., 40, 182 193 Markey, J.C (2007) Replacement of poultry by-product meal in production diets for the Pacific white 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Cruz, E.M & Sumalangcay, A Jr (1990) Supplemental feeding of Penaeus monodon juveniles with diets containing various levels of defatted soybean meal Aquaculture, 89, 183191 Ray, A.J., Lewis, B.L., Browdy, C.L & Leffler, J.W (2009) Suspended solids removal to improve shrimp (Litopenaeus vannamei) production and an evaluation of a plant-based feed in minimalexchange, superintensive culture systems Aquaculture, 299, 89 98 Aquaculture Nutrition 19; 441448 ê 2013 John Wiley & Sons Ltd Reigh, R.C & Ellis, S.C (1992) Effects of dietary soybean and fish-protein ratios on growth and body composition of red drum (Sciaenops ocellatus) fed isonitrogenous diets Aquaculture, 104, 279292 Robinson, E.H & Li, M.H (2008) Replacement of soybean meal in channel catfish, Ictalurus punctatus, diets with cottonseed meal and distillers dried grains with solubles J World Aquaculture Soc., 39, 521527 Roy, L.A., Bordinhon, A., Sookying, D., Davis, D.A & Whitis, G.N (2009) Demonstration of alternative feeds for 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Internacional de Nutrici on Acucola 19-22 Noviembre, 2000 (Cruz -Suarez, L.E., Ricque-Marie, D., Tapia-Salazar, M., Olvera-Novoa, M.A & y Civera-Cerecedo, R eds), pp 277286 Merida, Yucatan, Mexico Sookying, D (2010) Development and application of soybean based diets for Pacific white shrimp Litopenaeus vannamei, Ph.D Dissertation Auburn University, Auburn, AL pp 141 Sookying, D & Davis, D.A (2011) Pond production of Pacific 408 white shrimp (Litopenaeus vannamei) fed high levels of soybean meal in various combinations Aquaculture, 319, 141149 Sookying, D & Davis, D.A (2012) Use of soy protein concentrate in practical diets for Pacific white shrimp (Litopenaeus vannamei) reared under field conditions Aquacult Int., 20, 357371 Sookying, D., Silva, F.S.D., Davis, D.A & Hanson, T (2011) Effects of stocking density on the performance of Pacific white shrimp Litopenaeus vannamei cultured under pond and outdoor tank conditions using a high soybean meal diet Aquaculture, 319, 231239 Stone, D.A.J., Hardy, R.W., Barrows, F.T & Cheng, Z.J (2005) Effects of extrusion on nutritional value of diets containing corn gluten meal and corn distillers dried grain for rainbow trout, Oncorhynchus mykiss J Appl.Aquacult., 17, 120 Sudaryono, A., Hoxey, M.J., Kailis, S.G & Evans, L.H (1995) Investigation of alternative protein sources in practical diets for juvenile shrimp, Penaeus monodon Aquaculture, 134, 313323 Tacon, A.G.J (1994) Feed Ingredients for Carnivorous Fish Species: Alternatives to Fishmeal and Other Fishery Resources, pp 39 FAO, Fisheries Circular No 881, Rome, Italy Tacon, A.G.J & Metian, M (2008) Global overview on the use of fish meal and fish oil in industrially compounded aquafeeds: trends and future prospects Aquaculture, 285, 146158 Thompson, K.R., Rawles, S.D., Metts, L.S., Smith, R.G., Wimsatt, A., Gannam, A.L., Twibell, R.G., Johnson, R.B., Brady, Y.J & Webster, C.D (2008) Digestibility of dry Matter, protein, lipid, and organic matter of two fish meals, two poultry by-product meals, soybean meal, and distillers dried grains with solubles in practical diets for sunshine bass, Morone chrysops x M saxatilis J World Aquaculture Soc., 39, 352363 Wang, W.-N., Wang, A.-L & Zhang, Y.-J (2006) Effect of dietary higher level of selenium and nitrite concentration on the cellular defence response of Penaeus vannamei Aquaculture, 256, 558 563 Watanabe, T (2002) Strategies for further development of aquatic feeds Fish Sci., 68, 242252 Webster, C.D., Tidwell, J.H & Yancey, D.H (1991) Evaluation of distillers grains with solubles as a protein source in diets for channel catfish Aquaculture, 96, 179190 Webster, D., Tidwell, J.H., Goodgame, L.S., Yancey, D.H & Mackey, L (1992) Use of soybean meal and distillers grains with solubles as partial or total replacement of fish meal in diets for channel catfish, Ictalurus punctatus Aquaculture, 106, 301309 Wu, Y.V., Rosati, R., Sessa, D.J & Brown, P (1994) Utilization of protein-rich ethanol co products from corn in tilapia feed J Am Oil Chem Soc., 71, 10411043 Aquaculture Nutrition 19; 441448 ê 2013 John Wiley & Sons Ltd Aquaculture Nutrition 2013 19; 449460 1,2 1 doi: 10.1111/j.1365-2095.2012.00976.x 1 Grupo de Investigacion en Acuicultura (IUSA & ICCM), University of Las Palmas de Gran Canaria, Telde, Gran Canaria, Espana; Oceanography Department, Faculty of Science, Alexandria University, Alexandria, Egypt; Dpto Biologa Aplicada, Escuela Politecnica Superior, Universidad de Almera, Almera, Espana The aim of the present study was to determine the optimum dietary levels of krill phospholipids (KPL) for sea bream (Sparus aurata) larvae, and its influence on larval development and digestive enzymes activity Larvae were fed five formulated microdiets with five different levels of KPL Complete replacement of live preys with the experimental microdiets for seabream larvae produced high survival and growth rates, particularly in fish fed the highest levels of KPL In the present study, increase in dietary KPL up to 120 g kg1 (100 g kg1 total PL) significantly improved larval survival and growth, whereas further increase did not improve those parameters An increase in alkaline phosphatase, trypsin and lipase activity with the elevation of KPL up to 120 g kg1 was also found denoting a better functioning of digestive system Besides, there was a linear substrate stimulatory effect of dietary KPL on phospholipase A2 activity Finally, increasing dietary KPL lead to better assimilation of n-3 HUFA especially eicosapentaenoic acid, reflected in the higher content of these fatty acids in both neutral and polar lipids of the larvae In summary, KPL were found to be an excellent source of lipids for seabream larvae Optimum inclusion levels of this ingredient in microdiets to completely substitute live preys at this larval age were found to be 120 g kg1 KPL KEY WORDS: alkaline phosphatase, fatty acids, krill phospholipids, phospholipase A2, sea bream larvae, trypsin Received 30 January 2012; accepted 18 June 2012 Correspondence: R Saleh, Grupo de Investigacion en Acuicultura (IUSA & ICCM), University of Las Palmas de Gran Canaria, Carretera de Taliarte, s/n, 35200 Telde, Gran Canaria, Espana and Oceanography Department, Faculty of Science, Alexandria University, 21515 Moharram Bek, Alexandria, Egypt E-mail: reda-saleh@hotmail.com ê 2012 John Wiley & Sons Ltd Dietary phospholipids (PL) improve culture performance of various freshwater and marine fish species (Izquierdo & Koven 2011), enhancing growth and survival, reducing morphological alterations in larvae (Kanazawa 1993; Salhi et al 1999; Izquierdo et al 2001; Kjứrsvik 2009) and early juveniles (Coutteau et al 1997), and increasing fish resistance to stress (Takeuchi et al 1992; Kanazawa 1993) Despite PL metabolic pathways, including those of de novo PL biosynthesis, are essentially the same in fish as in mammals (Caballero et al 2006b), the fish larvae and early juvenile have a limited capacity to synthesize de novo (Coutteau et al 1997; Salhi et al 1999) Thus, addition of PL to diets for fish larvae contributes to assimilation of dietary lipid by increasing the enteric lipoprotein synthesis (Liu et al 2002; Hadas et al 2003) and release in lamina propria, significantly reducing lipoprotein size by promoting VLDL synthesis (higher in PL), rather than chylomicron production (higher in NL) (Liu et al 2002; Caballero et al 2003, 2006b) Indeed, young fish receive abundant of PL during embryo and larval development either from yolk sac lipids or from wild preys (Rainuzzo et al 1997; Van Der Meeren et al 2008) Therefore, PL seems to be essential for the adequate growth and development of fish larvae Described phospholipid requirements are around 2040 g kg1 DW of diet for juvenile fish, and they may be higher in larval fish Frequently, those requirements have used plant PL such as soybean lecithin or egg yolk lecithin, whereas marine PL, rich in docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), have been more scarcely studied (Salhi et al 1999; Cahu et al 2003) DHA and EPA present in the PL fraction of larval diets seem to be more beneficial than in the NL fraction (Salhi et al 1999; Cahu et al 2003; Gisbert et al 2005; Wold et al 2007) Cahu et al (2003) carried out a doseresponse study with sea bass larvae, using five levels of phospholipids at a constant dietary lipid level (PL, 27116 g kg1 dw) They found that the diet with the highest dietary PL gave the best larval performance and lower skeletal malformation rates A similar result was found by Hamza et al (2008) for pikeperch larvae, which also showed best growth with the diet highest in PL (90 g kg1 of dry matter) The digestive system of larvae is not fully developed at first feeding The digestion of ingested food occurs in the larval intestine, where the pH remains alkaline and trypsinlike enzyme activity accounts for the proteolytic activity (Walford & Lam 1993) At first feeding, the pancreatic and intestinal enzyme activities are generally low (Cousin et al 1987) Digestive enzyme activity increase during the first 10 dph in Solea senegalensis (Ribeiro et al 1999), whereas an increase in alkaline phosphatase activity has been found to reflect the development of the brush border membranes of enterocytes in Atlantic cod (Gadus morhua) (Wold et al 2007) Moreover, the addition of dietary PL enhanced gut maturation index in this species, based on the relation between brush border alkaline phosphatase and cytosolic leucinealanine aminopeptidase Enhancement of gut maturation by dietary PL could be related with a higher intracellular availability of PL for cell membrane and cell organelles formation, as dietary PL promotes re-acylation of digested lipids, increasing intracellular PL availability for lipoprotein synthesis in gilthead seabream (Liu et al 2002; Caballero et al 2003) In sea bass larvae, the response of phospholipase A2 to dietary phospholipid content was gradual and showed a great modulation range in expression Also, amylase and alkaline phosphatase activities revealed a proper maturation of the digestive tract in the larvae fed the highest dietary phospholipid levels (Cahu et al 2003) On the basis of the few studies where single pure phospholipid species have been used, the rank order for efficacy appears to be phosphatidylcholine, phosphatidylinositol, phosphatidylethanolamine and phosphatidylserine (Izquierdo & Koven 2011) Several studies also suggested that the phospholipid effect was not attributed to a general enhanced emulsification and digestion of lipids The evidence rather led to the hypothesis that early developing stages of fish had impaired ability to transport dietary lipids away from the intestine possibly through limitations in lipoprotein synthesis Thus, dietary PL increases the efficiency of transport of dietary fatty acids and lipids from the gut to the rest of the body (Coutteau et al 1997; Fontagne et al 1998; Salhi et al 1999; Izquierdo et al 2001) However, despite the many studies available denoting the importance of dietary PL, few of them have intended to determine quantitative PL requirements testing diets with at least five different levels of this nutrient Recently, krill PL have been found to constitute a suitable phospholipid source in diets for larval gilthead seabream (Betancor et al 2012) Thus, the aim of the present study was to determine the optimum requirements of krill PL for gilthead sea bream (Sparus aurata) larvae, and its influence on larval production performance and digestive enzymes activity Gilthead seabream larvae were obtained from natural spawnings from Instituto Canario de Ciencias Marinas [Grupo de Investigacion en Acuicultura (GIA), Las Palmas de Gran Canaria, Spain] Larvae (5.4 mm total length, 120 lg dry body weight) previously fed rotifers (Brachinus plicatilis) enriched with DHA Protein Selcođ (INVE, Dendermond, Belgium) until 16 dph were randomly distributed in 15 experimental tanks at a density of 2100 larvae tank1 and fed one of the diets tested in triplicate All tanks (200 L fibreglass cylinder tanks with conical bottom and painted a light grey colour) were supplied with filtered seawater (37 g L1 salinity) at an increasing rate of 0.4 1.0 L min1 to assure good water quality during the entire trial Water entered from the tank bottom and exited from the top to ensure water renewal and maintain high water quality, which was tested daily and no deterioration was observed Water was continuously aerated (125 mL min1) attaining 6.1 mg L1 dissolved O2 Average water temperature and pH along the trial were 19.1 C and 7.85, respectively Photoperiod was kept at 12 h light/12 h dark, by fluorescent daylights, and the light intensity was kept at 1700 lux (digital Lux Tester YF-1065, Powertech Rentals, Osborne Park City, WA, Australia) Five experimental microdiets (pellet size < 250 lm) with increasing phospholipid contents were formulated using sardine oil (Agramar S.A.,Las Palmas City, Spain) and krill oil (Qrill, high PL, Aker BioMarine, Fjordalleen, Norway) as sources of triglycerides and PL, respectively Their formulation and proximate analysis are shown in Table The fatty acid content is shown in Tables 2, and The desired lipid content (about 210 g kg1 DW) was completed if necessary with a non-essential fatty acid source, oleic acid (Oleic acid; Merck, Darmstadt, Germany) The microdiets were prepared by mixing squid powder and water-soluble components, and then the lipids and fat-soluble vitamins and, finally, gelatine dissolved in warm water Aquaculture Nutrition 19; 449460 ê 2012 John Wiley & Sons Ltd meal as cassava (root and foliage) is known to contain cyanogenic glycosides (Phuc et al 2000), while the content of anti-nutritional factors in sweet potato leaf meal and duckweed meal is considered negligible (Iqbal 1999; Dongmeza et al 2009) However, the high AD value for DM, OM and energy in cassava leaf meal suggests that this was of minor importance It has been shown that the content of cyanogenic glycosides in fresh cassava leaves is reduced with more than 80% by sun-drying (Phuc & Lindberg 2001; Hue et al 2010) The present study showed high AD of CP for soybean meal in striped catfish fingerlings High CP digestibility of soybean meal has earlier been reported for Nile tilapia and hybrid catfish (Tram et al 2011), tra catfish (Hien et al 2009), channel catfish (Wilson & Poe 1985) and rainbow trout (Kaushik et al 1995) However, Phumee et al (2011) recently reported that juvenile striped catfish showed decreasing AD of DM and CP with increasing inclusion of soybean meal in the diet This could be due to disturbed gut function (Nordrum et al 2000) due to the presence of anti-nutritional factors and indicates that inclusion of soybean meal has to be restricted to avoid negative impact on fish performance Moreover, it highlights the potential risk of using alternative feed ingredients to replace fish meal without prior knowledge of their possible anti-nutritional properties The AD of CP in duckweed meal was high, while the values for broken rice, maize meal, sweet potato leaf meal and cassava leaf meal were markedly lower Duckweed (Lemna sp.) have a good amino acid profile and high mineral content (Mbagwu & Adeniji, 1988) and has successfully been used as feed ingredient for tilapia (Oreochromis niloticus) (Fasakin et al 1999) and for Thai silver barb, common carp (Cyprinus carpio) and indigenous catla (Catla catla) (Azim & Wahab 2003) A low digestibility of CP was reported for cassava leaf meal in Hybrid catfish and Nile tilapia (Tram et al 2011) However, Ng Keong & Wee (1989) reported that sun-dried cassava leaf meal supported high growth rates in Nile tilapia Sweet potato leaf meal is well utilized by pigs (An 2004; Nguyen et al 2012), and cassava leaf meal has successfully been used as feed resources for livestock (Phuc & Lindberg 2001; Hue et al 2010; Nguyen et al 2012), while data on fish seem to be lacking In general, the average AD of EAA was high for all dietary treatments and similar between diets, except for the diet with cassava leaf meal where the AD was reduced This suggests that striped catfish have limitation in its capacity to digest EAA in cassava leaf meal Low AD of individual EAA in cassava leaf meal has also been reported for Nile tilapia (Tram et al 2011) The AD of EAA in the test ingredients was variable, with the highest average AD of EAA in soybean meal (89.9%) and duckweed meal (82.6%), followed by broken rice (81.3%) The average AD of EAA in soybean meal was comparable with those reported in earlier studies with African catfish (Clarias gariepinus) (Balogun & Ologhobo 1989), Hybrid catfish (Tram et al 2011), channel catfish (Wilson et al 1981) and Tilapia (Guimaraes et al 2008a) In contrast, the lowest average AD of EAA was found in maize meal, cassava leaf meal and sweet potato leaf meal Low AD values for maize were also found in Nile tilapia (Guimaraes et al 2008b) and channel catfish (Wilson et al 1981) In general, the AD values of most individual EAA in the test ingredients were high compared with the AD values for EAA in common feed ingredients for channel catfish (Wilson et al 1981) Moreover, the AD values were much higher than those reported for plant protein fed to the carnivorous fish species dourado (Salminus brasiliensis) (Borghesi et al 2009) The apparent digestibility of dry matter, organic matter and energy was high for all test ingredients, except for duckweed meal This may limit the possibility of using duckweed as replacement for fish meal, despite high digestibility of protein and essential amino acids, if the lower energy digestibility cannot be compensated for in feed formulation Moreover, low apparent digestibility of protein and individual essential amino acids in cassava leaf meal and sweet potato leaf meal may also impose limitations in feed formulation for the possible replacement of fish meal The authors wish to thank the Sida/SAREC MEKARN (Mekong Basin Animal Research Network) project for funding the research and the PhD scholarship for Chau Thi Da The authors also wish to thank the laboratory staff of the National Institute of Animal Husbandry, Ministry of Agriculture and Rural Development, Vietnam, and Ms Nguyen Thi Thuy, Mr Huynh Thanh Phuong and Mr Le Van Kha, who are students of the Aquaculture Department of Faculty of Agriculture and Natural Resources of Aquaculture Nutrition 19; 619628 ê 2013 John Wiley & Sons Ltd An Giang University, Vietnam, for their support and assistance during this study An, L.V (2004) Sweet potato leaves for growing pigs: Biomass yield, digestion and nutritive value Doctors dissertation, Swedish University of Agricultural Sciences (SLU), Uppsala (ISBN 91-576-6750-0) Anderson, J., Capper, B & Bromage, N (1991) Measurement and prediction of digestible energy values in feedstuffs for the herbivorous fish tilapia (Oreochromis niloticus Linn.) 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Regional, Bangkok, Thailand, 365358 Stirling (1985) Chemical and biological methods of water analysis for aquaculturists, Institute of Aquaculture University of Stirling, Stirling, p 117 Tacon, A.G.J (2007) Meeting the feed supply challenges of aquaculture In: FAO Global trade conference on Aquaculture, 29-31 May 2007, Qingdao, China Food and Agriculture Organization of United Nations FAO, Fisheries Proceeding No Rome, Italy, p 117121 Tram, N.D.Q., Ngoan, L.D., Hung, L.T & Lindberg, J.E (2011) A comparative study on the apparent digestibility of selected feedstuffs in hybrid catfish (Clarias macrocephalus x Clarias gariepinus) and Nile tilapia (Oreochromis niloticus) Aquacult Nutr., 17, e636e643 Van Soest, P.J., Robertson, J.B & Lewis, B.A (1991) Method of dietary fiber, nutral detergent fiber, and nonstarch polysaccharides in relation to animal nutrition J Dairy Sci., 74, 35834597 Vazquez-Ortiz, F.A., Caire, G., Huguere-Ciapara, I & Hernandez, G (1995) High-performance liquid chromatographic determination of free amino acid in shrimp J Liq Chrom, 18, 2059 2068 Wilson, R.P & Poe, W.E (1985) Apparent digestible protein and energy coefficients of common feed ingredients for channel catfish Prog Fish-Cult.,, 47, 154158 Wilson, R.P., Robinson, E.H & Poe, W.E (1981) Apparent and true availability of amino acids from common feed ingredients for channel catfish J Nutr., 111, 923 Aquaculture Nutrition 19; 619628 ê 2013 John Wiley & Sons Ltd Aquaculture Nutrition 2013 19; 629640 doi: 10.1111/anu.12012 1 1 1 Nutrition Laboratory, Institute of Aquatic Economical Animals, School of Life Science, Sun Yat-sen University, Guangzhou, China; Evonik Industries AG, Hanau, Germany; Evonik Degussa (China) Co., Ltd., Beijing, Chaoyang District, China; South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou, China Different ration levels were used to determine the digestible methionine (DMet) and lysine (DLys) maintenance requirements and the utilization efficiencies for gain above maintenance for two different sizes of tilapia (20.7 and 165 g), by feeding a soybean mealbased diet Protein gain and amino acid (AA) gain (e.g methionine, Met; lysine, Lys; R2 = 0.98) were best-fit linear functions of DMet and DLys intake in both fish size classes Slopes of these regression lines showed that the DMet utilization efficiencies for growth were 0.76 and 0.55 for juvenile and adult fish, respectively The DMet maintenance requirements were 3.12 and 16.5 mg BW(kg)0.7 day1 for juvenile and adult fish, respectively The DLys utilization efficiencies for gain were 0.72 and 0.52, whereas the DLys maintenance requirements were 16.9 and 68.8 mg BW (kg)0.7 day1, for juvenile and adult fish, respectively These results suggested that there was an obvious difference in the maintenance requirements and utilization efficiencies for gain above maintenance for DMet and DLys in two different sizes of tilapia The AA maintenance needs increased as fish increased in size, being greater in adult fish than in juvenile; however, the AA utilization efficiencies for gain above maintenance decreased with the increment of fish size KEY WORDS: fish size, lysine utilization efficiency, maintenance requirement, methionine utilization efficiency, Oreochromis niloticus, ration levels Received 22 May 2012; accepted 10 October 2012 Correspondence: Y.-J Liu, Nutrition Laboratory, Institute of Aquatic Economical Animals, School of Life Science, Sun Yat-sen University, Guangzhou 510275, China E-mail: edls@mail.sysu.edu.cn ê 2013 John Wiley & Sons Ltd Tilapia, which is well adapted to enclosed waters, produces high yields and is one of the most important and extensively cultured fish species on the global scale Among tilapia species, Nile tilapia (Oreochromis niloticus) is popular among farmers due to the advantages including fast-growing rate, short feeding cycle, improved disease resistance, strong fertility and delicious taste Owing to the increasing demand for tilapia in recent years, both quantity and good quality of feed should be enhanced to meet the nutritional requirements of this highly valued fish species for optimal aquaculture Methionine (Met) and lysine (Lys) are the most limiting amino acids (IAA) in diets based on plant protein sources for fish Therefore, precise estimation of these two amino acid (AA) requirements is necessary to formulate efficient and low-cost diets Similar to other species of growing animals, these two AA requirement studies in tilapia mostly made use of doseresponse experiments and utilized graded supplementation of the crystalline AA under study (Mazid et al 1978; Jackson & Capper 1982; Jauncey et al 1983; Santiago 1985; Santiago & Lovell 1988; Odum & Ejike 1991; Gaber 1994; Fagbenro 2000; Furuya et al 2006; Nguyen 2007; Nguyen & Davis 2009; Bomfim et al 2010; Furuya et al 2012) However, several difficulties or disadvantages were expected because of the low dietary supply of the limiting AA under study needed to achieve significant response effects (Cowey 1992) by graded supplementation In addition, overdosing of individual AAs may deliver AA imbalances (Wilson 2003; Helland et al 2006) Given that in doseresponse experiments, growth was measured against dietary AA concentration, it remained unknown as to what degree of growth was the result of different metabolic efficiencies linked to variable AA intake or to the variations in AA intake per se (Hauler & Carter 2001b) Therefore, some authors have suggested that partitioning IAA requirements between maintenance and growth would give more insight into the metabolic use of these IAA (Hurwitz & Bornstein 1973; Hurwitz et al 1978, 1983; Cook 1991; Shearer 1995; Fournier et al 2002) The assumption of factorial approach was that the nutrients need in the growing fish was the sum of the requirement for maintenance and growth Maintenance needs were generally thought to be highly dependent on body size and temperature, thus were proportional to the metabolic body weight, while the needs for growth were governed by the amount and composition of the added weight gain (Kaushik 1998; Lupatsch & Kissil 1998; Lupatsch et al 1998, 2001a,b, 2003a,b; Bureau et al 2002; Lupatsch & Kissil 2005) The factorial approach had recently gained acceptance for the determination of IAA requirements in aquatic animals (Hauler & Carter 2001a; Fournier et al 2002; Abboudi et al 2006a,b, 2007; Rollin et al 2006; Helland et al 2010; Richard et al 2010; Grisdale-Helland et al 2011a,b; Hua 2011; NRC 2011) This approach allowed requirements to be estimated for animal differing in their productive state (Fuller 1994) and can be applied to a wide range of conditions (Shearer 1995) However, the main limitation in its application to fish was the paucity of data on the maintenance AA requirements and AA utilization efficiency for growth (Mambrini & Kaushik 1995; Mambrini & Seudre 1995; Rodehutscord et al 1997; Fournier et al 2002; Abboudi et al 2006a,b) The maintenance requirement was defined as the amount of an AA to be ingested by fish to maintain its N equilibrium, which meant that no net synthesis or net breakdown of body protein took place In animal production, maintenance need was a non-earning but indispensable need Only when the maintenance requirement was satisfied, then the extra nutrients were used for growth The maintenance needs were different among different species, which resulted in the different nutrient reality requirements of animals While data on protein and energy requirements for maintenance were available for a few freshwater (Kaushik et al 1981, 1991, 1995; Kaushik & Luquet 1984; Gatlin et al 1986; Kaushik & Gomes 1988; Ng & Hung 1995; Mambrini 1996) and marine species (Birkett 1969; Lupatsch & Kissil 1998; Lupatsch et al 1998; McGoogan & Gatlin 1998; Fournier et al 2002), data on the maintenance requirements for AA were few and mainly available for Atlantic salmon, Salmo salar L (Hauler & Carter 2001a,b; Abboudi et al 2006a,b, 2007; Rollin et al 2006; Hauler et al 2007; Bodin et al 2008; Helland et al 2010; Grisdale-Helland et al 2011b), rainbow trout, Oncorhynchus mykiss (Rodehutscord et al 1997; Fournier et al 2002; Encarnacáa`o et al 2004; Nang Thu et al 2007, 2008; Bodin et al 2008, 2009), turbot, Psetta maxima (Peres & Oliva-Teles 2008; Hua 2011), Atlantic cod, Gadus morhua L (Grisdale-Helland et al 2011a) and black tiger shrimp, Penaeus monodon (Richard et al 2010) In none of these aforementioned works, had the effect of fish size on the maintenance requirement and utilization efficiency for gain been determined However, it was possible that AA maintenance needs increased as the fish increased in size, as had been reported in pigs (Fuller 1994) The maintenance requirement and utilization efficiency for gain for individual AA in fish have been determined using diets with gradient levels of a deficient AA (Rodehutscord et al 1997; Hauler & Carter 2001a,b; Abboudi et al 2006a,b, 2007; Rollin et al 2006; Hauler et al 2007; Bodin et al 2008, 2009; Peres & Oliva-Teles 2008) Hauler et al (2007) reported that ration level did not affect the utilization efficiency for gain or the maintenance requirement of the deficient AA in Atlantic salmon, Salmo salar L., parr Furthermore, Helland et al (2010) determined the Lys maintenance requirement and utilization efficiency for gain in Atlantic salmon postsmolts fed a single diet at different ration levels, which was performed in ruminants for energy in the 1960s (Blaxter et al 1966) and starting in the 1970s (Huisman 1976) It was not a prerequisite with this method that the nutrient was deficient in diets, the requirements simply characterized how the consumed and/or digestible nutrient from the diet was utilized in the body Therefore, this study was aimed to establish the digestible Met (DMet) and digestible Lys (DLys) maintenance requirements and utilization efficiency for gain above maintenance in juvenile and adult tilapia (O niloticus), by feeding a soybean mealbased diet with increasing ration levels or a protein-free diet to apparent satiation The linear regression model was used In this study, two diets were formulated: the protein-free diet (PF), which was used to determine the AA losses of Aquaculture Nutrition 19; 629640 ê 2013 John Wiley & Sons Ltd fish in a normal feeding regime, and the 330 g kg1 crude protein containing diet (CP33; Table 1) The non-protein diet containing energy, vitamins and minerals was supplied to prevent any energy limitation and to ensure that the fish remained in positive energy balance Five feeding treatments [PF (apparent satiation); 2%, 4%, 6% and 8% of BW] for small fish (initial weight: 20.7 g, trail 1) and five feeding treatments [PF (apparent satiation); 1%, 1.6%, 2.2% and 2.8% of BW] for large fish (initial weight: 165 g, trail 2) were employed in this study Each treatment was in triplicate Eight hundred juvenile tilapias were purchased from a commercial hatchery (Panyu, China) and kept in six fibreglass tanks (500 L) for week acclimatization with commercial tilapia diet (obtained from Table Formulation and composition of the experimental diets (g or MJ kg1) Experimental diets Ingredients (g kg ) Soybean meal Cottonseed meal Canada rapeseed meal Wheat flour Microcrystalline cellulose Zeolite powder Corn starch Monocalcium phosphate Soy oil Soy lecithin Vitamin mixture1 Mineral mixture2 Choline chloride Y2O3 Vc Chemical Analysis (g kg1) Dry matter Crude protein Crude lipid Ash Gross energy (MJ kg1) Methionine Cystine Lysine PF CP33 180 30 682 40 35 10 10 10 909 9.9 6.4 14.8 76.6 15.1 250 220 220 236.9 20 20 10 10 10 0.1 0.5 0.4 0.3 0.1 947 6.9 337 3.0 24.9 1.3 78.6 8.0 17.8 0.9 5.36 0.06 5.85 0.02 16.8 0.02 Vitamin premix contains (IU or mg g1 of diet): vitamin A, 6000 IU; vitamin D3, 5600 IU; vitamin E, 0.04; vitamin K3, 10; vitamin B1, 9; vitamin B2, 18; vitamin B6, 12; vitamin B12, 0.04; vitamin C, 140; niacin, 70; biotin, 0.16; folic acid, 3.2; D-calcium pantothenate, 40 Mineral premix contains (mg g1 of diet): magnesium, 100; iron, 70; manganese, 13.3; iodine, 2.24; copper, 10.5; zinc, 56; selenium, 0.3; cobalt, 1.75 Aquaculture Nutrition 19; 629640 ê 2013 John Wiley & Sons Ltd Zhongshan Taishan Feed Co., Ltd Guangdong, China) Then, these fish were individually selected to minimize weight variance at the inception of the trial Fish were fed their respective diets twice daily at 9:00 am and 16:00 pm During the feeding trial, the fish were weighed every weeks and the amount of diet given was adjusted accordingly Any uneaten feed was collected by siphoning daily, dried and weighed to calculate feed intake Studies were conducted in two semi-closed indoor water recirculating systems each with 15 circular plastic tanks (100 L for small fish and 200 L for large fish) Each tank was covered by a net to prevent fish from jumping out Effluent water from each experiment tank drained through a 50-mm stand pipe and returned to the sump via gravity flow Approximately 510% of the effluent water was discarded each day and replaced with clean disinfected estuarine water from a reservoir system Water quality was monitored daily The fish were cultured indoors and subjected to a natural photoperiod During the experimental period, the water temperature, dissolved oxygen and pH ranged from 28 to 29 C, 6.0 6.5 mg L1, 7.07.2 U, respectively Total ammonia nitrogen was maintained 0.5 mg L1 During the final 14 days of feeding trials, faeces samples were collected from each size block using siphon method (Sklan et al 2004) Faeces from each tank were kept separate, freeze-dried and stored at 20 C before analysis Yttrium (III) oxide or acid-insoluble ash and nutrients were analysed in diets and faeces (ECOTEAM, University of the Sunshine Coast, Faculty of Science, Health & Education, SippyDowns, QLD, Australia) and apparent digestibility coefficients (ADCs) calculated using (Maynard & Loosli 1969):      %Idiet %Nfaeces ADCs %ị ẳ 100 100 %Ifaeces %Ndiet where I is the inert marker (e.g yttrium oxide, acidinsoluble ash) and N is the nutrient Unable to collect the faeces of fish fed with PF diet, the apparent energy digestibility of the fish was determined by acid-insoluble ash (Chinese Pharmacopoeia 2005) Acidinsoluble ash content was determined by the ignition of ash, which was washed by 25-mL diluted hydrochloric acid and then filtrated with ashless filter paper, in a muffle furnace at 550 C for 24 h At the beginning of the experiment, 10 fish were euthanized (MS-222 at 10 mg L1; Sigma, St Louis, MO, USA) at stocking and frozen ( 20 C) for whole-body composition analysis Similarly, at the termination of the 8-week feeding trial, approximately 24 h after the last feeding, all fish were counted and weighed, and 10 fish per tank were randomly selected, anaesthetized and measured of individual body length and weight and three for analysis of whole-body composition All samples were kept at 20 C before analyses Samples from the diets, faeces and fish were freeze-dried and then finely ground Crude protein, crude lipid, moisture, gross energy and crude ash in diets, faeces and whole body were determined by standard methods (AOAC 1995) Moisture was determined by oven-drying at 105 C until constant weight Crude protein (N 6.25) was determined by the Kjeldahl method after acid digestion using an Auto Kjeldahl System (FOSS KjeltecTM 2300 Analyzer Unit, Denmark) Crude lipid was determined by the ether-extraction method using a Soxtec System HT (Soxtec System HT6, Tecator, Sweden) Gross energy content was measured by combustion in a Parr bomb calorimeter using benzoic acid as the standard Ash content was determined by a muffle furnace at 550 C for 24 h AA concentrations in diets and whole body were determined using an automatic AA analyzer (Biochrom 30 Amino Acid Analyzer, England) equipped with a column for physiological fluid analysis by a professional laboratory The indexes for the assessment of growth performance were calculated as follows: BW1 BW0 ị Weight gain ẳ 100 ; BW0 where BW0 and BW1 are initial and final mean body weights per tanks, respectively Specific growth rate (SGR; % day1 ị ẳ 100 LnBW1 LnBW0 ị days fedị1 Protein retention efficiency (PRE) ẳ 100 protein gain protein intake: For the determination of the AA requirements for maintenance and utilization efficiency for growth above maintenance, the geometric body weights of the fish were scaled by metabolic weight exponents A scaling coefficient for AA had not been determined for tilapia, and a coefficient of 0.7 for the geometric body weights was chosen for these nutrients based on determinations in gilthead sea bream, European sea bass and white grouper (Lupatsch & Kissil 1998; Lupatsch et al 1998, 2001a,b; Lupatsch & Kissil 2005) Subsequently, intake and nutrient gain data were standardized by referring original data values to the metabolic body weight of 0.7 (e.g mg BW (kg)0.7 day1 or g BW (kg)0.7 day1) Results were presented as mean SEM of three replicates All data were subjected to one-way ANOVA using SPSS 11.5 When significant difference (P < 0.05) was found, a Duncans new multiple range test was used to rank the groups Linear models were iteratively fitted to growth and utilization data using GRAPHPAD Prism version for Windows (GRAPHPAD Software; San Diego, CA, USA, www.graphpad.com) Mortality was low ([...]... japonicus Aquaculture, 255, 201209 Zhou, Q.C., Wu, Z.H., Tan, B.P., Chi, S.Y & Yang, Q.H (2006) Optimal dietary methionine requirement for juvenile cobia (Rachycentron canadum) Aquaculture, 258, 551557 Zhou, Q.C., Wu, Z.H., Chi, S.Y & Yang, Q.H (2007) Dietary lysine requirement of juvenile cobia (Rachycentron canadum) Aquaculture, 273, 634640 Aquaculture Nutrition doi: 10.1111/j.1365-2095.2012.00980.x 2013. .. fish Aquaculture, 2 74, 375397 Walford, J & Lam, T.J (1993) Development of digestive tract and proteolytic enzyme activity in sea bass Lates calcarifer larvae and juveniles Aquaculture, 109, 187205 Wold, P.A., Hoehne-Reitan, K., Cahu, C.L., ZamboninoInfante, J.L., Rainuzzo, J & Kjứrsvik, E (2007) Phospholipids vs neutral lipids: effects on digestive enzymes in Atlantic cod (Gadus morhua) larvae Aquaculture, ... and body composition in Nile tilapia (Oreochromis niloticus L.) Aquacult Res., 34, 487500 West, L.G., Greger, J.L., White, A & Nonnamaker, B.J (1978) In vitro study on saponin-mineral complexation J Food Sci., 43, 13401343 Aquaculture Nutrition 19; 468474 ê 2012 John Wiley & Sons Ltd Aquaculture Nutrition 2013 19; 475482 doi: 10.1111/j.1365-2095.2012.00981.x 1 1 1 1 1 2 1 1... canadum Aquaculture, 193, 8189 Chou, R.L., Her, B.Y., Su, M.S., Wang, G., Wu, Y.H & Chen, H.Y (2004) Substituting fishmeal with soybean meal in diets of juvenile cobia Rachycentron canadum Aquaculture, 229, 325333 Craig, S.R., Schwarz, M.H & McLean, E (2006) Juvenile cobia (Rachycentron canadum) can utilize a wide range of protein and lipid levels without impacts on production characteristics Aquaculture, ... Huang, T.S., Tsai, W.S., Hsueh, C.M., Chang, S.L & Leano, E.M (2004) Cobia culture in Taiwan: current status and problems Aquaculture, 237, 155165 Lin, Y.H., Lin, S.M & Shiau, S.Y (2008) Dietary manganese requirements of juvenile tilapia, Oreochromis niloticus 9 O aureus Aquaculture, 2 84, 207210 Liu, K., Wang, X.J., Ai, Q.H., Mai, K.S & Zhang, W.B (2010) Dietary selenium requirement for juvenile cobia,... acid composition and histology of rainbow trout, Oncorhynchus mykiss Aquaculture, 2 14, 253271 Caballero, M.J., Izquierdo, M.S., Kjứrsvik, E., Montero, D., Socorro, J., Fernandez, A.J & Rosenlund, G (2003) Morphological aspects of intestinal cells from gilthead seabream (Sparus aurata) fed diets containing different lipid sources Aquaculture, 225, 325340 Caballero, M.J., Gallardo, G., Robaina, L., Montero,... system for the continuous determination of metabolic rates of fish In: Measures for Success: Metrology and Instrumentation in Aquaculture Management (Kestemont, P., Muir, J., Sevilla, F & Wilot, P eds), Paper presented at the International Conference Bordeaux Aquaculture 19 94, Antony, France Cemagref Edition pp 167171 Focken, U., Becker, K & Lawrence, P (1997) A note on the effects of L-carnitine on... C.L (1999) High dietary lipid levels enhance digestive tract maturation and improve Dicentrarchus labrax larval development J Nutr., 129, 1195 1200 Aquaculture Nutrition 19; 449460 ê 2012 John Wiley & Sons Ltd Aquaculture Nutrition 2013 19; 461467 doi: 10.1111/j.1365-2095.2012.00979.x 1,2 1 1 1 1 2 2 The Key Laboratory of Mariculture, Ministry of Education, Ocean University of... highly prized (Chou et al 2004) Excellent flesh quality, rapid growth and adaptability to culture conditions confer highly desirable characteristics for global commercial aquaculture on cobia (Holt et al 2007) Following successful aquaculture development in Taiwan of China (Liao et al 2004), cobia is extensively farmed in cages in China, Vietnam and Philippines Recently, its production has been initiated... crustacean larviculture Aquaculture, 155, 149164 Folch, J., Lees, M & Stanley, G.H.S (1957) A simple method for the isolation and purification of total lipids from animal tissues J Biol Chem., 226, 497509 Fontagne, S., Geurden, I., Escaffre, A.M & Bergot, P (1998) Histological changes induced by dietary phospholipids in intestine and liver of common carp (Cyprinus carpio L.) larvae Aquaculture, 161, 213223