The use of algae in fish feeds as alternatives to fishmeal
Fishmeal is very extensively used in feeds for fish as well as other animals. A recent global survey estimated aquaculture consumption of fishmeal at 3724 thousand tonnes in 2006 (Tacon and Metian 2008). Now it is becoming increasingly evident that such continued exploitation of this natural resource will ultimately become both environmentally and economically unsustainable.
September | October 2012 The use of algae in fish feeds as alternatives to fishmeal International Aquafeed is published five 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 of information published. ©Copyright 2012 Perendale Publishers Ltd. All rights reserved. No part of this publication may be reproduced in any form or by any means without prior permission of the copyright owner. Printed by Perendale Publishers Ltd. ISSN: 1464-0058 The International magazine for the aquaculture feed industry FEATURE The use of algae in fish feeds as alternatives to fishmeal by Eric C. Henry PhD, Research Scientist, Reed Mariculture Inc., USA F ishmeal is very extensively used from consideration. This reflects the very methionine, threonine, and tryptophan (Li in feeds for fish as well as other early evolutionary divergence of different algal et al. 2009), whereas analyses of the amino animals. A recent global survey groups in the history of life on earth. Only one acid content of numerous algae have estimated aquaculture consumption of the many algal groups, the Green Algae, found that although there is significant of fishmeal at 3724 thousand tonnes in produced a line of descent that eventually variation, they generally contain all the 2006 (Tacon and Metian 2008). Now it is gave rise to all the land plants. Therefore it can essential amino acids. For example, surveys becoming increasingly evident that such con- be difficult to make meaningful generalisations of 19 tropical seaweeds (Lourenço et al. tinued exploitation of this natural resource about the nutritional value of this extremely 2002) and 34 edible seaweed products will ultimately become both environmentally diverse group of organisms; rather it is neces- (Dawczynski et al. 2007) found that all and economically unsustainable. sary to consider the particular qualities of species analysed contained all the essential specific algae. amino acids, and these findings are consist- Any satisfactory alternative feed ingre- ent with other seaweed analyses (Rosell dients must be able to supply compara- Protein and amino acids and Srivastava 1985, Wong and Peter ble nutritional value at competitive cost. Fishmeal is so widely used in feeds 2000, Ortiz et al. 2006). Conventional land-based crops, especially largely thanks to its substantial content Analyses of microalgae have found similar grains and oilseeds, have been favoured of high-quality proteins, containing all the high contents of essential amino acids, as alternatives due to their low costs, and have essential amino acids. A critical shortcom- exemplified by a comprehensive study of proved successful for some applications ing of the crop plant proteins commonly 40 species of microalgae from seven algal when they were used as substitutes for used in fish feeds is that they are deficient classes that found that, “All species had similar a portion of the fishmeal. But even when in certain amino acids such as lysine, amino acid composition, and were rich in the these plant-based substitutes essential amino acids” (Brown can support good growth they et al. 1997). table 1: nutritional profiles of rotifers enriched using optimized protocols can cause significant changes in based on culture using reed Mariculture rotiGrow Plus® and enriched with the nutritional quality of the fish n-rich® feeds Taurine produced. One often-overlooked n-rich® feed type High Pro® Pl Plus® Ultra Pl® nutrient is the non-protein Why algae? Moderate sulphonic acid taurine, which The reader may wonder why PUFa; overnight extreme is sometimes lumped with algae, including both macroalgae applications overnight or 2-6 hr DHa 2 hr amino acids in discussions gut-load enrichment enrichment (‘seaweeds’) and microalgae (e.g. of nutrition. Taurine is usu- maintenance phytoplankton), and which are ally an essential nutrient for popularly thought of as ‘plants’, Composition of Biomass carnivorous animals, including would be good candidates to some fish, but it is not found serve as alternatives to fishmeal lipid (Dry wt. % of Biomass) 35% 44% 66% in any land plants. However, in fish feeds. One fundamental DHa (% of lipids) 37% 41% 44% although taurine has been consideration is that algae are much less often investigat- the base of the aquatic food ePa 5% 2% 0.5% ed than amino acids, it has chains that produce the food been reported in significant ara 1.0% 1.0% 1.2% resources that fish are adapt- quantities in macroalgae such ed to consume. But often it is total PUFas 45% 45% 48% as Laminaria, Undaria, and not appreciated that the bio- Porphyra (Dawczynski et al. Protein 38% 32% 18% chemical diversity among differ- 2007, Murata and Nakazoe ent algae can be vastly greater Carbohydrate 19% 15% 7% 2001) as well as certain than among land plants, even microalgae, for example the when ‘Blue-Green Algae’ (e.g. ash 8% 9% 10% green flagellate Tetraselmis Spirulina), more properly called Dry weight Biomass 9% 9% 9% (Al-Amoudia and Flynn Cyanobacteria, are excluded 1989), the red unicellular alga 10 | InternatIOnal AquAFeed | September-October 2012 FEATURE Porphyridium (Flynn and Flynn 1992), the dino- Macroalgae (seaweeds) of many kinds can form flagellate Oxyrrhis (Flynn and Fielder 1989), extensive stands with high biomass density and the diatom Nitzschia (Jackson et al. 1992). Pigments A few algae are used as sources of pig- ments in fish feeds. Haematococcus is used to produce astaxanthin, which is responsible for the pink colour of the flesh of salmon. Spirulina is used as a source of other carotenoids that fishes such as ornamental koi can convert to astaxanthin and other brightly coloured pig- ments. Dunaliella produces large amounts of beta-carotene. Lipids In addition to its high content of high- quality protein, fishmeal provides lipids rich in ‘PUFAs’, or polyunsaturated omega-3 and omega-6 fatty acids. These are the ‘fish oil’ lipids that have become highly prized for their contribution to good cardiovascular health in humans. But it is not always appreciated that algae at the base of the aquatic food chain in fact originate these ‘fish oil’ fatty acids. These desirable algal fatty acids are passed up the acid (EPA), docosahexaenoic acid (DHA), for production of zooplankton necessary food chain to fish, and they are indeed essen- and arachidonic acid (ARA). There is a for the first feeding of larval fish, as well as tial nutrients for many fish. substantial literature devoted to analysis filter-feeding shellfish. Algae have been recognised as an of the PUFA content of microalgae, par- Many shellfish producers are aware obvious alternative source of these ‘fish ticularly those used in aquaculture, because the sterol profile of feed lipids is of criti- oil’ fatty acids for use in fish feeds (Miller they have long been recognised as the cal importance, but much less attention et al. 2008), especially eicosapentaenoic best source of these essential nutrients has been paid to the importance of the Your challenge is our passion. MetAMINO® – The superior methionine source for your aquafeed. www.evonik.com/feed-additives | email@example.com September-October 2012 | InternatIOnal AquAFeed | 11 WHO CARES... …If profits in the aquaculture industry are as appetising as a salmon dinner? As feed prices soar and formulation moves towards sustainability, aquaculture producers must think differently to stay on the menu. In all phases of the fish’s life, proper nutrition will improve health. 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To find out more, visit www.buhlergroup.com Bühler AG, Feed & Biomass, CH-9240 Uzwil, Switzerland, T +41 71 955 11 11, F +41 71 955 28 96 firstname.lastname@example.org, www.buhlergroup.com Innovations for a better world. FEATURE Various species of microalgae are used as Ulva fed to European Sea Bass (Valente aquaculture feeds, depending on the cell size and et al. 2006); Ulva fed to Striped Mullet nutritional profile needed for particular applications (Wassef et al. 2001); Ulva or Pterocladia fed to Gilthead Sea Bream (Wassef et al. 2005); Porphyra, or a Nannochloropsis- Isochrysis combination fed to Atlantic Cod (Walker et al. 2009, 2010). Unfortunately, it has rarely been possible to determine the particular nutritional factors respon- sible for these beneficial effects, either because no attempt was made to do so, or poor design of the study. For example, in one of the few studies that has focused on the effects of substi- tuting algal protein for gluten protein, the control and all the test diets contained casein plus added methionine and lysine, no analysis of the algal protein was provided, and the algal protein (a biofuel process by-product) contained very high levels of aluminium and iron (Hussein et al. 2012). More and better-designed studies are necessary before we will have sterol profile of fish feeds. Aside from It is not surprising that the biochemical a good understanding of how algae can best alterations in the normal sterol profile of compositions of certain marine micro- be used in fish feeds. the fish, the possible endocrine effects of algae are well-matched to the nutritional plant phytosterols in fish feeds (e.g. soy requirements some marine fish. Larval Choosing the right algae phytohormones) have yet to be thor- feeds are probably deserving of the most Often the algae chosen for fish feeding oughly investigated (Pickova and Mørkøre attention in efforts to discover how algae studies appear to have been selected largely 2007). can best be used in fish feeds, because for convenience, because they are low-cost microalgae are a natural component of and commercially available. For example, Use of algae in aquaculture the diet of many larval fish, either con- microalgae such as Spirulina, Chlorella and Many different algae already play a vital sumed directly or acquired from the gut Dunaliella can be produced by low-cost open- role in aquaculture. It is widely known that contents of prey species such as rotifers pond technologies and are marketed as dry the addition of microalgae to larval fish and copepods. Existing protocols that use powders, and their nutritional profiles are well-documented. Macroalgae such as the ‘kelps’ Laminaria, Undaria, and Durvillea, table 2: Because these algae are produced using continuous-harvest technology that maintains exponential growth, their protein and lipid contents are comparable to those provided by fish feeds. and the brown rockweed Ascophyllum, occur in dense stands that can be har- nannochloropsis tetraselmis sp. Pavlova sp. Isochrysis thalassiosira vested economically, and they have a long (Dry Weight) oculata (t-Iso) weissflogii history of use as sources of iodine, as soil amendments, and animal feed additives to supply trace elements. Protein 52% 55% 52% 47% 52% In recent years there has been great Carbohydrate 16% 18% 23% 24% 23% interest in the potential of algae as a biofuel feedstock, and it has often been lipid 17% 14% 20% 17% 14% proposed that the protein portion remain- ing after lipid extraction might be a useful culture tanks confers a number of benefits, microalgae to improve the PUFA profile input for animal feeds (e.g. Chen et al. 2010). such as preventing bumping against the walls of live prey (Table 1) demonstrate how However, the algae chosen for biofuel produc- of the tanks (Battaglene and Cobcroft 2007), effectively an algal feed can enhance the tion may not be optimal for use as a feed input, enhancing predation on zooplankton (Rocha nutritional value of these live feeds. and the economic pressure for the lowest-cost et al. 2008), enhancing the nutritional value of methods of fuel production is likely to result zooplankton (Van Der Meeren et al. 2007), Use of algae in in protein residues with contamination that as well as improving larval digestive (Cahu et formulated fish feeds makes them unfit for use as feed (e.g. Hussein al. 1998) and immune (Spolaorea et al. 2006) Various species of macroalgae and micro- et al. 2012). functions. algae have been incorporated into fish feed By contrast, the high-value microalgae that are Furthermore, it has also been shown formulations to assess their nutritional value, used in shellfish and finfish hatcheries are generally that larvae of some fishes benefit greatly and many have been shown to be beneficial: produced in closed culture systems to exclude by direct ingestion of microalgae (Reitan Chlorella or Scenedesmus fed to Tilapia (Tartiel contaminating organisms, and they cannot be et al. 1997). One study has even shown et al. 2008); Chlorella fed to Korean rockfish dried before use without adversely affecting their that that live zooplankton could be elimi- (Bai et al. 2001); Undaria or Ascophyllum fed nutritional and physical properties, greatly reduc- nated from the larval diet of Red Drum if to Sea Bream (Yone et al. 1986); Ascophyllum, ing their value as feeds. Inevitably their production microalgae were fed along with a formu- Porphyra, Spirulina, or Ulva fed to Sea Bream costs are higher, but their exceptional nutritional lated microparticulate diet (Lazo et al.). (Mustafa and Nakagawa 1995); Gracilaria or value justifies the extra expense. Table 2 presents 12 | InternatIOnal AquAFeed | September-October 2012 FEATURE take your production to the TOP of the aquafOOd chain. Many leading aquafeed manufacturers in the industry count on Extru-Tech to engineer the perfect aquafeed production solution. Industry leading equipment and engineered production advantages will give you the upper hand over the competition. Could typical nutritional profiles of algae produced by er ties of numer- you use a cost effective improvement in Reed Mariculture Inc. ous algae will be performance and finished product quality? Just as it would be senseless to arbitrarily necessary in order substitute one conventional crop plant for to optimally exploit Contact one of the aquafeed Consultants another (e.g. potatoes for soybeans) when the great potential at extru-tech today at 785-284-2153. formulating a feed, the particular attributes offered by this of each alga must be carefully considered. diverse group of In addition to the protein/amino acid profile, organisms. But it is lipid/PUFA/sterol profile, and pigment content, already apparent there are important additional considerations. that algae will play The type and quantity of extracellular an impor tant part polysaccharides, which are very abundant in cer- in the effor t to tain algae, can interfere with nutrient absorption, move the formula- or conversely be useful binding agents in forming tion of fish feed feed pellets. The thick cell walls of microalgae “down the food such as Chlorella can prevent absorption of the chain” to a more nutritional value of the cell contents. Inhibitory sustainable future. compounds such as the phenolics produced ■ by some kelps, and brominated compounds References available produced by red algae such as Laurencia, can on request render an alga with an excellent nutritional analy- sis unsuitable for use in a feed. Depending on growth and process- Corporate offiCe ing conditions, algae More inforMation: P.O. Box 8 • 100 Airport Road can contain high con- Eric C. Henry PhD, Reed Mariculture Inc. Sabetha, KS 66534, USA centrations of trace Tel: +1 408 426 5456 Phone: 785-284-2153 ® Fax: +1 408 377 3498 Fax: 785-284-3143 elements that may be Email: email@example.com firstname.lastname@example.org detrimental. Website: www.reedmariculture.com www.extru-techinc.com Fur ther careful study of the prop- September-October 2012 | InternatIOnal AquAFeed | 13 ET-221A.indd 1 1/20/12 1:57 PM This igital e-print s art f he eptember ctober 012 dition f nternational d r i p o t S |O 2 e o I LINKS Aquafeed magazine. Content from the magazine is available to view free-of-charge, both as a full online magazine on our website, and as an archive of individual features on the docstoc website. Please click here to view our other publications on www.docstoc.com. 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