The use of algae in fish feeds as alternatives to fishmeal

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					                     September | October 2012
The use of algae in fish feeds as alternatives
                to fishmeal

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The International magazine for the aquaculture feed industry

                                                                   The use of algae in fish feeds
                                                                     as alternatives to fishmeal
                                                                                by Eric C. Henry PhD, Research Scientist, Reed Mariculture Inc., USA

          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-
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

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).

    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	

     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	

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 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

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                                                                                                        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:                                                    
detrimental.                     Website:                                                   
   Fur ther	 careful	
study	 of	 the	 prop-

                                                     September-October 2012 | InternatIOnal AquAFeed | 13
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Description: 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.