Chapter 8. Protein Feedstuffs Originating from Soybeans. Paul B. Brown. Sadasivam J. Kaushik. Helena Peres. INTRODUC1'lON. The soybean (Glycine sp.) ...
Chapter 8
Protein Feedstuffs Originating from Soybeans Paul B. Brown Sadasivam J. Kaushik Helena Peres
INTRODUC1'lON The soybean (Glycine sp.) is a leguminous plant native to Asia that has been introducee! to every non polar continent. Agricultural production of soybean seeds was thelargest global oilseed crop in 2003 (J'able 8.1; United Nations, Food ane! Agriculture Organization, 2004 database). Soybean secds are c1assified as an oilseed because of the relatively high concentration of 1ipid. Oilsceds can be uscd as is, al50 known as fuU-fat, or after lipie! extraction. Lipid is extracted trom oilseeds by a variety of methods, most often soIvent extraction, and the remaining cake can be further proccsscd iuto various meals for use in human or animal foods. In 2003, a significant portion of global soybean production was lIscel for extraction of oil rcsulting in a rclatively large global supply of high-protein soybean cake (Table 8.1). The global supply of soybean cake is approximately 65 percent of the total soybean production. Rapeseed and safflowcr cakes arc approximatcly 49 and 43 percent, respectively, of total soybean production, other perccntages are less. Altemative Protein Sources in Aquaculture Diets It) 2008 by The Haworth Press, Taylor & Francis Group. Ali rights reservcd. doi:1O.JJOO/5892~08
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206
ALTERNATIVE PROTEIN SOl/Re'ES fi\' A(){!ACULTU1ΠDIETS
TABLE 8.1. Global harvest of some oilseed crops in 2003 and volume of pro· cessed products (cakes) after extraction of oils (melric tons),a
Crop
Total harvest
Cake
Soybeans
189,523,638
123,327,242
Oil, palm fruit
139,148,600
3,727,703
Seed cotton
56,969,044
12,388,472
Coconuts
50,227,217
1,902,410
Ground nuts in sheU
37,057,652
7,416,247
Rapeseed
35,931,652
17,760,805
Sunflower
26,085,901
9,267,370
Drybeans
18,886,344
N/A
b
Sesame
2,765,419
736,057
Unseed
2,054,195
861,863
Lupins
1,596,444
NIA
Castor beans
1,153,768
NIA
Safflower
731,425
318,700
aValues tram United Nations Food and Agriculture (htlp:llfaostaUao.org/). bData
not available,
NUTRITIONAL CONCENTRA 110NS After barvesting, the raw soybean can be processed into a variety of products (Figure 8.1). The mast commonly used products in aquaculture are the toasted soybean mcals (SBM). Two forms are commonly available, dehulled (dh) soybean meal (usua! protein content of ~49 percent, as is basis), and a product in which the hulls have bcen added back to the toastecl meal rcsulting in a lowcr protein concentration (~44 percent, as is basis). For the remaindcr of this document, SBM will indicate the dehulled, soIvent-extracted toastcd soybean mca!. Raw soybean seeds, soy f1ours, soybean meals, protein concentrates, and protein isolates have been evaluated in a varicty of animal species. There arc limitations on use of raw soybeans in dicts fcd to aquatic animais because of the antinutritional factors (ANF) present in seeds. Exposing the seeds to heat treatment diminishes the concentrations of ANF. Heated soybean seeds can be classified into two categories,
Proleill Feedsll{ff::' Origillatillgj(om SoyfJertlls
207
Raw soybeans Clean, crack, dehull, condition, and f1ake
1 1
Full-fat flakes
Solvent extraction - - - -
1
~
Crude oil 1
Delatted soy flakes
Reflned oil
Lecilhin
~~~~1~'~~~1 Grindlng
l
Soy Ilours
Toastjng
l 1 l
S.oybean meal, dh
Soluble carbohydrate extraction
l
Say proteln concentrates
Protein extraction
l
Soy protein iso!ptes
Hulls added
Soybean meal
FIGURE 8.1. Schematic representalion of soybean processing resulling in soy flours and meal, protein concentrates, protein isolales, ail, and lecithin.
depending on the temperatllre used for heating. Hcatecl scecls are typically exposcd to temperatures of 225°F (l07°C), roasted seeds are exposed to higher temperatures and exposed for a longer period oftime. Temperatures lISCel for roasting can be as high as 400°F (2ü4°C), but the most commonly lIsed is arounel 30ü°F (149°C). Heating or roasting can improve utility of full-fat soybeans in diets fcd to sorne species. Protcin concentrates and isolates are more expensive than SBM .because of the additional processing steps. Expected macronutrient concentrations are presented in Table 8.2 for varions soybean prodncts. Agronomists cIassify soybeans as oilseeds, but nutritionists consider soybean sceds as high lipicl and high protein fcedstuffs. Artel'
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ALTERNA l'lVE l'IWTE/IV SOUl?CES /N il QUA CULTURE DlE1:')
TABLE 8.2. Expected macronulrient concentrations in heated soybean seeds, soybean meal (SBM), soy concentrate, and say isolate compared to a standard fÎsh meal (%, dry matter basis).
Macronutrient CtUde proteîn Crude fat Crude fiber
d
Ash
NFe
5eeds, heated a
58M a
b
Concentrate
Isolateb
Fish meala,c 78.3
42.2
53.9
65·72
90-92
20.0
1.1
0.5-1.0
05-1.0
9.1
5.5
4.3
3.5-5.0
0.1-0.2
0.6
5.0
5.4
4.0-6.5
4.0-5.0
11.3
27.3
35.3
20-22
3.0-4.0
0.7
8Values fram NRC (1994). bValues fram Endres (2001). cHerring fish meal. dN
x 6.25.
8Nitrogen-free 8xtract, calculated by difference.
lipid extraction, the resulting mcal is clearly a protein feedstuff. As soybean products are processed iuto mcals, concentrates, and isolates, the crude protein concentrations approach and exceed those values round in standard fish meals. However, the crllde fat and ash concentrations of aIl solvent-extracted soy products are lower than values round in fish meals, but the crude fiber and nitrogen-l'ree extract concentrations are higher than in fish meals. The differences in energyyielding macronutrients (fat and carbohydrate) are problematic in diets l'ccl to some species of fish. Lower ash, and therefore minerai concentrations, can be overcome by addition of rel ativel y Inexpensive inorganic mÎnerals. The fiber concentratÎons in soy products are not high enough to warrant concern in most dietary formulations. Each of the macronutrÎents can be fmther subdivicled into their constituent components. Concentrations of the ten essential amino acids plus cystine and tyrosine ln soybean sceds, meals, concentrates, and isolates m:e presented in Table 8.3 and compared to herring tÏsh meaL Concentrations of aIl amino acicls presented are lower in SBM than in fish meal with the exception of cystine. Of particular collcern are lysine, methionine, and
l'rolein Feedsl1!f/.i OrigillalÎflg/iolll Soyhewis
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TABLE 8.3. Amino acid concentrations of heated soybean seeds, saybean meal (SBM), say concentrate. and say isolate Gompared ta a standard fish meal (%, dry malter basis).a Aminoacid
Seeds, heated
SBM
Concentrate
Isolate
Fish meal b 4.3
Arginine
2.9
3.9
6.4
7.5
Histidine
1.1
1.4
2.0
2.4
1.6
Isoleucine
1.8
2.4
3.7
4.6
3.1
Leucine
3.1
4.2
5.9
7.2
5.6
Lysine
2.5
3.3
4.7
5.7
5.9
Methionine
0.6
0.7
1.0
1.1
Cystine
0.6
0.8
1.1
1.3
2.2 0.7 2.9
Phenylalanine
2.0
2.6
3.8
4.7
Tyrosine
1.5
2.2
2.8
3.4
2.3
Threonine
1.6
2.1
3.1
3.2
Tryptophan
0.5
0.8
1.0
3.4 1.2
0.8
Valine
1.9
2.5
3.8
4.6
3.7
"Values tram NRC (1998). bHerring fish meaL
threonine. The lysine concentration is 56 percent of the concentration found in herring tish meal, the concentration of methionine is 32 percent of the concentration in fish meal, and the lhreonine concentration is 66 percent of the value reporled for fish meal. These three essential amino acicls tend to be limiting in soy-basecl diets l'cd to aquatic animaIs. Dietary cystine can spare approximately 50 percent of the dietary methionine requirement in fish (Harding et al., 1977; Moon and Gatlin, 1991; Griffin et aL, 1994; Twibell et aL, 2000) and a more appropriate comparison would be the total values for melhionine plus cystine (total sulfur amino acid concentrations). Adding both values and expressing those as a functioll of the values in fish meal yiclds a comparative value of 52 percent of the total sulfur amino acid concentration in SBM compared to hCITingfish men1. As soy protein is further purified by processing inta soy concentrates, the amino acid concentrations increase. In a typical soy concentrate, the lysine concentration is 85 percent of the concentration found in herring fish meal, the
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1/,TEWVA TlVE r'ROTEIN SOURCES IN A(W;\ CULTURE DIETS
total sul fuI' amino acîcl concentrations are 95 percent of the values in fish meal and the threonine concentration is higher than that in fish meal. Arnino acid concentrations in soy isolates are higher than those in tlsh meal with the exception of lysine (5.7 percent in soy isolate5 compareel to 5.9 percent in herring fish l11eal) . . The lipiel fraction (crude fat) of soy is a consideration only in the full-fat heatecl seecls (Lim and Akiyama, 1992). Ct1lde soybean oi! COI1tains 12.2 percent palmitic acid (16:0),26.0 percent olck aciel (18: 1n9), 51.5 percent linoleic acid (18: 2n-6), and 7.0 percent linolenic acid (l8:3n-3) (expressecl as a percentagc of the total fatty aciels; NRC, 1994). A fuU -fat heateel seeclmeal contains 10.3 percent 18:2n-6 and lA percent 18:3n-3 (expressed as percentage of the dry meal). The essential fatty acids of fishes arc the n-6 ancll1-3 families and range from 0.5 to 1.7 percent of the diet (NRC, 1993). Thus, full-fat soybean 111eal at 50 percent incorporation into the eliet can provicle the essential fatty acid needs of those fishes requiring 11-6 fatty acids and a signitlcant portion of the faHy acid requirements in those fishes requiring n-3s. The crude fat concentration of solvent-extracted soy productsis low. For example, SBM contains 0.52 percent 18:2n-6 and 0.08 percent 18:3n-3 (dry matter basis; NRC, 1994). Thus, the contribution of SBM, concentrates, mIel isolates to the esscntial fatty needs of most fishes is Ilot sigl1ificanL The carbohydrate fraction of soybeans, presentee! as the nitrogenfree extract in Table 8.2 and often referred to as the soluble carbohydrate traction, contains sucrase, raffinose, and stachyose as the primat)' oligosaccharides. Sucrose is gcnerally available to animais, but raffinose and stüchyose are not as animais lack the Œ-galactosidase nccessary to catabolize the complex sugar (Snyder and Kwon, 1987). Mineral concentrations of SBM, concentrates, and isolates are presented in Table 8.4 along with values for herring fishmeaL Concentrations of calcium, phosphorus, sodium, chlorine, sulfur, zinc,ancl selenium are lower in most say praducts compared to fish meal. The only exception is the concentration of sulfur in soy isolatcs, which îs similar to the concenq'ation found in fishmeaL As stated prevîously, minerais can be easily aclded to diets in a premix and they are relatively inexpensive. Common additions to minerai premixes in dîets fed to fîsh incIude zinc and selenium as weil as other minerais considered limiting. Furthennore, aquatic animais have multiple mechanisms for
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211
TABLE 8.4. Mineral concentrations (dry matter basis) of heated soybean seed, soybean meal (SBM), concentrates. and isolates compared to a standard fish meaLa.
Mineral Calcium (%) Phosphorus (%) Sodium (°;0) Chlorine (%) Potassium (%) Magnesium (%) Sulfur (%) Copper (mg/kg) Iron (mg/kg) Manganese (mg/kg) Zinc (mg/kg) Selenium (mg/kg)
Seeds, heated
0.28 0.65 0.03 0.03 1.89 0.31 0.33 17.8 88.9 33.3 43.3 0.12
Fish SBM 0.38 0.77 0.02 0.05 2.38 0.33 0.49 22.2 195.5 40.0 61.1 0.30
Concentrate
0.39 0.90 0.05 2,44 0.35 14.4 122.2 33.3
lsolates 0.16 0.71 0.08 0.02 0.29 0.09 0.77 14.1 148.9 5.4 36.9 0.15
meal
b
2.58 1.89 0.65 1.20 1.09 0.19 0.74 6.4 194.6 8.6 141.9 2.07
aValu8s from NRC (1998). bHerring fish meal.
obtaining minerais from the environment. There i5 significant ion exchange at the gill in fresh- and saltwater animais in an effort ta maintain osmotic balance. Calcium, sodium, chloride, and potassium are readily uptaken from the environment. Marine fish abo drink COpiOliS amoums of water, usually mcasured in Llhour/unit body weight, and obtain mineraIs directly t'rom their water intake. There is increasing data supporting minerai llptake through the skin as weil. Phosphorus (P) dcserves some attention as the form of P is different in oilseed crops from that in tish meal. The majority of P (60 to 80 percent of total) in plant tissues occurs in the form of myoinositol l, 2, 3, 4, 5, 6-hexa kis dihydrogen phosphate, also known as phytic acid (Erdman, 1979). This is a storage fonn of P in plants and a nutritionally unavailable fonD of Pin most animais. Bacteria possess phytase and can cleave the phosphate groups from the inositol ring, but vertebrates do not possess phytase in their gaslroÎntestina] tract. Ruminant animais are capable of using some of
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ALTERNATIVE PfWTEfN SOURCES IN A(WACULTUfΠDIETS
the P From phytate, but the passage of fooel through the gastrointestinal tract of fish is more rapid th,m in ruminants and the contribution of nutrients from bacterial action to fishes is not weIl understood. Phytate also interaels with cations, rcducing their availability. Thcre are six charged phosphate groups on the myoinositol ring that can a,nd will bind cations in the gastrointesünal tract. Once these cations are bound, availability is reduced. Cations that ean bind ta phytate include calcium, magncsium, iron, zinc, coppel', manganese, molybdenum, and cobalt (Erdman, 1979; Cheryan, 1980). That topic is considered in more c1etail in subsequent chaptcrs. Vilamin concentrations in hcated seeds, SBM, soy concentrate, and isolate are presentecl in Table 8.5 along with values for herring fish meaL Say products contain higher concentrations of biotin, Jolie acid, TABLE 8.5. Vitamin concentrations (mg/kg, dry matter basis, unless othe l'wise denoted) of heated soybean seeds, soybean meal (SBM), soy concentrate, and say isolate compared to herring fish meal.
Vitamin Biotin Choline Folic acid Niacin Pantothenic aeid Riboflavin
Seeds, heated
SBMa
0.27 2563 4.0 24.4 16.7
0.29 3034 1.54 24.4 16.7
Thiamin Pyridoxine
2.9 12.2 12.0
Vilamin B12
0
3.4 3.5 7.1 0
Vilamin E [)-Carotened
20.1 2.1
0.22
Concentrate
0.3 2.2 2.8
6.7 4.7 1.3 0.2 6.0
b
a Isolate
Fish meala,c
0.3 2.2 2,7 6.5 4.6
0.14 5705 0.4 100.0 18.3
1.8 0.3 5.9 0
10.6 0.4 5.2 433.3
(jJ~g/kg)
2.5
16.1
aValues from NRC (1998). bValues fram NRC (1994). cHerring fistl meal. dConversion of [3-carotene to vitamin A in swine· 1 mg of all-trans j)-carotene = 267 lU vitamin A, 80 fJ,g retinol, or 92 fL9 retinyl acetate (NRC, 1998).
l'roi cil! Fe('(18lldls Origillatillg/folll Soybealls
213
thiamin, and pyridoxine, but lower concentrations of choline, niacin, pantothenic acid, riboflavin, vitamin B 12' vitamin E, and vitamin A compared to fish lllcal. Therc are few vitamin availability data from feeclstuffs fcd to fish and most practical diets are formulated assuming 10w or negligible vitamin availability. As SBM is proccssed into conccntrates and isolates, most of the vitamin concentrations decrease. The concentrations of biotin, folie acid, and pyridoxine remain at similar or higher concentrations compared to SBM. A new soybean product was dcvcloped in the miel· 1990s that deserves mention. Expelled soybean meal is a product of extruding raw soybcans, pressing the cxtruded beans, and removing a smaller fraction of the lipid than in solvent extraction. Resulting nutritional concentrations are 45 percent crude protein, 6.5 percent fat, 5.5 percent fîber, 0.26 percent calcium, 0.63 percent phosphorus, 0.3 percent sulfur, 0.7 percent methionine, 135 percent total sulfur amino acids, 2.75 percent lysine, 0.7 percent tryptophan, 1.8 percent thrconine, and 2.0 percent isoleucinc. The expellecl meal apparently is beneficial for young swine and clairy caUle (Procluccrs' Natural Proccssing, 2004; http://www.pnpi.com/ExpMcal.htm).
ANTINUTRITIONAL FACTORS Soybeans contain a eliverse array of biologically active compounds, often refcrred to as antinutritional factors (ANF). These compounels tend to disrupt various aspects of nu trient absorption. There arc several mechanisms for climinishing the concentrations of ANF in soybeans, including traditional breeding programs, gcnetic modif1cation of seeds, heating ancl processing of harvestccl seecls. Extrusion of fish feeels also rceluees the concentrations of some ANF. Concentrations of ANF in soybean products are presentcd in Table 8.6. Processing of soybeans lo SBM and soy concentrates tends to clccrease concentrations of ANF.
Trypsinlnhibitors Trypsin inhibitors (TI) are commonly associated with soybeans. They are proteins found in soybeans that bind with trypsin and chymotrypsin in the gastrointeslinal tract of animais and effectively block
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ALTERNA71l'E PIWTErN SOURCES lN A(JUACULTUlΠDiETS
TABLE 8.6. Concentrations of the predominant ANFs in various soybean products. a Component
Raw soybeans
Tryps!n inhibitor, mg TI/g Lectin, fJ.,g/g ~aponin,
%
G1ycinin antigen, mg/kg [3-Conglycinin antigen, mg/kg
45-50 3,600 0.5
184,000 >69,000
Soybean meal Say concentrate
5-8 10-200b 0.6 66,000 16,000
