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Corn gluten meal

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Description
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Common names 

Corn gluten meal, maize gluten meal, gluten 60, prairie meal [English]; farine de gluten, gluten de maïs [French]

Species 
Description 

Corn gluten meal is a by-product of the manufacture of maize starch (and sometimes ethanol) by the wet-milling process (RFA, 2008). Corn gluten meal is a protein-rich feed, containing about 65% crude protein (DM), used as a source of protein, energy and pigments for livestock species including fish. It is also valued in pet food for its high protein digestibility (RFA, 2008). In the USA and Canada, corn gluten meal is also used as a fertilizer and pre-emergent weed killer (Pasupuleti et al., 2010; Christians, 1994).

The wet-milling process of maize is described in the figure above. The process yields 5 main products: maize starch, maize germ oil meal, corn gluten meal, corn gluten feed and maize steep liquor. After cleaning and removal of foreign material, the maize grain is usually steeped in water with sulfur dioxide (SO2) for 24-40 hours at a temperature of 48-52°C. The role of sulfur dioxide is to weaken the glutelin matrix by breaking inter- and intramolecular disulfide bonds. Steeping at 45-55° C favours the development of lactic acid bacteria that produce lactic acid, lowering the pH of the medium and thereby restricting growth of most other organisms. At the end of the steeping phase, the maize kernels contain about 45% water, having released about 6.0-6.5% of their dry matter as solubles into the steepwater, and have become sufficiently soft to be pulled apart easily with the fingers (BeMiller et al., 2009). After steeping, the maize kernels are coarsely ground so that the germs are separated from the endosperm and used for oil extraction that bonds between molecules, and bonds within the molecule (between atoms) yields maize germ oil meal. The remaining steeping water is condensed into a steep liquor. The endosperm undergoes further screenings that separate the fibre from gluten (protein fraction) and starch slurry. Fibre (bran) is mixed with steep liquor and maize germ oil meal to create corn gluten feed (ISI, 2008; RFA, 2011). The fibre-free endosperm is centrifugated in order to separate the starch fraction and the gluten, which have different densities, resulting in almost pure starch (99% starch), and corn gluten meal (CRA, 2006).

Note: it is important to note that corn gluten meal should not be mistaken for corn gluten feed, which contains about 22% crude protein rather than 65% and is nutritionally completely different. The name similarity of these products is an occasional source of confusion, particularly in papers written by non-native English speakers.

Distribution 

Corn gluten meal is obtained wherever maize is used for starch extraction. It is distributed worldwide. Its production has become relatively constant since ethanol is now mainly produced by dry-milling, which yields corn distillers rather than corn gluten meal and corn gluten feed (RFA, 2008). In 2010-2011, feed consumption of both corn gluten meal and corn gluten feed (statistics do not differentiate between the two products) was about 14.9 million t. The biggest consumers were the USA (5.6 million t), the European Union (3 million t), South Korea (1 million t), Japan (0.94 million t) and other Asian countries (1.6 million t). The USA was the major supplier: they provided 2.1 million t of the 3.5 million t exported worldwide. Main importers were the EU, South Korea, Turkey, China, Japan, Israel, Egypt and Indonesia (Oil World, 2011).

In the European Union, the ban on genetically-modified (GM) maize and maize by-products resulted in a spectacular decrease in the importation of maize grain, corn gluten meal and corn gluten feed in the early 2000s (European Commission, 2007). The importation of GM maize and GM maize by-products is now strictly regulated in the EU, and the EFSA examines every new demand for GM maize products (European Union, 2003).

Processes 

Corn gluten meal can be fed wet or dried, but dried is more common.

Nutritional aspects
Nutritional attributes 

Corn gluten meal is a protein-rich feed containing from 60 to 75% crude protein (DM) (though lower values have been reported). It contains about 15-20% of residual starch in the DM and limited amounts of fibre (crude fibre 1% DM), fat (3% DM) and minerals (2%). Due to its high protein content, corn gluten meal is mostly used as a potential alternative to other plant or animal-based proteins (Leeson et al., 2005). However, like maize grain, its amino acid profile is low in lysine (1.7% of the protein vs. 6.3% for soybean meal and 7.5% for fish meal) and tryptophan (0.5% vs. 1.4% for soybean meal and 1.1% for fish meal). It also contains more methionine (2.4%) than lysine, resulting in an unbalanced profile for many livestock species, though the relatively good methionine content is valuable for laying hens. Corn gluten meal is also a source of energy, due to its high gross energy content (23.1 MJ/kg DM) and energy digestibility (more than 90% in ruminants and pigs). A constraint is its moderate palatability in land-based livestock (Leeson et al., 2005). Corn gluten meal is particularly rich in yellow xanthophylls (between 200 and 500 mg/kg DM) that are useful for pigmentation in poultry where high-colour chickens and eggs are prized by consumers (Blair, 2008; Coimbra, 2001).

Potential constraints 

Mycotoxin contamination

Like other maize products, corn gluten meal can be contaminated with mycotoxins. In 2009-2010, a worldwide survey found that corn gluten meal samples were frequently contaminated with mycotoxins, notably fumonisin and zearalenone (Rodrigues et al., 2012). Similar findings have been reported in China in 2006-2007 (Ao et al., 2008).

Ruminants 

Corn gluten meal is used as a source of protein in ruminants and particularly as a source of undegradable protein and metabolisable protein. However, the poor lysine content of corn gluten meal can be limiting and the replacement of traditional, lysine-rich protein sources such as soybean meal with corn gluten meal should be implemented with care.

Digestibility and energy content

The OM digestibility of corn gluten meal is generally higher than 90%, resulting in high ME values (16.4 and 16.8 MJ/kg DM) (Sauvant et al., 2004; Volden, 2011). Other sources have reported a True Digestible Nutrient value of 84% (NRC, 2001; Rocha Junior et al., 2003; Azevêdo et al., 2011b).

Protein value

The protein of corn gluten meal is potentially highly degradable in the rumen, with potential degradability values about 90% (Sauvant et al., 2004) or higher (NRC, 2001; Volden, 2011). However, the fractional degradation rate is very low (1.6, 2.5 and 5.2 %/hour) (Volden, 2011; Sauvant et al., 2004; NRC, 2001) resulting in low effective degradation rates (around 30%): corn gluten meal is the plant feed resource which provides the highest quantity of rumen undegradable protein, ranging from 45 to 50% DM.

The intestinal digestibility of the by-pass protein of corn gluten meal is high (90-91%), which is higher than in rapeseed meal (about 80%) and cottonseed meal (less than 90%), but lower than in soybean meal (more than 95%) (Sauvant et al., 2004; Yue Qun et al., 2007). For that reason, corn gluten meal is the best plant source of metabolisable protein. However, due to is low lysine content, the proportion of lysine in the metabolisable protein is also low (less than 3.5%; Sauvant et al., 2004). Consequently, it is important to evaluate carefully the lysine content of metabolisable protein in diets including large quantities of corn gluten meal as the lower dietary limit of the lysine/metabolisable protein ratio (as a percentage) is considered to be about 6.1%.

Dairy cattle

Corn gluten meal has been extensively studied in dairy cows. In most trials, corn gluten feed alone or in combination with other protein sources gave similar or better results than the control diets. Combinations of extruded soybeans and corn gluten meal, as the protein supplement, gave results similar to those obtained with soybean meal alone for lactating cows (Annexstad et al., 1987). A mixture of corn gluten meal and blood meal produced a lactation response similar to that obtained with soybean meal in mid-lactation Holstein cows (De Gracia et al., 1989). In high-yielding Holstein cows, corn gluten meal supplementation used to raise crude protein by 1.1 to 1.5 percentage point in the diets had a slightly negative effect in early lactation and a generally positive one in late lactation, which suggests that lysine may have been a limiting factor in early lactation (Holter et al., 1992). In Brazil, in cows with restricted grazing on Italian ryegrass, supplementation with a 60:40 blend (22% crude protein) of ground maize and corn gluten meal significantly increased milk production (Ribeiro Filho et al., 2009). In Iran, cows receiving a supplement of corn gluten meal, thereby increasing their by-pass protein intake, increased their DM intake, milk yield, milk protein content and body condition score, while reducing body weight losses (Aboozar et al., 2012). However, feeding a combination of distillers dried grains and corn gluten meal depressed milk protein production when compared with a soybean-based control diet, probably due to the lower lysine content of the maize-based products compared to soybean (Voss et al., 1988).

Growing cattle

In Brazil, corn gluten meal and cassava peels partly replaced energy concentrates, with no influence on DM intake, digestibility, microbial efficiency and nitrogen retention in heifers (Azevêdo et al., 2011a).

Sheep

In sheep fed according a programme of protein supplementation on alternate days, corn gluten meal was an effective substitute for soybean meal (Collins et al., 1992). The replacement of a blend of soybean meal and wheat bran with a blend of corn gluten meal and corn gluten feed had no negative effect on apparent digestibility of nutrients, or on N and energy balance in sheep (Milis et al., 2005).

Goats

Two trials with dairy goats have resulted in contradictory results. In Brazil, the replacement of up to 50% of soybean meal protein with corn gluten protein linearly decreased milk fat production and slightly depressed milk yield in dairy goats (Macedo et al., 2003). In Italy, a trial compared a highly degradable protein diet based on pelleted total mixed rations containing soybean meal, sunflower meal and urea, with a low-degradable protein diet including corn gluten meal in the pellets. The dairy goats fed the corn gluten meal diet had the highest milk fat, protein and casein concentrations, with no significant effects on other milk components and renneting properties. It was concluded that a decrease of rumen degradable protein did not negatively influence nutrient utilization, and milk production and composition in dairy goats (Laudadio et al., 2010).

Pigs 

Corn gluten meal is a valuable feed for pigs due to its high protein and energy content coupled with a low concentration of dietary fibre. The net energy content of corn gluten meal is slightly lower than that of maize grain but much higher (+ 40%) than that of soybean meal. In China, the metabolisable energy content of corn gluten meal was found to vary according to the origin of the product, but not significantly (Ji et al., 2012). The major drawback of corn gluten meal for pig feeding is its deficiency in lysine and tryptophan, though this is partly compensated by standardized ileal amino acid digestibilities that are higher for corn gluten meal than for maize and soybean meal (Knabe et al., 1989). It was possible to include up to 20 or 30% corn gluten meal in growing-finishing pig diets without adverse effects on growth performance, provided that diets were supplemented with synthetic amino acids (Almeida et al., 2011). Corn gluten meal could be included in weanling pigs diets at up to 13 to 15% without hindering performance (Richert et al., 1992; Mahan, 1993). Because phosphorus absorption from corn gluten meal is low, phytase addition is recommended in pig diets based on it (Rojas et al., 2013).

Poultry 

Corn gluten meal can be a valuable feed for poultry due to its high protein content, its high pigment (xanthophyll) content and its high ME content (typically more than 16 MJ/kg DM). However, its amino acid profile is deficient in lysine, which makes it unsuitable for meat-producing poultry (Crawshaw, 2004). It is also fairly unpalatable to poultry (Blair, 2008). However, the methionine content is relatively high, much higher than that of soybean meal and relatively close to that of fish meal, which is a desirable trait for layers diets (Crawshaw, 2004). The high xanthophyll concentration of corn gluten meal is valuable in markets where a bright yellow colour in egg yolks, skin, and fatty tissues is associated with good health and premium quality by the consumer, but less so in markets that prefer white chicken skins and light-coloured yolks. The inclusion rate of corn gluten meal in poultry diets is, therefore, driven in part by market demand in terms of colouring.

In intensive poultry diets, inclusion rates for corn gluten meal are generally no higher than 5-8% (Tangendjaja et al., 2011; Crawshaw, 2004). Higher rates have been tested successfully in non-industrial production systems. In Bangladesh, corn gluten meal included at 10% in pullet diets gave the desired intense egg coloration (Subarna et al., 2006). In Brazil, it was shown that in free-range chickens (slow-growing type) the optimal inclusion rate for corn gluten meal was 10%, starting in the growth phase (32-84 days) (Rabello et al., 2012). In India, including 9% corn gluten meal in broiler diets resulted in satisfactory results and was considered economic (Ismail et al., 2005). However, in Egypt, attempts to feed higher levels (20%) of corn gluten meal resulted in a lower feed intake and body weight gain in growing broilers. Only finishing broilers could be fed 20% corn gluten meal without deleterious effects (Abdel-Raheem et al., 2005).

Rabbits 

Corn gluten meal was safely used in growing rabbits up to 10-12% in a balanced diet (El-Husseiny et al., 1997; Siddaramanna et al., 2009). However, the use of corn gluten meal in rabbit feeding is severely limited, due both to its deficiency in lysine (which covers only one third of the lysine requirements) and to the quasi-absence of fibre. For these reasons, in Europe corn gluten meal is rarely used in commercial rabbit production, although other by-products of maize processing, such as corn gluten feed or distillers grains are used (de Blas et al., 2010). The presence of mycotoxins in corn gluten meal (Ao et al., 2008; Rodrigues et al., 2012) is particularly problematic in rabbit production, as the reported levels of fumonisin and zearalenone are deleterious for rabbit reproduction (Abdelhamid et al., 1992; Mezes, 2008).

Fish 

Corn gluten feed is considered as a good and palatable source of protein for fish and has been used in fish feeding in the USA since the 1970s (Raven et al., 1980). Because it is low in lysine, it is recommended to supplement diets rich in corn gluten meal with L-lysine or soybean meal. 

Rainbow trout (Oncorhynchus mykiss)

Corn gluten meal is a common component of rainbow trout diets. It has been used as a cheaper substitute for fish meal since the 1990s, when it was demonstrated that mixtures of plant proteins containing corn gluten meal could replace up to 66% of fish meal without compromising performance (Gomes et al., 1995). Corn gluten meal is now generally included at 15-50% in trout diets with other plant protein sources such as soybean products (soybean protein concentrate, soybean meal) (Prachom et al., 2013; Sarker et al., 2011; El-Haroun et al., 2007; Aksnes et al., 2006). However, it has been shown that maize products (including corn gluten meal) included at more than 18% reduced growth performance in rainbow trout (Stone et al., 2005). Diets with 50% corn gluten meal adequately supplemented with L-lysine resulted in satisfactory growth performance but depressed the feed conversion ratio (El-Haroun et al., 2007). In rainbow trout fry, the inclusion of corn gluten meal resulted in lower feed intake, and in a lower feed efficiency of supplementary L-lysine compared to other plant protein sources such as wheat gluten or a mixture of wheat gluten and sesame oil cake (Tran Thi Nang Thu et al., 2007). Processes such as extrusion had no effect on the nutritive value of corn gluten meal (Stone et al., 2005).

Corn gluten meal can be used to create environment-friendly feeds with a low phosphorus content, in order to reduce the amount of phosphorus discharged into water (Sarker et al., 2011; Stone et al., 2005). Xantophylls have been suspected of depressing pigmentation in rainbow trout, but no evidence was found of that effect, even at inclusion levels of 22 to 34% of the diet (Coimbra, 2001).

Atlantic salmon (Salmo salar)

Corn gluten meal has high protein and energy digestibilities, 96 and 79%, respectively, in Atlantic salmon, and is, therefore, considered a good alternative protein source for salmon (Burr et al., 2011). Average apparent and true amino acid availabilities were 78 and 92% for corn gluten meal, which is higher than for soybean meal (Anderson et al., 1992). Amino acids provided by corn gluten meal were shown to suit salmon requirements and it was suggested that it could replace up to 50% of the fish meal in salmon diets (Mente et al., 2003). However, increasing corn gluten meal in salmon diets resulted in lower digestibility, growth and feed intake. Feeding salmon on a mixture of soybean meal and corn gluten meal also had a negative effect on dressing percentage (Mundheim et al., 2004).

Nile tilapia (Oreochromis niloticus)

Corn gluten meal is very digestible to Nile tilapia: reported values for digestibilities of energy, protein and amino acids were all high, in the 89-91% range (Guimaraes et al., 2008; Koprucu et al., 2005). The benefits of replacing fish meal with corn gluten meal in tilapia diets are debated. Earlier studies have been quite positive. Nile tilapia fingerlings fed on corn gluten meal (16% inclusion) showed higher growth and feed intake, and a reduced feed conversion ratio (Wu et al., 1995). Another trial indicated that replacing fish meal with a mixture of alternative plant-based ingredients, including corn gluten meal, was possible and had no effect on fish growth or feed conversion ratio (Tudor et al., 1996). However, later trials have been less favourable. Replacing fish meal with corn gluten meal (30% inclusion) resulted in poorer growth, feed intake and a lower feed conversion ratio than when fish meal was replaced with soybean meal or full-fat soybeans, possibly because the diet, while supplemented with lysine, was still deficient in arginine, histidine and threonine (Goda et al., 2007). Feeding Nile tilapia with complex plant mixtures (soybean meal, corn gluten meal, dehulled linseeds, pea protein concentrate and canola protein concentrate) resulted in better performance (growth, feed conversion ratio) than in tilapia fed diets based on simple mixtures of fish meal alternatives, but even with complex diets performance was generally lower than with fish meal-based diets (Borgeson et al., 2006).

Crustaceans 

Pacific white shrimp (Litopenaeus vannamei)

Pacific white shrimps (Litopenaeus vannamei) were fed on plant protein-based diets containing corn gluten meal (5%) without any problems (Amaya et al., 2007).

Nutritional tables
Tables of chemical composition and nutritional value 

Avg: average or predicted value; SD: standard deviation; Min: minimum value; Max: maximum value; Nb: number of values (samples) used

Main analysis Unit Avg SD Min Max Nb  
Dry matter % as fed 90.0 1.7 87.3 96.2 1662  
Crude protein % DM 67.2 2.9 56.9 76.2 1659  
Crude fibre % DM 1.2 0.5 0.4 2.7 240  
NDF % DM 4.1 2.5 1.1 8.6 43  
ADF % DM 1.6 1.1 0.3 3.7 39  
Lignin % DM 0.3 0.1 0.2 0.6 15  
Ether extract % DM 2.9 1.2 1.0 6.5 625  
Ash % DM 2.1 0.8 1.1 4.6 406  
Starch (polarimetry) % DM 17.6 3.5 9.1 26.0 204  
Total sugars % DM 0.5 0.2 0.2 1.2 92  
Gross energy MJ/kg DM 23.1 0.8 21.2 24.1 36 *
               
Minerals Unit Avg SD Min Max Nb  
Calcium g/kg DM 0.3 0.3 0.1 1.2 132  
Phosphorus g/kg DM 4.0 1.7 0.8 7.8 153  
Potassium g/kg DM 1.0 0.6 0.2 2.4 14  
Sodium g/kg DM 0.8 0.8 0.1 3.1 92  
Magnesium g/kg DM 0.5 0.2 0.2 0.8 16  
Manganese mg/kg DM 9 5 1 14 6  
Zinc mg/kg DM 38 19 12 64 7  
Copper mg/kg DM 13 5 4 17 6  
Iron mg/kg DM 112 65 3 219 8  
               
Amino acids Unit Avg SD Min Max Nb  
Alanine % protein 8.5 0.6 7.5 9.6 57  
Arginine % protein 3.0 0.3 2.5 3.4 62  
Aspartic acid % protein 5.8 0.4 5.1 6.7 57  
Cystine % protein 1.8 0.2 1.5 2.1 53  
Glutamic acid % protein 20.1 1.3 18.0 22.2 57  
Glycine % protein 2.5 0.3 2.0 2.9 58  
Histidine % protein 2.0 0.2 1.7 2.4 52  
Isoleucine % protein 4.0 0.3 3.4 4.4 63  
Leucine % protein 15.9 0.7 14.7 17.9 64  
Lysine % protein 1.7 0.1 1.4 2.1 75  
Methionine % protein 2.4 0.2 2.1 2.7 57  
Phenylalanine % protein 6.1 0.3 5.5 6.6 64  
Proline % protein 8.7 0.4 7.9 9.8 33  
Serine % protein 4.9 0.3 4.4 5.4 58  
Threonine % protein 3.3 0.2 2.9 3.6 65  
Tryptophan % protein 0.5 0.1 0.4 0.6 32  
Tyrosine % protein 4.8 0.4 4.1 5.4 44  
Valine % protein 4.5 0.3 3.9 5.1 62  
               
Vitamins and pigments Unit Avg SD Min Max Nb  
Xanthophylls mg/kg DM 330 68 195 491 500  
               
Ruminant nutritive values Unit Avg SD Min Max Nb  
OM digestibility, ruminants % 96.1 2.1 94.2 99.9 5 *
Energy digestibility, ruminants % 99.1 1.6 94.6 99.1 5 *
DE ruminants MJ/kg DM 22.9 0.5 22.4 23.6 5 *
ME ruminants MJ/kg DM 16.6 0.5 16.6 18.2 5 *
Nitrogen digestibility, ruminants % 81.0 1.4 81.0 97.4 5 *
a (N) % 5.5 5.1 0.1 10.2 3  
b (N) % 47.6 39.3 8.7 87.2 3  
c (N) h-1 0.033 0.029 0.011 0.066 3  
Nitrogen degradability (effective, k=4%) % 27         *
Nitrogen degradability (effective, k=6%) % 22 9 8 34 7 *
               
Pig nutritive values Unit Avg SD Min Max Nb  
Energy digestibility, growing pig % 93.0 3.5 82.7 94.4 18 *
DE growing pig MJ/kg DM 21.4 1.0 18.6 21.9 19 *
MEn growing pig MJ/kg DM 19.8 0.5 18.0 20.0 18 *
NE growing pig MJ/kg DM 12.7         *
Nitrogen digestibility, growing pig % 86.2 4.0 85.3 95.0 5 *
               
Poultry nutritive values Unit Avg SD Min Max Nb  
AMEn cockerel MJ/kg DM 16.8 0.2 16.8 18.3 5 *
AMEn broiler MJ/kg DM 16.6         *
               
Rabbit nutritive values Unit Avg SD Min Max Nb  
Energy digestibility, rabbit % 89.2         *
DE rabbit MJ/kg DM 20.6       1  
               
Fish nutritive values Unit Avg SD Min Max Nb  
DE salmonids MJ/kg DM 19.1         *
Energy digestibility, salmonids % 83.0       1  
Nitrogen digestibility, salmonids % 96.0       1  

The asterisk * indicates that the average value was obtained by an equation.

References

Adamidou et al., 2009; ADAS, 1986; ADAS, 1988; Adeola, 1996; Adeola, 2003; AFZ, 2011; Agunbiade et al., 2004; Allan et al., 2000; Almeida et al., 2011; Aufrère et al., 1991; Bach Knudsen, 1997; Bourdon et al., 1974; Broderick et al., 1990; Burgoon et al., 1992; Burr et al., 2011; Campbell et al., 1983; Cave, 1988; Chiou et al., 1995; CIRAD, 2008; Cozzi et al., 1993; El-Haroun et al., 2007; Embrapa, 1991; Erasmus et al., 1994; Fialho et al., 1995; Guimaraes et al., 2008; Henderson et al., 1984; Ji et al., 2012; Knabe et al., 1989; Koprucu et al., 2005; Lekule et al., 1990; Lyman et al., 1956; Macgregor et al., 1978; Marcondes et al., 2009; Masoero et al., 1994; Maupetit et al., 1992; McNab et al., 1988; Mondal et al., 2008; Morrison, 1970; Moyano et al., 1992; Mustafa et al., 1997; Nadeem et al., 2005; Nengas et al., 1995; Rodrigues, 2001; St-Hilaire et al., 2007; Stutts et al., 1988; Susmel et al., 1989; Susmel et al., 1991; Trillaud-Geyl, 1992; Vérité et al., 1990; Vervaeke et al., 1989; Weisbjerg et al., 1996; Wiseman et al., 1992; Wohlt et al., 1991; Yamazaki et al., 1986

Last updated on 04/08/2014 22:16:40

References
References 
Datasheet citation 

Heuzé V., Tran G., Sauvant D., Renaudeau D., Lessire M., Lebas F., 2015. Corn gluten meal. Feedipedia, a programme by INRA, CIRAD, AFZ and FAO. http://www.feedipedia.org/node/715 Last updated on October 29, 2015, 14:09

English correction by Tim Smith (Animal Science consultant) and Hélène Thiollet (AFZ)
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