Wheat (Triticum spp.) is one of the most important staple food crops for humans: it provides about 20% of food energy and protein worldwide. It is the most widely grown crop in the world with 225 million ha harvested in 2009. Wheat grain production (682 million t in 2009) ranked third among cereals after maize and rice. Average biomass production of wheat is about 14 ton DM/ha.. Wheat grain is mainly processed into flour (whole grain or refined) for the production of a large variety of bakery products, pastries and confectionary. Durum wheat is a wheat species (Triticum durum) dedicated to semolina, couscous and pasta production. Wheat is also used in the distillery (including biofuel), brewery and starch industries.
The wheat plant is a strongly tufted (from 2-5 to 40 tillers/plant) annual grass, 0.4-1.2 m tall. It is highly variable in size, inflorescence and grain morphology, depending on species, variety and cultivar, each adapted to specific growth conditions or utilization. The root system includes seminal roots and adventitious roots. Culms are glabrous, erect, cylindrical, with solid nodes and hollow internodes. Leaves are flat, 1-3 cm broad x 20-38 cm long. Leaf size increases with leaf insertion on the culm. The inflorescence is a long, slender, somewhat flattened spike. The spikelets are borne at each node of the disarticulating (wild species) or tough (cultivars) spike rachis. Spikelets are awned or awnless, with between 2 and 9 flowers. The seed is an ellipsoid caryopsis, ventrally grooved that can be reddish-brown, yellow or white coloured.
Wheat provides several products used to feed animals:
Supply / Distribution
Wheat probably originated from the fertile crescent in the corridor extending from Armenia to the south-west coastal areas of the Caspian Sea in Iran. Current wheat species may have resulted from the hybridization in about 6000 BCE of the cold hardy diploid species Aegilops tauschii ssp. strangulata with the tetraploid Triticum turgidum (Emmer wheat).
Wheat is the most widely grown cereal grain, from the Arctic Circle to the higher elevations near the Equator (up to more than 3000 m above sea level). However, it grows best between 30° and 60°N and from 27° to 40°S. Wheat grows well when average temperatures are about 25°C and in areas where the annual rainfall ranges from 375 to 875 mm. It is, however, possible to grow wheat in places where rainfall ranges from 250 to 1750 mm, provided it is well-distributed. Wheat grows best with rather hot and dry summers (humidity below 10% is preferable) since humidity may promote fungal diseases. Wheat grows on all soil types with a broad range of soil pH (4.5-8.3), but prefers fertile dark soils rich in nitrogen. Soils should be well-drained. It can tolerate slightly saline soils (up to 4.5 dS/m electrical conductivity).
Wheat can be grown in tropical and subtropical regions provided the area is not too hot and humid. It is then generally grown in elevated areas during the cool and dry season. In these areas irrigation is often necessary: 45% of developing countries wheat production comes from irrigated fields. Irrigation should be done so that no waterlogging occurs.
Wheat grain is available worldwide. In 2007, the main wheat producing countries were China, India, the USA, the Russian Federation, France, Pakistan, Germany, Canada and Turkey. Most of these producers are also the main exporters, India being the only one that does not export its wheat production. The major importers in 2007 were Brazil, Italy, Egypt, the Netherlands, Japan, Indonesia, Algeria, Belgium, the United Arab Emirates and the USA.
In the European Union, almost half of the production goes to animal feeding. The major users of feed wheat are the Russian Federation, Germany, France, China, the United Kingdom, Spain, Canada, the USA, Ukraine and Denmark.
Wheat grain should be stored in a cool, dry and aerated place to prevent heating and/or gas accumulation (due to germination) and condensation that may lead to mold development. Wheat grain should be dried to below 14% moisture and kept in a clean place for storage.
Wheat grain can be fed whole or processed. Many processes can be used, including dry rolling, steam rolling, flaking or grinding followed by pelleting. The effects of processing (or absence thereof) are highly dependent on the animal species to be fed and on the production required: for instance, whole wheat grain is more suitable for lambs whereas pellets are more suitable for cows. Too fine grinding may cause flowing issues in feeding equipment, as well as digestive upsets in animals.
Low test weight wheats, which are often used to feed livestock, have variable kernel sizes that make them more difficult to process: some grains may end up unprocessed or ground too finely. In order to prevent too fine grinding, it is recommended to err on the side of under-processing when processing low test weight wheats.
High inputs crop
Wheat grown in intensive systems requires high levels of inputs, including herbicides, pesticides, mechanical power and fertilizers (N and K). These requirements may result in N leaching and water contamination with nitrates and residues.
In some areas, wheat cultivation may result in soil erosion and soil salinization (when wheat is irrigated). Introducing wheat can occasionally require deforestation, resulting in biodiversity losses.
Genetically modified wheat
As of February 2013, no genetically modified wheat has been made commercially available. Research on GM wheat is being carried out in Europe and in the USA in order to develop wheat resistant to glyphosate and fungal diseases, and that has enhanced baking properties.
Wheat is primarily a source of energy due to its high starch content (about 70% DM). It is richer in protein than maize and barley (11-13% DM for soft wheats vs. 8-10% for maize and 11-12% for barley) and can thus be used as a replacement for maize as a high-energy ingredient requiring less protein supplementation than maize. Hard wheats and durum wheats have a much higher protein content (more than 14-15% DM for durum wheats) than soft wheats. Due to the natural separation of husk from the grain during threshing, the fibre content of wheat is very low (crude fibre less than 3%), slightly higher than that of maize, but half that of barley and much lower than that of oats .
The chemical composition of wheat can be highly variable, particularly with regard to starch and crude protein content, depending on species, cultivars, growing location, climate, soil fertility, etc. For instance, wheat containing up to 23% DM as protein and 80% DM as starch has been reported in the literature, as well as wheat containing as little as 9% protein and 50% starch. Such variability means that periodic testing of batches of wheat is highly recommended. Wheat protein is relatively poor in lysine (2.9% of crude protein) but due to its higher protein content wheat contains much more lysine and more tryptophan than maize. Wheat grains with low test weights have a lower starch content but are slightly richer in protein and fibre.
A benefit of wheat as a feed ingredient is that the presence of viscous gluten improves pellet quality, reducing the need for a pellet binder. This effect becomes noticeable when wheat is included at 10% or more in the pellet.
WHEAT BRAN : BY - Product
#Wheat bran, a by-product of the dry milling of common wheat (Triticum aestivum L.) into flour, is one of the major agro-industrial by-products used in animal feeding. It consists of the outer layers (cuticle, pericarp and seedcoat) combined with small amounts of starchy endosperm of the wheat kernel. Other wheat processing industries that include a bran removal step may also produce wheat bran as a separate by-product: pasta and semolina production from durum wheat (Triticum durumDesf.), starch production and ethanol production.
It is important to note that wheat #bran is not a product with a universally accepted definition and clear boundaries. Though national regulations may contain mandatory requirements on bran composition, ingredients sold under that name encompass a wide range of wheat by-products. Milling yields variable proportions of flour, depending on the quality of the final product. The extraction rate (flour:grain ratio) goes from 100% for a wholemeal flour to less than 70% for pastry flour. Typical extraction rates range from 75% to 80%, resulting in 20 to 25% wheat offals.
Wheat bran represents roughly 50% of wheat offals and about 10 to 19% of the kernel, depending on the variety and milling process . In the industrial milling process, after a cleaning step that removes grain impurities, the grains are tempered (soaked to toughen the outer layers and mellow the starchy endosperm in order to facilitate their separation) and then subjected to a series of grinding operations that produce finer and finer flour particles. The first grinding steps yield coarse particles of broken wheat and bran, and the later steps produce other by-products. Milling by-products are traditionally named after their quality (fineness, colour, etc.) and/or the stage of the process at which they arose, with considerable variations between languages, countries, regions, milling processes and even mills. In industrial countries, these products used to be sold separately (coarse bran, fine bran, middlings, second clear, thirds, etc.) but are now mixed together in variable proportions.
Consequently, wheat milling offals form a continuum of products with a decreasing fibre:starch ratio, from the fibrous coarse brans produced by the first grinding steps to starchy feed-grade flours. Wheat brans sold for animal feeding are typically mixtures of true coarse brans and finer products from the later grinding stages. In rural and traditional milling, flour is directly separated from bran in a one-step milling and screening. This type of bran has a higher starch content and a higher nutritive value. In Ethiopia, farmers prefer high-density bran since weight indicates that the bran contains more flour and thus higher energy . The situation is made even more complex by the existence of wheat brans from other wheat species (durum) and wheat processing industries.
Wheat bran is suitable for livestock feeding and very palatable to most classes of animals. Wheat bran is a bulky feed that can be used to lighten dense, heavy feed mixtures. It can be readily incorporated into mashes. Good bran should have a fair coating of flour and be in the form of large, dry and non-adherent flakes. It is sold raw or pelleted.
Wheat bran is exported worldwide and is a major feed commodity. However, worldwide production figures are difficult to assess. Wheat production for human consumption (total supply minus wheat produced for animal feeding, seed or wasted) was estimated to be 456 million tons in 2007. When calculated using a bran production rate of 10-19% (see Description above), worldwide wheat bran production is comprised between 45 and 90 million tons. The main producers should be the main users of milled wheat: China, India, the USA, the Russian Federation, Pakistan, Turkey and France (about 75% of the production).
Protein, minerals, oil and fibre are mainly found in the outer layers of the grain, and wheat bran is richer in these nutrients than the whole grain. Wheat bran is relatively rich in protein (14-19% DM, sometimes higher) and minerals (4-7% DM), notably calcium (0.07-0.2% DM) and phosphorus (0.9-1.3% DM). Its oil content (3-5% DM) is higher than that of the whole grain. The fibre and starch contents are inversely correlated and extremely variable, as they depend on the relative amounts of envelopes, endosperm and other fractions mixed together. However, a product marketed as bran should contain relatively high amounts of fibre: crude fibre 7-14 DM, NDF 35-54% DM, ADF 9-16% DM and low amounts of ADL 2-4% DM. Wheat bran should also contain about 15-30% DM of starch (Feedipedia, 2011). Fibre is the main constraint for the utilization of wheat bran in animal nutrition, particularly in monogastrics. For that reason, the energy values of wheat bran (DE, ME, NE) are always lower than those of the whole grain, in all animal species.
Wheat germ, wheat germ meal, wheat germ oil meal, wheat germ oil cake
Wheat germ is a valuable feed rich in digestible protein and low in fibre, and contains about 10% oil that is rich in vitamin E. Sometimes the oil is extracted, yielding wheat-germ oil meal. Usually the wheat germ is mixed with the shorts to give a product called middlings
Wheat distillers grain
Wheat distillers grain, wheat distillers grains, wheat DDGS
· Spent grains, wet distillers grains, wet distillers grain, distillers wet grains, WDG
· Dried distillers grain, distillers dried grains, distillers dried grain, dried distillers grain, DDG
· Wet distillers grains with solubles, wet distillers grain with solubles, distillers wet grains with solubles, WDGS, DWGS
· Dried distillers grains with solubles, distillers dried grains with solubles, distillers dried grain with solubles, dried distillers grain with solubles, DDGS
· Condensed distillers solubles (CDS), Dried distillers solubles (DDS)
Wheat distillers grain is the main by-product from the distillation of alcohol from wheat grain. Distilleries produce alcoholic beverages, industrial ethanol and ethanol biofuel with the following by-products (definitions are given in Processes):
· Spent grains, wet grains, wet distillers grain (WDG), wet distillers grain with solubles (WDGS)
· Dried distillers grain (DDG), dried distillers grain with solubles (DDGS)
· Condensed distillers solubles (CDS), dried distillers solubles (DDS)
There are two main distillery processes, dry-milling and wet-milling. Dry-milling (or dry-grind) is the main process for producing ethanol. This process starts with grinding before steeping the grain in water, and results in ethanol and various by-products. In the wet-milling process, the grains are steeped and the kernels are separated into various fractions, which allows for the production of multiple food and industrial products, including starch, proteins, fructose, oil and ethanol. This process, which runs non-stop for months, yields higher amounts or ethanol than dry-milling and saves costs, labor and yeast. results in numerous by-products including wheat gluten meal (sometimes called vital gluten), wheat gluten feed and wheat germ meal. These by-products account for 25-30% of the ethanol value chain turnover. While official and trade definitions exist for the different wheat distillery by-products, the boundaries between these products may be somewhat fuzzy. In particular, the amount of solubles blended back to the distillers grain can be highly variable and the presence of solubles unspecified in nutritional studies. However, it can be assumed that the majority of sold wheat distillers grain are actually wheat distillers grain and solubles.
This datasheet deals primarily with the DDGS of wheat-based, dry-milling ethanol production.. The availability of DDGS has grown considerably since the 1990s, due to the increasing demand for biofuel caused by environmental concerns and subsequent regulations. In Europe, EU Directive 2009/28/EC set a target of a minimum 10% share of energy used for transport from renewable sources for each Member State in 2020. In the USA, E15, a transportation fuel containing 15% volume of ethanol and 85% gasoline has been authorized and available since 2001. While the USA mainly fulfil their needs with maize-based ethanol, wheat is the primary feedstock for biofuel in Europe, Canada and Australia. Wheat distillery by-products, such as wheat distillers, are thus mainly produced in those regions. While the dry milling process yields DDGS as the main by-product, the wet milling process provides high value products such as gluten (used in the baking industry and as an emulsifier or thickener), bran (used in cereal foods), germs (used in bakery products and for some high value cosmetic uses) and flour
Distillery by-products have a long and rich history in animal feeding. They used to be considered offals and were dumped in sewers and rivers. Spent grains were sold at a low price to local farmers as animal feed. The first study on feeding distillers grain to cattle was published in 1907. Wheat distillers grain is a valuable feed ingredient, usually richer in protein than maize distillers grain, lower in fat and higher in fibre, and can be fed to most classes of livestock. Like maize DDGS, wheat DDGS was first used in ruminant feeding, but, due to its higher availability and a better knowledge of its nutritional value, it is increasingly used for non-ruminants, especially pigs. Wheat distillers grain may be used as fertilizer as it is an effective and slow-release source of N, P and other nutrients.
Supply / Distribution
Wheat ethanol production used 6.3 million t of wheat worldwide in 2010, an amount that is expected to reach 15 million t in 2020 (OECD-FAO, 2013). Assuming that 1 t of wheat processed into ethanol yields about 372 L of ethanol and between 295 and 400 kg DDGS (10% moisture), worldwide wheat DDGS production was about 1.9-2.5 million t in 2010 and will reach 4.4-6 million tons by 2020. 2010, France and Canada were the main producers of wheat DDGS with 0.56 and 0.5 million t respectively.
Ethanol manufacturing process
In the first step of the dry-milling process, the grain is either ground or milled to produce bran-free flour. The ground grains or the flour are then mixed with water and enzymes (amylases) to produce a mash where starch hydrolysis occurs (liquefaction step). This mash is cooked to kill the bacteria that produce undesirable lactic acid. Enzymes are added to the mash to transform starch into dextrose .. After saccharification, yeast is added to start the fermentation process, which produces a "beer" and CO2. The beer passes through a continuous distillation column to yield alcohol at the top of the column. The product that remains at the bottom (whole stillage) is centrifuged and yields wet grains (also called spent grains) and thin stillage. If the bran has been removed from the grain prior to fermentation, it may be added to the wet grains. With some processes, fats and fibre are removed in the early steps of the process and protein is concentrated in the final distillers dried grain, which is then called high protein distillers grain (HPDG).
Wet grains may be fed to livestock directly or they can be dried to produce dried distillers grain (DDG). Thin stillage can be sold as high-moisture feed, or it can be dehydrated to produce condensed distillers solubles (CDS, also called syrup). Condensed distillers solubles and distillers grain are often blended together to prepare wet or dried distillers grain and solubles (WDGS or DDGS). When the bran is added back at the end of the process, the distillers grains contain more starch. In addition to ethanol, the fermentation process produces 3% of yeast and 4% of glycerol at may be recovered in the DDGS residue and affect its composition.
While dry-milling ethanol manufacturing follows the process described above, the nature of the end products (beverages, industrial alcohol, biofuel), local know-how and innovation require specific adaptations, resulting in by-products of variable composition. It should be noted that, as of 2013, wheat ethanol by-products are still evolving due to changing technologies and biofuel demand.
Whisky wheat distillers
Wheat is the main feed material in certain whisky distilleries. The mash is filtered after the liquefaction step, producing wort and a solid by-product called draff or distillers spent grain. The wort undergoes further fermentation while the draff is dried or pressed before being fed to animals. The alcohol-free effluent that remains at the bottom of the distillation column is called spent wash or spent lees. This product, which contains enzymes and yeast, can be dried to yield dried distillers solubles.
Wheat distillers solubles contain xylans and arabinoxylans that are not broken down during the process and result in a high viscosity level in the solubles. Wheat solubles are, therefore, more difficult to dry than maize solubles. Wheat solubles can be centrifuged so that the solids can be further dried into distillers concentrate. As in ethanol production, the spent grains are often mixed with the solubles, resulting in wheat distillers dark grains. It is important to note that whiskies are often the result of the distillation of blended grains that may include maize, wheat, barley and rye. The by-products are, therefore, not wheat distillers in the strict sense. Single malt whisky is usually made from barley (and sometimes rye). In some distilleries of Scotland, where wheat is the sole feed material for whisky, the nutritive value of wheat distillers dark grains is significantly higher than that of malt distillers dark grains.
Wheat DDGS is rich in protein, which ranges between 30 to 40% DM, similar to rapeseed and sunflower meals and slightly higher than for traditional (not high protein) maize DDGS. Wheat DDGS has low concentrations of starch and soluble sugars. When the whole grain is used in fermentation, the final starch content of the DDG is about 4.5% DM. When the bran is removed before fermentation and added back at the end of the process, the starch content tends to be much higher (10-25% DM) with a large variation. The NDF content of wheat DDGS is also variable: wheat DDGS from whole grains have a slightly higher NDF content than wheat DDGS from milled grains (32 vs. 27% DM). The fat content of wheat DDGS is low (5% DM) and less than half that of maize DDGS. Because wheat solubles are high in fat (up to 34%) and low in NDF, the more solubles that are added to wheat DDGS, the higher the fat and the lower the NDF content of the distillers grain.
The composition of wheat DDGS is much more variable than in the original grain. In addition to the variability inherited from the grain itself (cultivar, growing conditions), there are large differences between ethanol plants due to: the method of grain preparation (grinding or milling); the fermentation process (type of enzymes and yeast strains); the amount of soluble fractions (richer in protein) blended with distillers grains; the duration and temperature of drying; and to possible further fractionations (separation of proteins, etc.) of the non-starch fractions As noted above, the reintroduction of bran at the drying stage results in a product containing more starch and less fibre. Adding more solubles increases the fat content and lowers NDF. The blend of different raw materials also contributes to the final DDGS. In some ethanol plants, wheat is blended with maize before distillation, which modifies the protein, phytate and energy contents of the final product.
Another source of variability is the heat damage occurring during the drying process. Wheat DDGS that have undergone high processing temperatures will have a reduced protein degradability in ruminants and amino acid availability in monogastrics. Depending on the composition, and more importantly on the drying process, the colour of wheat DDGS can vary from light yellow to dark brown. For instance, the luminance (L) values of 10 European wheat DDGS ranged from 43 (black products) to 63 (yellow products) in the study of . These authors suggest that wheat DDGS with L values lower than 50 have been overheated with a high occurrence of Maillard reactions. As DDGS become darker under high temperatures, light-coloured wheat DDGS should be preferred for monogastrics as their amino acid content and availability might be higher.
The amino acid profile of wheat DDGS is partly similar to that of the initial grain. However, yeasts used for starch fermentation represent an additional protein source equivalent to about 5% of the total DDGS protein content. In addition, the level of soluble fractions added into distillers grains may be variable and influence the protein content and the amino acid profile. Despite these potential sources of variability, the amino acid profile is quite comparable in wheat and wheat DDGS, except for lysine and arginine contents, which are lower for wheat DDGS. The lysine and arginine levels in the crude protein are highly variable, even in light-coloured products: 1.7 to 3.0% and 3.7 to 4.6%, respectively, in the study of . Unlike wheat or its milling by-products, poor correlations exist between lysine/arginine contents (when expressed in % DM) and the crude protein content, such that the latter cannot be used as a single indicator of lysine or arginine levels in wheat DDGS.
Minerals are three times more concentrated in wheat DDGS than in wheat grain. Phosphorus is less bound in phytic acid than in the wheat grain, and is more available to pigs and poultry.