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Triticum aestivumWheatUseful reference: 236 A cereal widely cultivated in temperate countries and in cooler parts of tropical countries. Where wheat is not grown, it is usually imported for milling inside the country, as the importing of flour rather than wheat deprives the feed industry of the by- products on which it is based in many countries. The flowering head of wheat consists of a compact arrangement of spikelets around a central stalk. In threshing, the grain - unlike that of barley and oats comes away naked from the husk. The wheat endosperm is covered with two kinds of fibrous coating: a coarser outer layers called bran, and under it a less fibrous aleurone layer. The germ is at the base of the kernel. Milling separates the starchy endosperm from the rest of the grain. Whole wheat yields about 70% white flour and 30% offal, consisting of bran, aleurone and germ. In milling, wheat grain passes through about twenty-four processes before it becomes table flour. The more important of these are the breaker rolls, which rupture the bran so that bran and germ separate from the endosperm; the scalpers, which separate aleurone and pieces of the endosperm from the bran; and the flour bolters, which separate fibrous particles from the table flour. The terms used to designate the various by-products differ from country to country and are often poorly defined. The names also change with the type of wheat used in milling. The following diagram shows how the different by-products are produced. USES. WHEAT GRAIN. Wheat is not usually fed to animals because of its high price; however, unmarketable grain may be used for all classes of livestock. Whole wheat can only be fed to poultry over two months of age; for other animals it should be crushed, especially if it is from varieties with small hard kernels. If wheat is too finely ground, it will form pasty and very indigestible lumps in the mouth; large amounts (over 3 kg per day) can be fatal to horses. In concentrates, wheat can be included up to 25% for cattle, up to 30% for growing pigs, up to 50% for fattening pigs and up to 50% for poultry. Fresh wheat should not be fed to poultry. At these high rates there are definite advantages in including other cereals as well. SCREENINGS. This product obtained from the initial cleaning of the incoming wheat consists of weak seeds and undersized wheat grains. It is usually finely ground and mixed with other wheat offals rather than used separately. WHEAT-GERM MEAL. This valuable feed is rich in digestible protein and low in fibre, and contains about 10% oil that is rich in vitamin E. If kept for a few days it is likely to become rancid. 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. FEED FLOUR. This is the residue of the endosperm from the production of fine white table flour with low extraction (60-65%). It contains mainly the starchy portion of the endosperm and also some of the more nutritious aleurone layer. Seldom used alone, it is mixed with other offals to give wheat shorts and middlings (see below). BRAN. There is no sharp difference between fine bran and course bran. The bran fractions contain most of the vitamins and protein of the wheat grain. If screenings have been added to the bran, the product is called standard bran. Good bran should have a fair coating of flour and be in the form of large, dry and nonadherent flakes. Bran is a bulky feed that can be used to lighten dense, heavy feed mixtures. It has a slightly laxative effect, partly because the bran fibre is only modestly digested. Coarse bran is excellent for horses and cattle, which can be given up to 2 kg per day. Fine bran can be fed to horses and cattle in amounts up to 2 kg per days as well as to pigs and poultry. It can constitute up to 35% of the brood sow diet. Young pigs should not be fed bran. To lighten poultry mashes, up to 15% may be included. SHORTS. This is a mixture of fine bran and feed flour in proportions that vary according to the type (extraction rate) of table flour the mill produces. It is used in the same way as wheat middlings. WHEAT MIDDLINGS. This mixture of shorts and germ is the most common by-product of flour mills. If the proportion of ingredients is retained, middlings are often called mill-run or wheat pollard. Both shorts and middlings can be used for all classes of livestock. They are common - often up to 40% - in concentrates for cattle. Owing to their bulkiness it is difficult to formulate a satisfactory ration based on middlings for growing and fattening pigs. It has sometimes been found economical to include up to 45% middlings, but a more normal level of inclusion is 15-25%. Some middlings can be advantageously included in feed for layers, but practical considerations usually limit the content to less than 10%. Wheat middlings are reported to contain a factor that reduces the incidence and severity of gizzard erosion. Steam pelleting of wheat middlings increases their naturally low metabolizable energy and poor protein utilization in poultry diets as much as 30% and 17%, respectively, by rupturing the aleurone cells and exposing the content of the cells to attack by digestive enzymes.
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