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According to the notation in the outline classification, energy feeds are low-protein concentrates. The upper limit for protein is conveniently set at 20 percent, because this figure then includes wheat bran which is otherwise difficult to classify. However, it is the entire seed of the cereals that is the typical energy feed./ If an average is taken of the protein, fat, fibre, TDN, Ca and P figures for the six common grains (barley, corn, milo, oats, rye and wheat), a workable chemical description of an energy feed in terms of those nutrients and proximate principles most useful in determining its proper place in a livestock ration will result. Such data are shown in Table 12.Table 12 Typical Composition of Cereal Grains Feed Name Crude Protein Ether extract Carbohydrate Total (%) Dig for swine (%) Chemical score (%) Crude fibre (%) N-free extract (%) Barley, grain 11.6 8.2 20 1.9 5.0 68.2 Corn, grain 9.3 7.5 28 4.3 2.0 71.2 Oats, grain 11.8 9.9 464 4.5 11.0 58.5 Rye, grain 11.9 9.6 50 1.6 2.0 71.8 Sorghum, milo, grain 11.0 7.8 - 2.8 2.0 71.6 Wheat grain 12.7 11.7 37 1.7 3.0 70.0 Average 11.4 9.1 - 2.8 4.2 6.8 Feed name Energy Minerals Cattle Swine Calcium (%) Phosphorus (%) DE (kcal/kg) ME (kcal/kg) TDN (%) DE (kcal/kg) ME (kcal/kg) TDN (%) Barley, grain 3257 2671 74 3080 2876 70 00.08 0.42 Corn, grain 3659 2927 81 3569 3351 81 0.02 0.29 Oats, grain 2982 2446 68 2860 2668 65 0.10 0.35 Rye, grain 3336 2735 76 3300 3079 75 0.06 0.34 Sorghum, milo, grain 3139 2475 71 3453 3229 78 0.04 0.29 Wheat, grain 3453 2832 78 3520 3277 80 0.05 0.36 Average 3289 2698 75 3297 3080 75 0.06 0.34 5.1 Chemical Characteristics5.1.1 ProteinFrom the above table it will be seen that an energy feed is likely to contain about 12 percent crude protein of which between 75 and 80 percent is digestible. (Throughout this section digestible refers to apparent digestibility unless otherwise stated.)In practice , one will not go far astray by assuming energy feed protein to be 75 percent digestible. The quality of the protein of energy feeds is uniformly low as measured by any scheme that rates biological value numerically. All feeds of this group show lysine as their first limiting amino acid, which is of importance in the choice of a protein supplement to be used in a balanced ration. It also explains why substitution between energy feeds is not likely to alter appreciably the protein quality of the mixture.5.1.2 AshEnergy feeds are low in calcium. In practice, they are often neglected in making calculations for calcium supplementation. The content of phosphorus, on the other hand, is enough that some classes of pigs, and sometimes cattle and sheep also, need no special supplements, but this will depend on the kind and amount of roughage also fed to the herbivorous species.5.1.3 CarbohydratesAbout two thirds of the weight of the seed is likely to be starch, which will usually be about 95 percent digested. Not only is this high concentration of easily digested carbohydrate the distinguishing feature of energy feeds, but variation in this characteristic determines the consequences of substituting among feeds of this category.5.1.4 FatThe cereal grains belonging to the energy feeds normally contain from 2 to 5 percent ether extract, but a few by-product feedstuffs contain up to 13 percent fat, as does rice feed, the mill-run by-products of the manufacture of polished rice. Oat groats contain 7 or 8 percent fat, as does corn, hominy feed. The-fat of non-oily seeds is concentrated in the germ, and any processing that removed an appreciable proportion of the protein or carbohydrate, but not of the germ will leave a by-product with higher fat content than the parent seed. A knowledge of the processing involved in the production of a by-product feed is often helpful in understanding the composition of the product. The official definition of feeds may partially define the processing of by-products, as will the international feed names.The production of starch, on the other hand, involves a wet-milling process. The corn grain, after being softened with warm water and slightly acidified, is partly macerated and then allowed to soak in water in large tanks. The germ, because of its oil content, floats to the top, where it is removed, defatted, and dried into corn germ meal. The residue from the germ separation is reground and sifted to remove the hulls, bran tip cap, and other fibrous material. The gluten and starch are removed from the remaining mass in suspension and later separated centrifugally. The coarse residue made up of hulls, bran, etc.5.1.5 Crude fibreThe average crude fibre of the energy feeds is about 6 percent but individual feeds vary considerably. The upper limit for concentrates is taken as 18 percent, partly because in Canada - by legal definition - feeds with over 18 percent fibre must be registered as roughages. In particular, the coarse grain (barley and oats) may show wide deviations in fibre from sample to sample, ordinarily because of either an increase in hull or a decrease in the starch filling of the groat. Differences in fibre affect markedly their available energy value and hence their relative feeding value. The most important consequence of substitution between energy feeds is usually traceable to differences in the crude fibre of the products. Fibres of different origin are often quite different nutritionally (see Table 13).Table 13 Digestibility of Crude Fibre Crude fibre from; Class Coefficient of digestibility (%) Common name International feed name 1/ Wheat Wheat, grain 4 33 Wheat bran Wheat, bran, dry milled 4 36 Wheat shorts Wheat, flour by-product, 7 fibre 4 60 Oats Oats, grain 4 32 Rolled oats Oats, cereal by-product, ground more than 2 fibre 4 80 Oat clippings Oats, grain, clippings 1 58 Oat hulls Oats, hulls 1 40 Barley Barley, grain 4 45 Barley feed Barley, pearl by-product, ground 4 18 Brewer's grain Grains, brewer's grain, dehy 5 49 Malt sprouts Barley, malt sprouts, with hulls, dehy, more than 24 protein 5 83 Flaxseed Flax, seeds 5 84 Linseed oilmeal o.p. Flax, seed, mech extd ground 5 50 Linseed oilmeal solvent Flax, seed, solv extd ground 5 43 Soybeans Soybean, seeds 5 37 Soybean oilmeal Soybean, seeds, solv extd toasted ground 5 68 Corn Corn, grain 4 30 Corn bran Corn, bran 4 63 Corn gluten feed Corn, gluten with bran, wet milled dehy 5 78 Corn oilmeal Corn, germ, dry milled, solv extd dehy 5 82 Corn distillers' grains Corn, distillers grains, dehy 5 64 1/ International feed names have been included to illustrate how much more information about a feed they giveIt seems probable that processing which! involves soaking improves the digestibility of the fibre. The digestibility of the fibre of corn grain is 57 percent, but that of corn bran, corn gluten feed, corn oil meal, and corn distillers' grains ranges from 72 to 92 percent, with an average of 80 percent. Solvent extraction also appears to have improved the digestibility of the fibre of flaxseed and of soybeans.These data are from ruminant digestion trials and may be too high for omnivora. Regardless of species of animal, any part of the apparent utilization of the fibre of these feeds, not due to chemical error, must be due to attack by digestive system microflora. One might argue that the unprocessed fibre of seeds, which in its natural state is an outer protective coating of the seed, is relatively resistant to bacterial attack. This resistance may be due to lignification, or to waxy, horny, or other weather-resistant coatings. In the milling or wet processing of such seeds, some of these coatings may be partially disintegrated or dissolved, thus exposing the cellulose to easy attack by microorganisms of the digestive system. 'Digested' crude fibre, of course, yields as much energy to the animal as digested starch.Thus, although we may not be able to predict the reaction of the animals to a change in the source of crude fibre in a ration, we can usually trace the important changes in the feeding value of a ration that are caused by energy feed substitution, directly or indirectly, to the crude fibre. It is also generally true that amount of fibre and of available energy of energy feeds of feed mixtures are negatively correlated. Thus, raising the percentage of fibre means greater bulkiness and lower available energy, which in turn demand larger amounts of feed. In other words, high-fibre feeds are relatively less efficient sources of productive energy.5.2 Non-chemical Characteristics of Energy Feeds5.2.1 BulkIn a general consideration of characteristics of energy feeds as a group, there are some non-chemical characteristics we should mention. The first one in order of importance is probably bulkiness. A bulky feed is relatively low in its yield of biologically available energy. We can usually assume safely that among energy feeds DE or TDN is positively correlated with bulk density. The reason for this relationship is ordinarily traceable to the percentage of fibre in the feed, because of the four potential energy-yielding fractions, crude fibre is likely to be the least digestible. We get an idea of the situation from examining a few typical energy feeds, though we can interpret the figures only in general terms, for two reasons. First, figures for weight per unit volume of ground energy feeds are subject to considerable error, because of the difficulty in controlling the degree of packing of the feed when filling the measure; and second, values for the TDN of specific feeds are determined directly or indirectly. In Table 14 we present typical data for TDN, bulk density and percent of crude fibre of a few of the more common energy feeds. Figure 3 shows the trends of these relationships graphically.Table 14 Relationship of TDN, Bulk Density, and Percent of Fibre in Some Ground Energy FeedsFeedTDN (swine)Bulk density (g/litre)Percent of fibreWheat, grain808104Corn, grain807502Rye, grain757502Barley, grain705606Oats, grain6535510Wheat, standard middlings643857Wheat, bran572559Oat, mill feed2315027The significance of these relationships lies in the consequences of substitutions between energy feeds in a meal mixture formulation. Obviously the use in a meal mixture of a bulky feed in exchange for a heavier one will mean a lowering of the TDN of the mixture; consequently, more of the new mixture will be needed to meet the total energy needs of an animal. Put into other terms, bulky feeds are less efficient when we measure efficiency as feed required per unit of gain for an animal or for its production.Fig. 3 Relationship of TDN of swine feeds to weight per unit volume and to percent of crude fibre, = intercept of TDN and percent of crude fibre of a feed; o = intercept of TDN and pounds per quart of the same feed. Regression fitted by inspection.Simple restriction of total feed allowance has undesirable effects on animals' behaviour. They are continuously hungry and hence restless and perhaps irritable. If they are in groups, feed restriction leads to fighting for food and to the uneven distribution of the limited supply between the more and less aggressive individuals. The stockman's way of solving this management problem is often to feed a light, bulky feed in quantities sufficient to satisfy appetite, but at the same time to restrict the intake of TDN as desired. Thus, wheat bran, alfalfa meal, oat feed, etc., are sometimes deliberately incorporated in a mixture because of their low available energy. Such rations can be self-fed without the undesirable consequences of heavy intakes of more concentrated rations.The more serious situation is where cost of feed versus cost of TDN is involved. Ordinarily, bulky feeds cost less per ton than dense feeds. If the price is in proper relation to the TDN it may matter little which feed is used. The increased quantity of feed needed to supply the available energy will be balanced by its lower cost per pound. Unfortunately, feeders may not have the data necessary to determine the equivalent values. For many samples of feed no data may be available.The problem of bulkiness of feeds arises again in the feeding of very young animals, which, because of limited gastric capacity, cannot consume enough of a bulky feed to meet their energy needs for the rate of growth desired. High fat in a man-made ration, however, is often a liability because of its unstable nature. Experiments with puppies weaned at two weeks, guinea pigs at two days, pigs at ten days, and calves at two weeks, all show that self-fed, dry, low-fat rations can permit as rapid gains in body weight and be nutritionally as satisfactory as liquid milk in all other ways. When such rations are fed as a water gruel, the progress of the young is less satisfactory, unless enough fat is incorporated to maintain, in spite of the water dilution, the energy level at that of the dry meal.5.3 Quality in Energy FeedsSample-to-sample variation in quality is a special problem with energy feeds. The important feeds of this group fall into two subgroups of crude fibre. Corn, wheat, and rye or a type of plant seed that is without an enveloping hull make up one group. Barley and oat kernels, on the other hand, after threshing, remain encased in their flowering glumes, and because of this attribute, they are referred to as coarse grains. Because of this division of energy feeds, it may be helpful in considering quality to discuss in some detail the characteristics that give various energy feeds their special nutritional properties or that require consideration in making substitutions in ration formulation.5.3.1 Corn (maize)Of the energy feeds of the low-fibre group, corn is the key feed in livestock rations. As seen in Table 15, it is the lowest in crude protein and highest in available energy. Under favourable conditions of growth, a hectare in corn will produce about twice as much TDN, or useful energy, as in any other cereal grain. This high production is an economic consideration and makes it clear why corn is so important a crop in areas having climatic conditions favourable for its growth.Table 15 Relative Values of Energy Feeds as Carbohydrate ConcentratesGrainPercent of protein (Morrison)Percent of net energy (Morrison)Total feed value (Kellner)Corn (maize), grain74100100Barley, grain918698Kafir, grain9293-Milo, grain8793-Oats, grain928895Rye, grain748697Wheat, grain1009795The nutritional properties of corn cannot be dealt with so simply. Corn, like all other grains, is subject to variation in make-up because of varietal differences and the specific conditions under which it is grown and harvested. Locally produced samples may differ from published average figures for chemical composition.The figures for the make-up of corn may be more meaningful if we look at them in relation to the recommended proportions of nutrients in a meal mixture for market pigs. Of course, the comparisons must be general, because rations for other classes of stock will differ from those for a market pig.We can see at once from Table 16 that if corn is introduced into a balanced ration, it will lower the protein, calcium, phosphorus, manganese, and niacin. It is generally recognized that the quality of protein in corn will not meet non-herbivore needs. When corn is used for cattle or sheep feeding the calcium and sometimes the phosphorus may be adequately provided by the roughage, and the quality of protein is, of course, not an important factor. But as a source of energy, regardless of how one chooses to measure it, corn stands at the top among the energy feeds. For cattle feeding, perhaps other than for adult breeding stock, the feeding problem we meet most commonly is how to provide enough energy to permit growth, production or fattening.High energy may be a liability, for there are situations where the animal or the product may be subject to damage by rations of high energy. For market-hog feeding the high energy of corn will, under full or self-feeding, produce a carcass with more fat than is desired for so-called "lean" bacon. The rashers from corn-fed carcasses are also likely to have a smaller "eye of lean" as has been shown in experiments at Macdonald College (see Figure 4). This overfinish occurs merely because the more rapid gains in weight have brought the pigs to market weight at younger ages and hence with less muscle development that would be found on older pigs.As we might expect from their nutrient make-up, wheat shows the same tendency as corn to fatten, while oats, which have five or six times as much crude fibre and about 20 percent less TDN (for swine) produces a bacon rasher with 40 percent more lean and 50 percent larger "pork chop" eye of lean.Fig. 4 Typical bacon rasher from between third and fourth lumbar vertebrae for differing diets. (Oat fed)Fig. 4 Typical bacon rasher from between third and fourth lumbar vertebrae for differing diets. (Wheat fed)Fig. 4 Typical bacon rasher from between third and fourth lumbar vertebrae for differing diets. (Barley fed)Fig. 4 Typical bacon rasher from between third and fourth lumbar vertebrae for differing diets. (Corn fed)Table 16 Proximate Composition of Hull and Groat of Oats and BarleyFeedPercent of crude proteinPercent of fatPercent of fibrePercent of TDN (ruminant)Oatsgrain12.65.28.967.0hull2.71.130.333.0groat15.95.91.992.0Barleygrain11.92.44.576.0hull5.91.326.441.0groat11.62.02.478.0Economically the variation in the protein percentage of corn may be highly important. In compounding batches of balanced rations, much more protein supplement may be needed with low-protein corn than with high-protein corn to prepare a mixture of some desired percentage of protein. Assume a ration is to be compounded with corn as the energy feed plus a mixed protein, and that a final mix of 15 percent protein is wanted. We calculate as follows:Case ICase IITwo other characteristics of corn should be mentioned. The one concerns its fat (or ether extract) content, which is higher than the average of energy feeds. This is both an asset and a liability. There is little doubt that a part of the acceptability of corn to animals is traceable to its fat component, not on the physical nature of the ground grain. Ground corn is not dusty and, unless ground to an abnormally fine module, does not become pasty with mastication. Although there is no direct proof that the high palatability of corn to all classes of stock is traceable to the fat, it is probably significant that in feeding studies at Macdonald College the addition of about 5 percent vegetable oil improved the acceptability of dry, low-fat diets for young pigs, puppies and guinea pigs. Without the oil the rations contained about 2 percent ether extract. That the oil did not improve the diets otherwise is evidenced by the fact that they were no more efficient per calorie in producing weight gains than the low-fat mixtures.The high fat level, however, can be a distinct liability, since ground corn goes rancid easily. The effect may be slight, and may represent merely a superficial loss of palatability, or it may be extensive enough to result in heating or molding with the attendant loss in nutritive value. In general, ground corn cannot be stored without risk of such damage.The other characteristic of corn is its moisture content. Samples of corn as harvested are likely to vary more in water content than those of any other grain. They may range from 8 percent water for fully mature corn to 35 percent for frosted immature grain. Ear corn containing over 25 percent water, and shelled corn containing more than about 15 percent, will not store without damage in the usual types of cribs or bins. Aside from the effect of moisture content on storage, the nutritive value of the grain will decline as it is "diluted" with more and more water.5.3.2 The coarse grainsAs we have already implied, it is the glume on the hull that accounts for the higher fibre of the so-called coarse grains, as is clearly shown in Table 16, giving the pertinent data for barley and for oats.The difficulty with these grains is that the proportions of groat to hulls are widely variable within the species, and are further modified by seasonal growing conditions. Not only do the seeds themselves vary but the crops as harvested may include, in addition to the grain intentionally planted, the seeds from an assortment of other plants of volunteer origin from a previous crop or from weed impurities in the planting grain. Corn (maize) and wheat are relatively free (or are easily freed) from such contaiminants, but with barley and oats purity of sample is often a factor influencing feeding value.5.3.3 BarleyMany of "the problems of nutritional quality in energy feeds are particularly well-illustrated by barley as it is grown, sold, and used in Canada. This grain may be grown for malting purposes or for feeding livestock. The Canadian scheme by which the producer is paid for barley delivered to elevators involves a grading according to the purity of the crop, its variety, and its soundness. Samples, which because of admixtures of seeds from grains other than barley, or because of frost or heating damage or poor filling of kernels, are not suitable for malting, are classed as feed barley.There are three U.S. grades for feed barley. They are partially defined in Table 17. As we can see from this table, no. 1 feed barley is essentially pure barley, but because of frosting or for some other reason it is below the standard weight of 48 lb per measured bushel for malting barley. Barley is also found in this category because of variety and is not suitable for malting. (Some varieties of barley peel too easily and, consequently, are not wanted in malting grades.) Barley that is still lighter in weight per bushel and that may also contain up to 10 percent other material is classed as no. 2 feed. The no. 3 feed grade has no minimum weight per bushel and, furthermore, need only be 80 percent in purity.Table 17 Partial Description of Feed Grades of Western Canadian Barley Grade name Minimum lb per bushel Maximum tolerance of foreign material Percent of weed seeds (to large to pass 4/64 screen) Percent of wild oats Percent of other grains Percent of total foreign material not to exceed No. 1 feed 46 1 4 4 4 No. 2 feed 43 2 10 10 10 No. 3 feed - 3 20 20 20 The botanical make-up of the foreign material in barley as harvested (presuming pure barley was seeded) will depend largely on what crop was grown on the area the year immediately preceding and on the extent of the weed pollution. An extensive survey of the 1949 Western Canada barley crop deliveries to county elevators yielded the figures in Table 18 on purity and chief grain diluents.Table 18 Botanical Make-up of Barley as Harvested Percent of oats Percent of wheat 0 5 11 15 20 25 0 52 11 2 0.5 0.5 0.5 5 12 4 2 0.5 10 8 2 1 15 1 1 0.5 20 0.5 25 0.5 Table 18 indicates that a little more than half the individual crops as harvested were essentially pure barley, and balance of the crops on the whole would be similar in feeding characteristics to mictures containing 80 percent barley. Similar surveys in subsequent years revealed the same distribution of the "barleys as harvested". All commercial Canadian feed barley contains approximately the maximum tolerance of nonbarley. This is accomplished by blending at terminal elevators, sometimes with wild oats and coarse grains removed from wheat.To describe the feeding value of barley as this crop actually appears in commercial channels in Canada is, consequently, not a simple matter. To be realistic we must consider under the name barley at least four products:(1) Pure barley (including No. 1 feed grade). (2) Barley containing 9 percent of an unspecified combination of oats, wild oats, wheat, or flax plus 1 percent coarse weed (no, 2 feed grade). (3) Barley containing 17 percent of an unspecified combination of oats, wild oats, wheat, or flax plus about 3 percent coarse weed seeds (no. 3 feed grade). (4) Barley as harvested on the farm.There is a further complication, in that the proportion of oats vs. wheat within tolerance of "other grains" may appreciably affect the feeding value of the barley, oats tending to reduce and wheat to increase the available energy of the final mixture.The Canadian grading scheme is of interest here only because it brings out clearly the difficulties of describing with any simple index the feeding value of a particular sample of a coarse grain. The variability in the purity of the barley is itself an important factor, and one that neither the name nor the usual chemical analysis defines. In addition, its protein may run from 9 to about 16 percent, its crude fibre from 2.5 to 8.5 percent, its weight per bushel from less than 40 to over 50 lb, and its TDN from 62 to 81 percent. With this range of variability, both botanical and chemical, it is not surprising that the performance of animals fed on rations composed chiefly of barley may not always be according to book specifications.All barleys are, nevertheless, energy feeds and as such are used in livestock rations primarily as sources of energy.As measured by the nutritional needs of animals, all barleys are deficient in salt, calcium, phosphorus, iron, iodine, and cobalt, and in vitamins A and D. Except for herbivorous animals, barley also requires supplementation with protein if it contains less than about 12 percent protein, and in all cases to improve its quality by increasing particularly the lysine content.There is no evidence that, once animals are accustomed to it, pure barley is less acceptable than any other entire cereal grain. Contamination with weed seeds will adversely affect its palatability, and use of such samples may explain the lower opinion some feeders have of barley than is justified by results with clean samples. Barley is frequently planted on wheat land that has become fouled with weeds, and among wheat raisers it is referred to as a cleaning crop. Thus, more weed seeds. Barley meal made from such tow-grade grain may be unpalatable, but this should not be changed to a characteristic of the barley itself.Nutritionally the limit of its inclusion in specific livestock rations is set only by the quantities of other products that must be included to make good the nutritional deficiencies of the barley, except that for very young animals it may be desirable in some way to reduce the hull of the ration either by coarse grinding and sifting or by dilution with low-fibre feeds.In practice, there are at least two uses to which barley is often put where the kind of other grain diluent may be of significance. When market pigs intended for lean bacon are finished on barley diluted with wheat, they tend to produce overfat carcasses. On the other hand, dilution of barley with oats tends to reduce the percentage of available energy and, consequently, tends to produce less fatterning. Similarly, non-producing stock being carried on maintenance rations can advantageously use the barleys of lower weight per bushel, such as oat or wild oat and light barley combinations.Finally, it may be in order to call attention to the black sheep of the barley family - a product officially designated as barley feed. It consists of the mill-run residue from the production of pot and pearl barleys. The residue is barley hull plus the outer layers of the kernel that are polished off the dehulled grain to get rid of the bran and embryo portions. This product is of low feed value, having at best only two-thirds the digestible nutrients of typical barley. This is mentioned because it is sometimes illegally incorporated into barley-containing meal mixtures. Its presence will lower the efficiency of the feed containing it, both by reducing the acceptibility of the ration to the stock and by reducing available energy.5.3.4 OatsWhat has been said concerning the variability of barley as harvested applies, in general, to oats as energy feed, the chief difference being that whereas barley normally contains about 6 percent crude fibre, oats contains 10 or 11 percent. Oats, in other words, has a lower energy value than barley. Variation between samples is fully as great as with barley, and the consequences of the differences in weight per bushel follow the same pattern as those described for barley. The botanical make-up of "as harvested" Canadian oats is shown in Table 19.Table 19 Botanical Make-up of "Oats" as Harvested Percent of wild oats and chaff Percent of wheat and barley Wheat: 0 Wheat: 5 Barley: 0 Barley: 5 Barley: 0 Barley: 5 Wild oats: 0 chaff: 0 45a 5 7 2 chaff: 5 9 2 2 Wild oats: 5 chaff: 0 11 1 3 chaff: 5 3 Wild oats: 10 chaff: 0 2 chaff: 5 a/ read as "45% of crop contained 0% wild oats, 07, wild oats, 0% chaff, 07, wheat, and 0% barley"There is no experimental evidence to support the contention put forward by some feeders that oats has any special nutritional virtue for any particular class of stock. It is true that the hull of the oat is somewhat softer and perhaps less irritating in the digestive tract then the hull of barley. Barley groats, oat groats, wheat, polished rice, and corn all are rich sources of available energy and have about equivalent feeding value in the ration. The chief differences in these grains as feeds are traceable to the proportions of the hull, more specifically, to the percentage of crude fibre.5.3.5 BuckwheatPerhaps the only other feed that requires special mention is buckwheat. First we should call attention to the problem of names of buckwheat products.The offal of buckwheat milling consists primarily of black hulls and middlings, the latter made up of the seed coat, the adhering endosperm, and the embryo. The hulls, which represent almost 30 percent of the weight of the entire buckwheat, have little feeding value. The middlings are rich in protein and fat, which are derived chiefly from the aleurone layers and the embryo, tissues. So-called buckwheat feed is a mixture of hulls and middlings. The proximate composition of these three products as given by Winton is in Table 20. We can see that entire buckwheat is an energy feed, buckwheat feed a roughage, and the middlings a protein supplement.The one particular feature that we should mention here is that products containing the hulls are likely to contain enough of a photoporphyrine to cause light sensitization in white-skinned animals. When exposed to the sun a rash may develop of such severity as to adversely affect the performance of the animals.Entire buckwheat is frequently incorporated into poultry scratch grain mixtures but is less often used for other classes of stock. Buckwheat middlings, however, is a common feedstuff in districts where buckwheat growing is a regular practice. The hulls, because of their woodly nature, are particularly indigestible and practically useless for feeding purposes.Table 20 Proximate Composition of Buckwheat By-products (All figures are percentages)WaterProteinFatFibreN-free extractAshEntire seed12.610.02.28.764.42.1Hulls6.57.81.433.647.13.6Middlings10.026.77.26.844.64.7Flour12.06.41.20.579.50.9Feed10.015.94.122.044.83.25.3.6 Wheat bran and other wheat milling by-productsWheat bran has had a rather checkered career as a feedstuff. Originally discarded as a worthless offal from the milling of wheat for flour, it was suggested and eventually popularized as a livestock feed. Its light, bulky nature, its 16 percent high-quality protein (a chemical score equal to that of beef muscle), and its high phosphorus content give bran a unique place in livestock feeding. About 40 percent of the wheat germ is in the bran, which accounts for its high-quality protein. Included in the herbivore ration, it provides supplementary phosphorus to correct the common shortage in the forage, and its cellulose-hemicellulose carbohydrate is an acceptable source of energy for these animals. Its bulk is often advantageous as a means of lightening a predominantly corn ration.The bulkiness of bran is of special usefulness in the preparation of non-fattening rations, as for the bacon hog, to whom bran yields less energy than to cattle. Thus its introduction-into the meal mixture of market pigs during the last two months of feeding before slaughter curtails the energy intake and the fattening of the pig, without restricting the feed. Canadian experiments and practical experience have demonstrated that hog-finishing rations diluted with 25 percent wheat bran by weight can be self-fed to market pigs without leading to the excessively fat carcasses which otherwise result from self-feeding practices.6. PROTEIN SUPPLEMENTS 6.1 Products of Plant Origin 6.2 Protein Supplements of Animal and Marine Origin
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