Chapter 3 Feedstuffs.
GRAIN MERCHANT, LATE 1800S
Many types of feed ingredients or feedstuffs are available to supply the nutritional needs of livestock. These feedstuffs are the raw materials that are converted into animal cells, tissues, organs, and products. A familiarity with the chemical and nutritional composition of the various classes of feedstuffs is essential in order to formulate the most economical and profitable rations. It is also important to be familiar with the various feedstuff types to plan for planting, harvesting, and storage of homegrown feedstuffs. Proper preservation of stored feedstuffs is a critical profitability factor for some types of farms and ranches.
CLASSIFICATION OF FEEDSTUFFS
A feedstuff is loosely defined as any component of a ration that serves some useful function. Feedstuffs generally are included in the ration to help meet the requirement for one or more nutrients. However, they may also be included in the ration to provide bulk, reduce oxidation, emulsify fats, provide flavor, improve animal health, or improve characteristics of the products produced by livestock.
Because there are thousands of feedstuffs used in the formulation of livestock rations, a discussion of feedstuffs must be made on the basis of groups or types of feedstuffs with common characteristics. The National Research Council (NRC) has established such groups in developing its feedstuff numbering system (National Research Council, 1972).
In the NRC system a 6-digit number, the International Feed Number (IFN), is used to identify feedstuffs. The first digit in the IFN identifies the feed type as one of the following:
1. Dry forages
2. Pasture, range plants, and feeds cut and fed green
4. Energy concentrates
5. Protein supplements
The remaining five digits in the IFN are unique to the feedstuff and may be used to identify it in databases used in research (Table 3-1).
It is important to realize that the classification of feedstuffs into categories is imprecise because most feedstuffs are complex packages of multiple nutrient sources. For example, the same feedstuff may legitimately be considered either an energy feed or a protein supplement, or even a forage. For this discussion, we will use the categories identified by the first digit in the IFN and include a few subcategories.
1. Dry forages
2. Pasture, range plants, and feeds cut and fed fresh
* Hay crop silage
* Small grain silage
* Corn and sorghum silage
4. Energy concentrates
* Cereal grains
* Residues from the sugar and citrus industries
* Fats and oils
5. Protein supplements
* Plant protein sources
* Animal protein sources
* Nonprotein nitrogen sources
6. Mineral supplements
7. Vitamin supplements
In the NRC system, categories 1 through 3 include forages. These forage categories differ as to whether the crop is preserved or fed fresh, and if preserved, how. The term roughage is synonymous with the term forage, but because the term roughage has a somewhat negative connotation ("rough"), it has fallen out of favor with many nutritionists. Most feedstuffs classified as forage are bulky, high-fiber feedstuffs that have a low weight and low nutrient content per unit of volume. Though some forage is essential for the health of herbivorous animals, productivity on an all forage diet is usually too low to be profitable.
The protein, mineral, and vitamin content of forages varies greatly. Legumes may contain 25 percent protein. Other forages such as straws may have only 5 percent crude protein. Mineral content is also highly variable. Most forages, particularly legumes, are relatively good sources of calcium. Phosphorus content is moderate to low and potassium content is high relative to the requirement for most animals. Magnesium content of forages is usually good but under certain circumstances, animals on high-forage diets can experience magnesium deficiency. The trace minerals vary greatly depending on plant species, soil, and fertilization practices.
A number of factors may affect forage composition and nutritive value.
1. Maturity has one of the most pronounced effects. As a forage plant matures, the protein and soluble carbohydrate content decline whereas the fiber and lignin content increase. Lignin is not only indigestible itself, but also has an encrusting effect that reduces digestibility of otherwise digestible plant cell components. The presence of lignin greatly limits plant digestibility.
2. Soil fertility, fertilization, and weather are known to have a pronounced effect on quantity of forage produced. Quality of the forage may also be affected by these factors.
3. Harvesting and storage methods can have a significant effect on nutrient value of forage. For example, harvesting techniques that result in significant leaf loss will reduce the nutrient content of the feedstuff. Grasses The grasses include all of the wild and cultivated species used for grazing, as well as the cultivated cereal grain species. However, this section will be concerned only with grass as a forage. The discussion will be general because of the tremendous variety of grasses.
In comparison with legumes of similar maturity, the protein and calcium content of grasses is nearly always lower. The variation in other nutrients is such that none is consistently higher in either type of forage (Table 3-2).
Grasses may be classified as cool season (temperate), warm season, or tropical. Cool-season grasses grow rapidly during the cool, moist seasons of the year, and become dormant during the hot, dry seasons. Warm-season grasses grow during the hot seasons and become dormant during the cool seasons. Cool-season grasses generally mature at slower rates and deteriorate in quality less rapidly than do warm-season grasses. Tropical grasses are adapted only to tropical climates where freezing temperatures do not occur.
Some of the more commonly used cool-season grasses are ryegrass, orchardgrass, reed canarygrass, tall fescue, timothy, and smooth brome grass. Some of the more commonly used warm-season grasses are Bermudagrass, Johnsongrass, Bahiagrass, Dallisgrass, Switch grass and the Bluestem grasses.
The grasses that are cultivated for their cereal grains are also used as forage sources in pasture. Examples include barley, oats, winter wheat, and rye. These species can be used for pasture during the winter and early spring with minimal effect on grain yield.
Alfalfa is the most common legume used for pasture, hay-crop silage, and hay. It is known as lucern in most English-speaking areas other than North America. The clovers are also legumes that are extensively used in animal diets. Common clovers include ladino, red, white, alsike, sweetclover, and subterranean clover. Lespedeza, crown vetch, kudzu, and birdsfoot trefoil are other legumes that may be fed to animals.
Through an association with bacteria in the root nodules, legumes are able to "fix" nitrogen from the atmosphere. This means that legumes can make the protein in their tissues from nitrogen in the air rather than from nitrogen in the soil. In legumes, atmospheric nitrogen is reduced to ammonia, which is used to manufacture amino acids. The amino acids are used in plant protein synthesis.
Some legumes, particularly alfalfa and white, ladino, and red clover, are prone to cause bloat in cattle. Bloat is caused by foam-producing compounds such as cytoplasmic proteins and pectins. Foam at the base of the esophagus inhibits the eructation mechanism leading to the accumulation in the rumen of normal rumen gases. As the rumen swells and pressure increases, expansion of the thoracic cavity during inhalation becomes difficult. Without relief, suffocation and/or heart failure will occur. Additional information on bloat is found in Chapter 16.
Native Pastures and Range Plants
Uncultivated native pastures and rangeland account for many millions of acres of land where the topography, soil, or environment is unsuited to intensive agricultural methods. These areas contain a wide range of grasses, sedges, forbs, and browse.
Miscellaneous Forage Plants
The forages used in livestock diets are chosen because they are available, they have good nutrient content, and they yield well as a crop. Nontraditional crops may become useful as forages, depending on the farm and the year.
The tops of root crops such as beets and turnips have been used successfully. Plants in the cabbage family, including kale cabbage and rape, have also been used as forages in livestock diets. Rape is sometimes planted for use by sheep as fall pasture.
Toxins in plants
Under certain conditions, some plants may accumulate toxins in their tissues. Generally, livestock will avoid such plants. However, especially during times of feed shortage, livestock may ingest toxic plants. Tables 3-3 through 3-5 list some of these plants and their toxins. The toxins that may be ingested by grazing livestock and their effects on these animals has been recently reviewed (Cheeke, 1995).
Hay Haymaking has been practiced for many centuries as an effective method of conserving forage crops. With the development of newer methods of forage preservation, the importance of haymaking has declined in recent years. However, the form of hay is unique among feedstuffs. Its length and bulkiness are useful in maintaining the digestive health of herbivores, especially in highgrain diets.
The goal of making hay is to preserve the forage by making it dry enough through the curing process so that molds cannot grow and the enzymes of spoilage bacteria cannot function.
Both the quality and quantity of field-cured hay depends on plant maturity when cut, method of handling, moisture content, and weather conditions during harvest.
Hay should be harvested at the stage of maturity that will provide a maximum yield of nutrients per unit of land without causing damage to the next crop. The maturity stages for legumes are vegetative, bud, bloom, and mature or seed stage. The maturity stages for grasses are vegetative, boot, head (containing the blooms), and mature or seed stage. For practical nutrition purposes, the most commonly recommended stage of maturity to cut legumes and grasses is when blooms first begin to appear. For both legumes and grasses, cutting later than the recommended time results in more yield but poorer quality. Cutting earlier results in less yield but higher quality, and runs the risk of damaging the plants, particularly legumes.
During the curing process, the moisture content is reduced, thereby increasing the dry matter content. Moisture content of fresh herbage will range from 75 to 90 percent (dry matter content from 10 to 25 percent). The moisture content of the cured hay must be no more than 20 percent (dry matter no less than 80 percent) to ensure that it can be stored without marked nutritional changes. A microwave oven can be used to determine the moisture content of the curing hay crop as follows:
1. Take a sample from your hay swaths and cut into half-inch pieces.
2. Weigh out a sample of about 100 g. Record the exact weight and identify it as the wet weight.
3. Spread the sample on a microwavable plate.
4. Place the plate of sample and a glass of water in the microwave (the water is to prevent the sample from catching fire).
5. Microwave for 3 minutes.
6. Reweigh the sample and record its weight. Stir the sample.
7. Return the sample to the microwave and microwave for 1- to 2-minute intervals. Record the weight, stir, and return to the microwave.
8. Repeat step 7 until the sample looses less than 1 g between heatings. This weight is the dry weight.
9. Calculate the percent moisture content as follows:
[(wet weight - dry weight)/wet weight] x 100 = moisture percentage
10. Calculate the percent dry matter content as 100 - (step 9).
Typical losses of hay crop dry matter from cutting to feeding are 20 to 30 percent (Undersander et al., 1994). The losses in hay making are generally associated with harvest activities and include shattering and bleaching. As hay sits in the windrow, it dries or cures unevenly. The leaves dry faster than the stems, and will tend to become brittle and may fall off. This is called shattering. Because most of the nutrition in hay is found in the leaves, harvesting procedures that result in shattering will reduce the nutritive value of hay. Bleaching is the term that describes hay that is overexposed to the sun. Bleaching results in loss of vitamin value. If cured hay is rained on, the hay may lose a considerable amount of its original nutritive value as the water leaches out soluble nutrients. Rain on freshly cut hay will cause little damage.
There are various principles and techniques that may be used to minimize harvest losses in hay making. Rapid drying of the cut crop ensures minimal nutritive losses. Slow drying is frequently accompanied by mold growth, which reduces palatability and nutritive value. Slow drying may also lead to a reduction in nutrient value due to the activity of plant enzymes and microorganisms or oxidation. Crimping, to crush the stems of plants, speeds up the drying process. For legumes, drying agents are available that remove the waxy cutin layer, hastening water loss. Adding preservatives such as propionic acid to the cut crop makes it possible to bale hay at a higher moisture content (25 to 30 percent). This can help with the harvest in difficult weather and will minimizing shattering.
In field-curing hay, some loss of leaves should be expected due to shattering. Dehydration is an alternative to field-curing hay that minimizes the losses due to shattering. The crop is harvested wet and moved into a dehydrating facility. Dehydration is practiced in the United States and some areas of Europe. In the United States, alfalfa is the primary crop that is dehydrated, but in Europe, grasses or grass-clover mixtures may be used. In dehydrating alfalfa, the herbage is cut, usually at prebloom, dried quickly, ground, and sometimes cubed or pelleted.
Hay is stored in cubes, bales, or stacks. Hay cubes are made by compressing long or coarsely chopped alfalfa hay. Usually, an edible glue or binder is added to make cubes approximately 11/4 to 2 inches on a side. Hay cubes have a density of 30 to 32 lb./ft3. Because of their high density, a given storage space will be able to hold more tons of hay in the form of cubes than in any other form. Cubes may be more convenient to handle and feed than other hay packages. Though hay in cubed form is usually the most expensive way to feed hay, cubes may result in reduced wastage.
Long hay is packaged in bales or stacks. Bales come in many different sizes and shapes from the 40-lb. square bale to the round bales that weigh from 400 to 1200 lb. or more. Stacks are made by hydraulically compressing hay. Hay stacks generally weigh from 1 to 6 tons.
Once in the cube, bale, or stack, hay stored properly will maintain its nutritive value for years. However, hays that are stored too wet may lose nutritive value due to microorganism activity. Microorganism activity in wet hay reduces nutritive value in three ways:
1. Microorganisms use up nutrients.
2. Microorganisms may produce toxins.
3. Microorganisms generate heat, which may reduce nutrient availability.
If enough heat is generated, spontaneous combustion could occur.
Crop Residues Straw is a poorly digested, low-nutrient content crop residue. It consists mostly of the stems that remain after the removal of the crop's seeds. The primary supply of straw comes from wheat, barley, rye, rice, and oats, but in some areas substantial amounts may be available from the grass or legume seed industry, and from other miscellaneous crops. The nutrient content and palatability of straw is low, and this limits its use in livestock diets.
Other crop residues include corn cobs, stover (corn or sorghum stalks and leaves), sugarcane bagasse, and hulls of cottonseeds, peanuts, and soybeans. Crop residues such as straw and hulls consist of the nonliving cell wall portion of the plant and, therefore, contain little of the nutrients found inside cells. In addition, the cell wall of these crop residues is usually highly lignified, meaning that the cell wall constituents are encrusted in indigestible lignin, rendering them inaccessible to microbial enzymes.
There are various chemical treatments that are capable of dissolving lignin to improve the digestibility of highly lignified crop residues. Sodium hydroxide and ammonia treatments (such as ammonium hydroxide and gaseous ammonia) are effective in dissolving lignin to increase the digestibility of cell wall constituents. Ammoniated hay toxicosis (bovine hysteria, bovine bonkers, crazy cow syndrome) is a health problem that occurs if a toxin is produced during ammoniation. This toxin is produced when reducing sugars such as glucose react with ammonia in the presence of temperatures in excess of 158[degrees] F (Perdok & Leng, 1987). Symptoms include hyperexcitability, incoordination, tremors, and convulsion.
Pasture, Range Plants, and Feeds Cut and Fed Fresh
Pasture and range, like dry forage, may consist of native and/or cultivated species, the latter used to improve productivity or versatility. The use of pasture and range allows grazing animals to harvest the forage and spread the manure. Animals on pasture or range should have access to water, shade, and a mineral mix containing salt and the mineral nutrients in which the pasture is deficient.
Range The western U.S. rangelands are vast areas used for grazing livestock. They differ from pastures mainly in size and in the fact that much of the rangeland is on public lands.
Pasture The primary incentives to use pasture are the following:
1. Less labor may be required feeding livestock pasture forage compared to green chop or preserved forages
2. The possibility that pasture is cheaper to produce than hay, silage, or green chop
3. A possible marketing advantage for pasture-fed livestock
4. Some lands may not be useful agriculturally except as pasture
However, the use of pasture does bring with it some management challenges, five of which are described below.
1. Nitrate poisoning may occur in animals grazing on grasses that have been heavily fertilized with nitrogen-containing fertilizers.
2. When ruminant animals (and on rare occasions, horses) have been pastured for some time exclusively on lush spring pasture, they begin to lose coordination and may undergo sudden convulsive seizures. This is called grass staggers or grass tetany. It is caused by a magnesium deficiency. To avoid this problem, animals grazing spring pastures should be provided with a mineral supplement containing a source of magnesium. Grass tetany is discussed in Chapter 9.
3. Early in the growing season, grasses--especially cool season grasses--have a very high water content and an excess of protein for most grazing animals. The result is that the pastured animals often have "loose" manure or diarrhea.
4. Lactating dairy cows on pasture usually lose weight and will be unable to consume the pounds of pasture needed to deliver the energy to support high production. There are four reasons for this.
a. The high water content of pasture makes it very dilute in nutrient content.
b. Pasture is not a high-energy feedstuff. Because pastured animals spend much of the day on pasture, it is difficult to supplement their diet with high-energy feedstuffs.
c. Grazing requires the animal to do the harvesting that uses up feed energy.
d. Much of the high protein of lush pasture needs to be processed and eliminated by livestock. This processing activity uses energy that exacerbates the energy shortage. Table 3-6 illustrates why concentrated energy sources are needed to create rations that can support high production.
5. The pasture represents just the forage component of the diet, and its nutrient profile is lacking in more than just magnesium and energy for high-producing animals. Animals with high production potential or the potential for rapid gains will not realize their potential when on pasture because the feeder has limited control over the animals' diet.
In spite of the challenges involved when attempting to incorporate pasture in a balanced ration, pasture can be an economical component of livestock diets.
Pasture Management All systems of pasture management are centered on the principle of controlling the frequency and severity of defoliation of individual plants. This control is exercised by management of stocking rates and the intensity and frequency of grazing. Pastures may benefit from periodic mowing. Mowing helps limit the growth of undesirable plants that have been avoided by livestock and can help maintain desirable plants in a vegetative, high-nutrient content stage of growth.
Continuous grazing is essentially unmanaged pasture. It involves stocking a pasture with animals continuously. Continuous grazing is the least costly method of pasture management, but results in the least amount of nutrient intake from pasture plants. Animals on a continuously grazed pasture avoid the plants around manure, overgraze some areas of the pasture while avoiding others, and may eat only the most palatable portions of nutritious plants. This method of pasture management makes it difficult to take maximum advantage of pasture as a source of nutrients for livestock.
Rotational grazing involves fencing off the pasture into paddocks. Animals are moved through the farm's different paddocks, allowing each paddock's forage time to recover before the animals return. When moving animals through the paddocks, it may be useful to know that animals, especially sheep, usually prefer to graze into the wind. The combination of high stocking density and short access time (usually 1 to 4 days) characteristic of rotational grazing prevents the problem of selective grazing. Rotational grazing allows the producer to effectively utilize pasture as a source of nutrients for livestock.
The daily forage allowance (DFA) is useful in predicting how much pasture will be eaten by grazing animals in an intensively managed system. Pasture consumption is a function of the pasture dry matter available, relative to the animals' potential pasture dry matter intake. The DFAis expressed as multiples of the potential dry matter intake of the herd. A DFA of 2 means that the herd has available twice what it could potentially eat in pasture dry matter (Figure 3-1). The companion application to this text for beef uses a value referred to as daily forage grazed (DFG). This differs from the DFA in that it is the forage available expressed as tons/acre, dry basis, rather than as multiples of potential dry matter intake.
Figure 3-1 Calculating the DFA Given: Initial pasture mass (lb. dry matter/acre): 1250 Paddock size (acres): 25 Potential forage dry matter intake/animal (lb.): 30 Number of animals: 80 Number of days in the rotation: 6 DFA = (1250 x 25) / (30 x 80 x 6) = 2.2
The initial pasture mass (IPM) is expressed in pounds dry matter per acre, and can be estimated from hay harvesting experience, clippings, or calibrated measuring devices. In well-managed pastures, the IPM can also be estimated from the plant height. Legumes contain about 120 lb. dry matter per acre per inch of plant height. Well-managed grass pastures contain about 250 lb. dry matter per acre per inch of plant height. An orchardgrass pasture that has grown to 8 in. in height contains about 2,000 lb. of dry matter per acre (250 x 8).
Using Table 3-7, an adjustment factor can be found that may be applied to the animal's predicted pasture dry matter intake. As can be seen in Table 3-7, pasture dry matter intake declines with reduced pasture dry matter available and with reduced daily forage allowance. When pasture dry matter intake declines, performance will decline unless supplemental feed is provided or animals are moved to a new pasture.
Mixed Livestock Grazing Because herbivores differ in their grazing habits, different species grazing the same pasture may not be directly competitive. Simultaneous grazing of sheep and cattle may result in higher yields of animal products per unit of land area than single-species grazing (Nolan & Connolly, 1989). Mixed livestock grazing also may help maintain beneficial forage species on pasture (Abaye, Allen, & Fontenot, 1997).
Green Chop Green chop, sometimes called soilage, is herbage that has been cut and chopped in the field and fed fresh to livestock in confinement. Plants used in this manner are forage grasses, legumes, sudan grass, the corn plant, and residues of food crops used for human consumption.
A major advantage of green chop is that more usable nutrients can be salvaged per unit of land than by other methods such as pasturing, haymaking, or ensiling. A major disadvantage of green chop is the labor required; the herbage is not preserved and must be harvested and fed daily to maintain its palatability and nutritive value. When growth outruns daily need, it may be necessary to mow the crop to maintain quality.
Types of crops made into silage
Hay crop silage The primary reason for choosing to store the hay crop as silage rather than hay has to do with the labor necessary to feed the crop. Feeding the hay crop as silage requires less labor than would feeding the hay crop as hay. Weather also may be a factor involved in choosing to make silage or hay: dry hay requires more drying time than hay crop silage. There are also significant differences in the storage facilities needed.
Good silage is equally palatable to good hay, and it is well utilized. This has been verified in all species of livestock. In addition to other advantages, the fermentation process will reduce the level of some toxic substances in the fresh crop.
Silage is produced by fermenting high-moisture herbage. The goal of making silage is to turn enough carbohydrate into acid during the fermentation process so that the pH of the silage prevents the growth of spoilage bacteria. A silo is used to create the anaerobic environment necessary for fermentation to occur.
There are several different types of silos. The general categories of silos are tower or upright silos, horizontal silos, bag silos, and stack silos. Tower silos may be of the conventional type, usually made from concrete staves or poured concrete with a roof. Tower silos also may be constructed of protected metal or fiberglass. Horizontal silos may be of the bunker type that have concrete walls and (usually) a concrete floor, or they may be of the trench type (a simple excavation with a sloped floor to permit drainage). Both types of horizontal silos should be covered with heavyweight (6 mm) polyethylene (plastic) film that is securely held down to reduce surface spoilage. Polyethylene tubes, packed with silage and sealed at each end, may be used as a silo. The capacity of these tubes depends on the diameter of the face of the tube. A tube that is 12 ft. in diameter holds approximately 2 tons (as fed) per linear foot. Properly used, these tubes produce excellent quality silage although they are not reusable and bag disposal may be a problem. Stack silos are essentially a packed pile of silage covered with a polyethylene film that is held down.
In preparing the hay crop for the silo, the crop must be wilted and chopped. Recommendations for maturity, dry matter content, and chop length for crops to be ensiled are given in Table 3-8. Wilting is the term used to describe the process of drying the hay crop to a level suitable for ensiling, usually 30 to 40 percent dry matter (60 to 70 percent water). Moisture must be reduced if the acid produced from carbohydrates during fermentation is to reduce the overall pH effectively. The fresh cut crop will have 75 to 90 percent moisture. The proper level for ensiling depends on the crop, the chop length, and the silo type. Hay crops to be ensiled must be reduced to lower water content than corn and small-grain crops because hay crops contain less fermentable carbohydrates.
The dry matter content of the hay crop to be ensiled can be measured using a microwave oven in the same was as described for hay. The "grab test" is a method to estimate moisture content of the hay crop (Figure 3-2).
As can be seen from Figure 3-3, drying the hay crop results in significant harvest losses. As discussed earlier, these losses are due to leaf loss or shattering. Because silage is harvested at a higher water content than hay, shattering is not a problem.
Packing silage is essential to minimize oxygen for effective fermentation. Chop length and moisture content both affect ease of packing. Higher moisture content makes it easier to pack, as does smaller chop length.
A third variable that affects packing and oxygen exclusion is silo type. In all types of upright silos, packing is facilitated by the physical weight of the column of silage. The expensive sealed silos are effective in excluding oxygen, and it is possible to use larger chop length and/or lower moisture contents for silage going into these silos. Packing effectiveness in the horizontal silo depends on silo management. A little higher moisture in the crop can assist packing in this type of silo. Bag silos provide a good environment for fermentation and will produce good silage if properly managed.
[FIGURE 3-2 OMITTED]
[FIGURE 3-3 OMITTED]
Whereas the primary losses in hay making occur during harvest, the primary losses in silage making occur during storage. These losses are discussed later in this chapter under "The Fermentation Process."
Small grain silage Silage may be made from the whole plant of crops otherwise grown for their grain. Examples of small-grain crops used for silage include oats, barley, sorghum, and wheat. General recommendations for these crops are to cut when the seed is in the milk to soft-dough stage.
Corn and sorghum silage Most silage in the United States is made from the whole corn plant and from a number of sorghum varieties. Observations of the corn kernel's milk line can be useful, in conjunction with whole plant dry matter testing, to help determine when the corn crop is at the appropriate stage for ensiling. The milk line is a line that appears on the kernel at the junction between the solid and liquid phases. As the plant matures, the solid phase expands, moving down the kernel toward the cob (Figures 3-4 and 3-5). Concurrently, the plant's overall moisture content decreases. The proper dry matter level for harvest and ensiling roughly corresponds to a kernel milk line of 1/2 to 2/3 the way down the kernel. There will be significant variation among hybrids as to how milk-line position relates to whole plant percent dry matter content, and milk-line observations should be made in conjunction with whole plant dry matter testing.
Corn and sorghum silages are fed as forage sources. The lower the lignin content of the forage, the higher the digestibility of the forage's fiber carbohydrate, measured as neutral detergent fiber (NDF). The formula relating lignin to NDF digestibility is shown in Chapter 4 and in the dairy application's feed table as a comment behind the NDF digestibility column title. A trait found in both corn and sorghum crops called brown-midrib (BMR) is associated with low lignin content. Studies have shown improved growth (Colenbrander, Bauman, & Lechtenberg, 1975) and lactation (Frenchick, Johnson, Murphy, & Otterby, 1976) performance when using silages with the BMR genotype. However, BMR corn shows reduced grain yield over non-BMR corn. If it is not known at planting whether the corn crop will be used for silage or grain, BMR corn should not be planted. There appears to be no reduction in grain yield associated with the BMR train in sorghum (Cherney, 1991).
[FIGURE 3-4 OMITTED]
[FIGURE 3-5 OMITTED]
Miscellaneous silages Other materials have been used to make silage. Waste from food crops such as sweet corn, green beans, green peas, and potato tubers are examples. Ensiling such feedstuffs is advantageous in that it results in a more uniform feed and a known supply, and the feedstuff is preserved.
The fermentation process Once in the silo, the fresh crop will undergo changes as a result of the activity of plant enzymes and the microbes that are present on the crop in the field or that find their way into it from other routes. The plant enzymes continue to be active for the first few days after cutting, resulting in some loss of carbohydrate and protein. Plant proteins are partially broken down by cellular enzymes, resulting in an increase in nonprotein nitrogen (NPN) compounds such as amino acids. Proteins are also fermented by microbes to the gasses nitrogen tetraxide, nitrogen dioxide, and nitric acid. These gasses are highly toxic to humans. In tower silos, these gasses accumulate to dangerous levels for 3 weeks following the filling of the silo. As carbohydrate is oxidized by aerobic microorganisms and plant enzymes to C[O.sub.2] and water, heat is generated. Under normal conditions, temperatures during fermentation will peak 10[degrees] to 15[degrees]F above ambient temperature. Excessively high temperatures will result in damage to the feed protein, reducing the amount available to the animal. Heat damage can be minimized by ensuring that the crop is well packed to exclude air.
Anaerobic microorganisms become active after the oxygen in the silage has been depleted. Anaerobic microorganisms multiply rapidly, using sugars and starches, and producing lactic acid with lesser amounts of acetic, formic, propionic, and butyric acid. However, little butyric acid is present in well-preserved silage. Continued action occurs on nitrogen-containing compounds with further solubilization and production of ammonia and other nonprotein nitrogen compounds. The level of lactic acid rises in well-preserved silage, eventually reaching levels of 7 to 8 percent and the pH drops to about 3.5 to 4.0, depending on buffering capacity and dry matter content of the crop. Figure 3-6 presents a time line of events postensiling.
If the silage is too wet or the supply of fermentable carbohydrates too low, the pH will not drop to an acceptably low level. This will allow the Clostridia bacteria to become active, producing butyric acid and new compounds with foul odors and potentially toxic characteristics.
On the other hand, if the mass is too dry or poorly packed, the abundant oxygen present in the silage will lead to excess heating and mold growth resulting in reduced recovery of silage dry matter, nutrient losses, reduced palatability and sometimes the elaboration of toxic compounds. The amount of packing necessary depends on forage characteristics, filling rate, the tractor weight used in packing, and packing technique. The relationships between these factors have been investigated (Ruppel, Pitt, Chase, & Galton, 1995). Unavoidable losses from ensiling Some nutrient losses are unavoidable when making silage. Respiration of the live plant cells shortly after the material is placed in the silo is unavoidable. Respiration depends on the presence of oxygen so this loss should be minimal if the silage is packed well and if the silo is reasonably air-tight.
Like respiration losses, some fermentation losses are unavoidable. The lactic acid that will eventually preserve the silage is produced from the fermentation (loss) of some carbohydrate.
Avoidable losses from ensiling Some types of silage nutrient losses are avoidable. Where dry matter content of the silage is less than 30 percent (water content is greater than 70 percent), water will seep down through the silage and drain away from the silo. This seepage is rich in nutrients and constitutes not only a loss in terms of silage quantity and quality, but also is a potentially powerful pollutant if allowed to drain into a stream or wetland. Excessively wet silage also may undergo butyric acid fermentation, which further reduces the quality and quantity of the silage.
Another avoidable loss in silage making is mold growth. Mold requires oxygen and water to grow, but mold growth is discouraged by acid. Silage will be free from mold only as long as the acid level remains high and the oxygen level remains low. The three feed-related problems associated with mold growth are (1) the mold organism uses up nutrients, (2) moldy feed is unpalatable, and (3) the mold organism may produce mycotoxins. The presence of mold does not guarantee that there are mycotoxins present, and mycotoxins may be present even if there is no visible mold. Some mold nearly always grows around the perimeter and on top of the silage because it is difficult to eliminate oxygen from these areas. The moldy feed should be discarded. This chore requires respiratory protection because of the risk of developing farmer's lung disease, an allergic reaction to the mold. Further discussion of mold growth in feedstuffs is found in Chapter 13.
[FIGURE 3-6 OMITTED]
Phases of silage fermentation
* Material placed in silo
* Plant cells use up trapped oxygen--respiration
* [C.sub.6][H.sub.12][O.sup.6] + 6[O.sub.2][right arrow]6C[O.sub.2]6[H.sub.2]O + 673 calories
* Some protein ??NPN
* Anaerobic microorganisms begin to function
* Produce acetic acid from carbohydrate; pH drops to 4.2
* Acetic acid producers cease to function
* Lactic acid producers begin to produce lactic acid from carbohydrate
* Occurs 3 to 5 days after filing silo
* Lactic acid accumulates
* pH drops
* Temperature cools
* Final pH 3.5 to 4.0
* Microorganisms cannot attack silage
* If enough lactic acid has accumulated, stable storage is achieved 15 to 21 days after filling silo
Silage additives Silage additives are designed to improve the efficiency of silage fermentation. The decision as to whether to use an additive should be based on the demonstrated effectiveness of the additive, its cost, the existence of a clear need for the additive, and practicality in the use of the additive. For the most part, additives target either Phase 3 or Phase 4 of the fermentation process.
Phase 3 depends on adequate fermentable carbohydrate for the lactic acid-producing bacteria. Fermentable carbohydrate within the crop varies with the weather. Exposure to the sun increases the fermentable carbohydrate content in the living plant; ideally, the timing of harvest should be made with this in mind. Additives that have been used to increase the fermentable carbohydrate in the silage include cracked corn at 100 to 150 lb./ton of silage and molasses at 40 to 80 lb./ton of silage.
Phase 3 also depends on the presence of adequate numbers of lactic acid-producing bacteria. Microbial numbers are reduced in cool temperatures to a point at which silage fermentation may be negatively impacted. Many microbial additives or inoculants are available to help with silage preservation. These inoculants generally contain Lactobacillus plantarum microbial strains that have improved efficiency over naturally occurring microbes in generating lactic acid.
Phase 4 requires enough acid to lower silage pH. Organic acids such as propionic acid at 1 percent have been used successfully as silage preservation aids.
Other products are sometimes added to silage to improve its various characteristics. Limestone and urea have been added to corn silage to improve the nutrient value of this feedstuff. Certain enzymes added to silage will improve feed value, and work is underway to improve the performance and cost effectiveness of these products.
Problem 1: Heat damage indicated on forage analysis
* Caused by the presence of oxygen
** poor packing
** holes in silo
** slow filling
** haylage on top of corn silage or vice versa
Problem 2: Mold growth
* Caused by the presence of oxygen (see Problem 1)
Problem 3: Sour smell, slimy feel to the silage
* The acid generated was not sufficient to lower the overall pH, and clostridial organisms have begun to attack the silage in a butyric acid fermentation.
** Problems 4 and 5 will also be evident
Problem 4: Silage feeds out hot
* Poor initial fermentation--too wet
* Oxygen exposure after feedout started
** feedout too slow/silo too big (see Sizing Bunker Silos)
** face of bunker has too much exposed surface area; as you remove silage, keep the face vertical
* Warm weather
** this accelerates feed deterioration and may be the cause of the problem
Problem 5: Silage becomes hot after unloading
* Poor initial fermentation--too wet
* Feed bunk not clean before filling bacteria and mold become active
* Warm weather
* Other ration components may be bad (wet brewer's, other wet feeds)
* Soil, manure contamination
Problem 6: Excess surface spoilage at opening of silo
* Some spoilage is difficult to prevent along the perimeter and surface of the silo
** minimize surface spoilage by covering the silo with a 6-mm polyethylene sheet and cover this with tires
** use 20 to 25 tires per 100 sq. ft. This generally means tires should be touching each other over the silo surface
Differences between hay crop silage and corn silage Density
* Corn silage density is approximately 40 to 45 as fed lb./[ft.sup.3] or about 14 dry matter lb./[ft.sup.3].
* Hay crop silage is lower in density--approximately 35 to 40 as fed lb./[ft.sup.3] or about 14 dry matter lb./[ft.sup.3].
* Corn silage is harvested once per year and a silo is needed that will hold a full year's inventory. Hay crop silage is harvested in multiple cuttings and, therefore, it is not necessary to have a silo available that is capable of holding a full year's inventory.
Keeping silage fresh in a bunker silo
* After feedout has begun, the silage surface or face is exposed to oxygen, which will begin to deteriorate the silage. It is necessary to remove a sufficient layer of silage each day to get to silage that has not yet begun to deteriorate. Because the corn plant, at the recommended stage for ensiling, has more fermentable carbohydrate than does the hay crop at the usual stage for ensiling, corn silage is generally more stable than hay crop silage. A removal rate of 4 to 6 in. daily is usually enough to ensure fresh corn silage at each feeding. For hay crop silage, it is recommended that 6-9 in. be removed daily, and more may be necessary in hot weather. Achieving the proper removal rate with a given number of livestock means sizing the silo properly.
Sizing bunker silos
* Silage density (lb./[ft.sup.3])
** a typical value is 14 lb. DM/ft3
** for our example, we will use corn silage with a percent DM of 31 percent. The pounds per cubic foot, as fed basis is, therefore, 14/0.31 = 45.
* Side walls
** decide how high you want the walls; as an example, use 12-ft. walls
* Daily use: for our example, we will use:
** 250 lactating cows x 35 lb./cow = 8,750 lb./day
** 15 dry cows x 20 lb./cow = 300 lb./day
** 175 heifers = 10 lb./heifer = 1,750 lb./day
** total daily use = 8,750 + 300 + 1,750 = 10,800 lb. daily silage use
* Annual use
** 10,800 x 365 = 3,942,000 lb. annual silage use
* Spacing of walls
** some silos have sloped sidewalls
** to get the surface area of the silo face, you need a width measurement
** use the average between the width across the bottom of the walls and the width across the top of the walls. We will use a value of 40 ft.
* Surface area of the face
** 40 ft. wide x 12 ft. high = 480 sq. ft.
* If you removed 12 in. from the face, how many pounds of silage in cubic feet would you take? Our corn silage is 45 lb./cu. ft.
** 480 sq. ft. x 45 lb./cu. ft. = 21,600 lb.
* If you removed 6 in. from the face, how many pounds of silage would you take? Daily use of 6 in. is enough to keep corn silage fresh.
** 21,600/2 = 10,800 lb. This matches our daily use.
* With 12-ft. sidewalls spaced at 40 ft., how long would this silo have to be to hold a year's inventory? Annual use is 3,942,000 lb. One cubic foot of silage holds 21,600 lb.
** 3,942,000 lb./21,600 lb./ft. _ 182.5 ft. long.
Images and supplemental information on energy concentrates are found in the file titled Images.ppt on the text's accompanying On-Line Companion. To view this file please go to http://www.agriculture.delmar.com and click on Resources. Click on On-Line Resources and select from the titles listed.
Feedstuffs classified as energy concentrates are those that are added to a ration primarily to increase energy density. Included are the cereal grains, some of their milling coproducts, some types of liquid feeds such as molasses, and the fats and oils. High-energy feedstuffs generally have low levels of protein. However, the high-protein oilseed meals could be included in the energy concentrates group on the basis of their energy content.
Depending on the activity of an animal, feedstuffs in this class may make up a substantial portion of an animal's total diet. As such, the energy feeds may make significant contributions of other nutrients such as amino acids, minerals, and vitamins.
Cereal grains are produced by plants in the grass family grown primarily for their seeds. The cereal grains are usually harvested and fed as the mature dry seed (approximately 15 percent moisture), but for some crops, cereal grains may be fed in a high-moisture (approximately 25 to 30 percent moisture) form that has been ensiled and fermented.
Grains are less variable in composition than forages, and it is usually acceptable to use reference values for nutrient content when formulating rations. However, soil fertility, weather, disease, and insect damage all may affect the development of seed, and under certain circumstances, its nutrient value may not be well represented by average values found in reference sources.
Because of the numerous ways of expressing energy content, and the fact that for at least some species feed energy value is determined based on feed passage rate, it is difficult to speak in generalities. In fact, historically, feed companies have kept secret the energy content of the finished feeds they sell for fear that a competitor might make improper energy comparisons between feeds to achieve a sales advantage.
The primary component responsible for the high-energy value of grains is carbohydrate. The nonfiber carbohydrate composition of most grains will range from 60 to 70 percent. The fiber carbohydrate in most grains will range from 2 to 12 percent, measured as crude fiber and 9 to 30 percent, measured as neutral detergent fiber. The fat content of most grains will vary from 1 to 6 percent, measured as ether extract. In contrast to energy content, the crude protein content of feed grains is relatively low, ranging from 8 to 12 percent. Calcium and phosphorus content of grains is low. Grains contain low to moderate levels of vitamins.
Hulls of grain are high in fiber and have a significant effect on feeding value. Most grains are processed (ground, rolled, etc.) to some extent before feeding to break the hull. This improves access for digestive enzymes to the grain's nutrients.
The United States government has established standards for assessing grain quality (USDA, 1987). The criteria for these grain standards are (1) test weights per bushel, (2) moisture content, (3) foreign material, (4) broken and damaged kernels, and (5) discoloration. Some grains have additional criteria. U.S. Grade 1 is the highest quality and U.S. Sample Grade is the lowest quality.
Corn grain (IFN 4-02-931) Proximate analysis, percent as fed basis * Crude protein: 8.9 * Crude fat: 3.8 * Crude fiber: 2.3
Major feed applications Corn, in areas where it grows well, will produce more digestible nutrients per unit of acreage than any other grain crop. It is very digestible and palatable for most domestic animals. Plant breeders have produced different varieties of corn to improve one or more characteristics in normal corn. High-lysine corn is a variety of corn bred to contain higher levels of the amino acids lysine, and tryptophan. Waxy corn is a variety that has a different type of starch than usual corn.
Corn grain can be preserved as high-moisture corn by ensiling. Optimal moisture levels at harvest are 25 to 30 percent. High-moisture corn should be processed before feeding for maximum feed efficiency.
Corn grain for use in livestock feed is usually ground, cracked, or rolled before being fed to animals. Many feed products are produced as coproducts of the milling of corn grain for use as food for people. The systems used for milling of corn grain fall into two categories: dry milling and wet milling (Figure 3-7).
Dry milling is used to process grain into a meal form and to extract the outer hull to produce corn flour. Corn flour is used in dry mixes such as for pancakes, doughnuts, batters, and snacks. When corn is dry milled, hominy feed may be produced as a coproduct. Hominy feed is higher than corn grain in protein, fat, and fiber, and it is lower than corn meal in nonfiber carbohydrate.
[FIGURE 3-7 OMITTED]
In wet milling, corn and other grains are processed into fractions concentrated in starch, protein, fiber, and oil. Coproducts resulting from the wet milling of corn include corn gluten meal and corn gluten feed, both of which are considered to be protein supplements rather than energy concentrates.
In the distilling industries, ethyl alcohol is produced by fermenting corn and other grains. The coproduct, distillers' grains, is generally considered to be a protein supplement rather than an energy concentrate. Distillers' grains is usually produced by starting with the whole grain, grinding it to a meal as in the dry milling process, and then proceeding with the fermentation. It is also possible to produce a distillers' grains coproduct by starting with the starch produced in wet milling. A similar feedstuff, brewers' grains, is a coproduct of the brewing industry, and is also considered to be a protein supplement.
Grain sorghum or milo (IFN 4-04-383) Proximate analysis, percent as fed basis * Crude protein: 10.5 * Crude fat: 2.8 * Crude fiber: 2.4
Major feed applications Sorghum is a hardy plant that is able to withstand heat and drought better than most grain crops. In addition, it is resistant to some insect pests that are problems for other grains and is adaptable to a wide variety of soil types. Consequently, sorghum is grown in many areas where corn does not do well. In areas where corn grows well, sorghum will yield less than corn. The seed from all varieties is small and relatively hard, and usually requires some processing for good animal utilization.
Sorghum grains have 90 to 95 percent of the feed value of corn. Bird-resistant varieties, whose seed coats are high in tannin, are not well liked by most domestic animals.
Wheat grain (IFN 4-05-211) Proximate analysis, percent as fed basis * Crude protein: 14.0 * Crude fat: 1.7 * Crude fiber: 2.5
Major feed applications In the United States, wheat is rarely grown for animal feed. All commonly grown varieties were developed with flour milling qualities in mind rather than feeding values. The hard winter wheats are high in protein, averaging 13 to 15 percent, but the soft wheats have less. The amino acid distribution is better than that of most cereal grains, and wheat is a very palatable and digestible feedstuff with a relative value equal to corn. Some processing (grinding or rolling) is required for optimum utilization.
Milling coproducts from the production of wheat flour account for about 25 percent of the kernel. They are classified on the basis of decreasing fiber as bran, middlings, shorts, red dog, and feed flour. The bran and middlings are from the outer layers of the seed and contain more protein than the grain, although they are deficient in lysine and methionine as well as some other essential amino acids. These outer layers of the seed are relatively good sources of most of the water-soluble vitamins except niacin. They are low in calcium and high in phosphorus and magnesium.
Wheat is the grain used to make most breads and bread products sold in the United States. Under certain circumstances, these products may be declared unfit for human consumption but are still wholesome. Such bakery waste may be used in livestock feed.
Barley grain (IFN 4-00-549) Proximate analysis, percent as fed basis * Crude protein: 11.6 * Crude fat: 2.0 * Crude fiber: 6.0
Major feed applications Although a small amount goes into human food and a substantial amount is used in the brewing industry, most of the barley produced in the United States is used for animal feeding.
Barley contains more total protein and higher levels of the essential amino acids lysine, methionine, and tryptophan than corn grain. Lightweight barley tends to be higher in fiber, less digestible, and lower in energy than heavy weight barley. Barley is a very palatable feedstuff, particularly when rolled before feeding.
Oat grain (IFN 4-03-309) Proximate analysis, percent as fed basis * Crude protein: 12.0 * Crude fat: 4.5 * Crude fiber: 12.0
Major feed applications As a source of energy for livestock, oats is relatively unimportant. Asubstantial amount of the oats produced goes into human food. The protein content of oats is relatively high and the amino acid distribution is more favorable than that of corn. The hull is fibrous and poorly digested, even when ground. Oats may be milled to separate the hulls from the inner portions of the grain, called the groats. Oat groats have a feeding value comparable to corn, but the price is too high to compete with corn. Oat groats are not widely used except in rations where cost is a minor factor, such as early weaning diets for pigs.
Coproducts from Sugar and Citrus Industries Molasses, cane (IFN 4-04-696) Proximate analysis, percent as fed basis * Crude protein: 3.0 * Crude fat: 0 * Crude fiber: 0
Major feed applications Molasses is a major coproduct of sugar production from sugar beets and sugar cane. Molasses may also be produced as a coproduct during the manufacture of dried citrus pulp. Wood molasses or hemicellulose extract is produced as a coproduct during the manufacture of some pressed wood products. Finally, starch molasses is a coproduct produced during the manufacture of dextrose from corn and sorghum.
The primary constituents of all molasses products are sugars. The sugar content of different molasses products will vary and an optical instrument called a brix refractometer is used to assess sugar content in molasses products. Worldwide, molasses is traded at a value of 79.5 brix.
Whereas the carbohydrate in most energy concentrates is in the form of starch, the carbohydrate in molasses is in the form of sugar. In ruminant nutrition, it is recognized that this type of carbohydrate plays a unique role in maximizing rumen productivity.
The sweet taste of molasses makes it palatable to most livestock species. In addition, molasses is of value in reducing dust, aiding pellet quality, serving as a vehicle for feeding medicants or other additives, and as a component of mixed liquid supplements. Because of its stickiness, molasses can create problems with mixing, processing, and handling equipment at the feed mill, and for this reason, the amount of molasses that can go into a mixed feed is limited.
Beet pulp (IFN 4-00-669) Proximate analysis, percent as fed basis * Crude protein: 9.0 * Crude fat: 0.5 * Crude fiber: 16.0
Major feed applications Dried beet pulp is the residue remaining after extraction of most of the sugar from sugar beets. Because of its high fiber content, dried beet pulp may be used as a forage alternative. It frequently has molasses added before drying, and may be sold in shredded or pelleted form. Because of the sugar content, the dried beet pulp is very palatable to most livestock.
Citrus pulp (IFN 4-01-237) Proximate analysis, percent as fed basis * Crude protein: 6.2 * Crude fat: 3.2 * Crude fiber: 13.0
Major feed applications Citrus pulp is the residue remaining after extraction of the juice from citrus fruit. Like beet pulp, citrus pulp is high in fiber content and so may be used as a forage alternative. Because of the residual sugar, citrus pulp is very palatable to most livestock.
Forage Substitutes Kelp meal Proximate analysis, percent as fed basis * Crude protein: 7.5 * Crude fat: 3 * Crude fiber: 7
Major feed applications Kelp meal is a feed supplement made from the Ascophyllum nodosum seaweed (algae) growing in the North Atlantic. As a feed supplement, kelp is rich in trace minerals and it is high in fiber. Kelp is most commonly fed as part of feed that is certified organic.
Soybean hulls (IFN 1-04-560) Proximate analysis, percent as fed basis * Crude protein: 11.0 * Crude fat: 1.9 * Crude fiber: 36.5
Major feed applications Soybean hulls contain a high level of digestible fiber and may be heat-treated to improve feeding value. Heat-treated soybean hulls are called soybean mill run, soybean flakes, or soybran flakes. Untreated soybean hulls contain the enzyme urease, and for this reason, should not be fed with urea because the urease will rapidly convert urea to ammonia. If this ammonia is absorbed, the animal may show symptoms of breathing difficulty, incoordination, tetany, and death.
Citrus pulp and beet pulp These feedstuffs have been discussed as coproducts from the sugar and citrus industries. Because of their high fiber content, they may be used as forage substitutes.
Fats and Oils Proximate analysis, percent as fed basis * Crude protein: 0 * Crude fat: 82.5 to 100 * Crude fiber: 0
Major feed applications Fats fed to livestock are primarily animal fats derived from rendered beef, swine, sheep, or poultry tissues. Animal/vegetable blends are also used, but pure vegetable oils are rarely used due to their high cost.
Although most animals need a source of the essential fatty acids, these are present in most feedstuffs and supplementation is not usually required. Fats are added to rations for several reasons. As a source of energy, fats are highly digestible and supply at least 2.25 times as much energy per pound as starch, sugar, or protein. Because of their high energy value, fats can be used to increase energy density of a ration. Fats may also improve rations by reducing dustiness and increasing palatability. Feeds containing added fat usually have antioxidants added to help protect against rancidity.
High levels of fats are used in milk replacers for young ruminants. Mature ruminants, however, are less tolerant of high fat levels than are monogastrics. Concentrations in mature ruminant rations of more than 6 percent may cause reduced fiber digestibility (Palmquist & Jenkins, 1980). Rations formulated for carnivores such as cats, trout, and dogs will contain much higher fat levels than those for ruminants. Nonruminant herbivores such as horses and rabbits can tolerate large amounts of dietary fat but high fat rations are seldom beneficial for these animals. High levels of unsaturated fat in swine diets may affect pork quality for reasons explained in Chapter 8.
Images and supplemental information on protein supplements are found in the file titled Images.ppt on the text's accompanying On-Line Companion. To view this file please go to http://www.agriculture.delmar.com/ and click on Resources. Click on On-Line Resources and select from the titles listed.
The term quality, as it relates to protein supplements, refers to the feedstuff's amino acid content. The protein supplement is considered to be of good quality if its amino acid content resembles the amino acid requirements of the animal. Most protein supplements of animal origin are of better quality than protein supplements of plant origin. An exception is feather meal. The protein in feather meal is of only fair quality because the amino acid profile of feather meal is only a fair match to that needed by most livestock. Protein supplements are usually more expensive than energy concentrates, so optimal use is a must in any practical feeding system.
Plant Protein Sources
The most important sources of plant protein are soybeans, canola (a variety of rapeseed), and cottonseed, with lesser amounts from peanuts, flax (linseed), sunflower, sesame, and safflower. These seeds contain about 21 percent oil (dry matter basis), which is usually extracted and used for human food products. High-protein meals from these oilseeds are coproducts of the oil extraction process. When economical, the whole oilseeds themselves can be used in livestock diets. These are usually heat-treated to improve feed value. Although not as high in protein content, distillery and brewery coproducts are often economical sources of protein and other nutrients for livestock, particularly herbivores whose digestive tracts are capable of utilizing fibrous material.
Oil-bearing seeds are usually processed to extract the oil for human food. Two primary processes are used for removing the oil from these oilseed crops. This extraction is done using either the expeller method, a mechanical process, or the solvent method, a chemical process. From a feed value standpoint, the primary difference in these types is that the solvent extraction process is more efficient in removing the oil. As a result, the oilseed meal produced using solvent extraction is a bit lower in fat and energy than the oilseed meal produced using the expeller or mechanical process of oil extraction.
Protein-rich coproducts from the oil extraction process are of great value in livestock feed. These oilseed meals are high in crude protein, most being over 40 percent, as fed basis. With the exception of soybean meal, the protein in oilseed meals is of only fair quality. The essential amino acids lysine and methionine are usually the acids of most concern. Soybean meal is rich in lysine, and its protein is therefore considered to be of good quality. Calcium content in oilseed meals is usually low, but most test high in phosphorus. Usually, at least half of the phosphorus in oilseed meals is in the form of phytate, a form poorly utilized by monogastrics. Oilseed meals generally contain low to moderate levels of the vitamins.
Soybean meal 49 percent (IFN 5-04-612) Proximate analysis, percent as fed basis * Crude protein: 49.0 * Crude fat: 1.0 * Crude fiber: 3.0
Major feed applications In processing soybeans, the oil-extracted meal is toasted, a process that improves the value of its protein. Its protein is generally standardized at either 44 percent or 49 percent crude protein, as fed basis, depending on the amount of hull contained in the meal.
The milling of soybeans results in several coproducts that are used in livestock feeds. The value of soybean hulls as a forage substitute has been discussed. Lecithin and soapstock are produced during the refining of soybean oil. Both are liquids and both are high in energy.
When economical, whole soybeans, or "full fat" soybeans are an excellent feedstuff for ruminants. To improve feeding value, the beans are usually heattreated, usually through roasting. The heat destroys the bean's toxins, and for ruminants, alters the protein to increase the proportion that is resistant to microbial degradation in the rumen. Excessive heat treatment, however, can render the protein totally indigestible. It appears that optimum heat treatment of soybeans intended as a protein supplement for lactating cows is heating the soybeans to a temperature of 295[degrees] F and holding them there for 30 minutes (Satter, 1994). By following these guidelines, 50 to 60 percent of the protein in roasted soybeans will be resistant to microbial degradation in the rumen.
Cottonseed meal (IFN 5-07-873) Proximate analysis, percent as fed basis * Crude protein: 41.5 * Crude fat: 1.5 * Crude fiber: 12.5
Major feed applications The protein of cottonseed meal is of only fair quality. Most meals are standardized at 41 percent crude protein, as fed basis. Cottonseed meal contains a yellow pigment, gossypol, which is relatively toxic to monogastric species, particularly young pigs and chicks. In addition, the gossypol in cottonseed meal results in poor egg quality. The gossypol is made in glands of the plant. These glands may be removed in processing. Also, "glandless" varieties of cotton have been developed that have very low levels of gossypol. Unfortunately, without the gossypol, high levels of insecticides must be used on these crops to achieve acceptable yields.
Cottonseed hulls are sometimes used as a forage for ruminants.
Whole cottonseed is a widely used feed for ruminants. It contains high levels of protein, fat, and fiber. Generally, whole cottonseed is fed to mature dairy cows at no higher than 6 lb. per head per day.
Other oilseed meals Other oilseeds are processed to extract the oil for use in human food, producing a high-protein coproduct that is used in livestock feed. Examples include canola meal, linseed meal, peanut meal, sunflower meal, and safflower meal.
Canola meal is made from a variety of rapeseed that has less hull and higher digestibility. Most of the toxic qualities of the earlier varieties of rapeseed have been removed in canola, but to avoid off-flavored eggs, canola meal should not be fed to brown-egg layers (NRC, 1994). Canola meal that is not properly heat processed may be goitrogenic for poultry.
Linseed meal is made from flax seed. It accounts for only a small part of the total plant protein produced in the United States. As a consequence of its reputation for enhancing hair coat appearance ("bloom"), it is widely fed to show cattle. Linseed meal is toxic to poultry (Nakaue & Arscott, 1991).
Farmers and ranchers with peanut allergies should avoid use of peanut meal in the feed to which they are exposed.
Safflower is a plant grown in limited amounts for its oil. The meal is high in fiber and low in protein unless the hulls are removed.
Sunflowers are produced for oil and seeds.
Distillers' dried grains (IFN 5-28-236) Proximate analysis, percent as fed basis * Crude protein: 27.0 * Crude fat: 8.0 * Crude fiber: 9.1
Major feed applications Coproducts of the distilling industries are valuable animal feedstuffs. These industries produce ethyl alcohol for fuel or in the manufacture of whiskey. The main distillery coproducts are dried distillers' grains and dried distillers' solubles, or mixtures thereof.
Brewers' dried grains (IFN 5-02-141) Proximate analysis, percent as fed basis * Crude protein: 25.6 * Crude fat: 6.5 * Crude fiber: 16.0
Major feed applications Coproducts of the beer-brewing industries are also used in animal feeds. The main brewers' coproducts are wet and dried brewers' grains. The wet brewers' coproduct will spoil quickly, and must be consumed within a week in cold weather and within a couple of days in warm weather. It is possible to preserve wet brewers' grains by ensiling.
Corn gluten meal (IFN 5-28-242) Proximate analysis, percent as fed basis * Crude protein: 60.0 * Crude fat: 2.5 * Crude fiber: 2.0
Major feed applications Corn gluten meal is the residue after removal of the kernel's starch, germ, and bran. It contains approximately 60 percent protein, the highest of any plant protein product. As with all products derived from corn grain, the protein of corn gluten meal is of only fair quality.
Corn gluten feed (IFN 5-28-243) Proximate analysis, percent as fed basis * Crude protein: 22.0 * Crude fat: 3.0 * Crude fiber: 8.0
Major feed applications Corn gluten feed is the residue after removal of the starch and gluten. Because corn gluten feed contains the bran portion of the corn grain, its protein content is much less than that of corn gluten meal.
Animal protein sources
The combination of feedstuffs in the balanced ration must result in the delivery of the type and quantity of amino acids required by the animal. For monogastrics, the amino acids must come directly from the combination of protein sources contained in the ration. Animal protein sources are useful because they are generally of higher quality than plant protein sources. However, palatability problems often limit the amount of animal protein products that may be included in livestock diets. The inclusion of mammalian and poultry derived proteins in livestock diets may be a factor in the transmission of disease. This practice is currently under review by the USDA and FDA.
Blood meal (IFN 5-00-380) Proximate analysis, percent as fed basis * Crude protein: 80.0 * Crude fat: 1.2 * Crude fiber: 1.0
Major feed applications Blood meal is a coproduct of the animal rendering industry. When dried without excessive heat as in the spray- or ring-drying process, blood meal is a high protein content, high protein quality feedstuff. If excessive heat is used in processing blood meal, however, the protein is damaged and the feedstuff's value is reduced. Most of the protein in blood meal is resistant to microbial degradation in the rumen.
Feather meal, hydrolyzed (IFN 5-03-795) Proximate analysis, percent as fed basis * Crude protein: 85.0 * Crude fat: 3.0 * Crude fiber: 2.0
Major feed applications There are four important issues regarding feather meal as a feedstuff.
1. Feathers test high in crude protein, but the protein in feathers is in the form of keratin, which animals cannot digest. As a feedstuff, therefore, feather meal must be hydrolyzed. Hydrolysis breaks the internal bonds of the keratin in feathers so that animal enzymes can effectively digest the protein.
2. The protein of feather meal is of only fair quality; its amino acid profile is not a good match for growing and producing livestock.
3. Feather meal is probably the least palatable of the animal protein supplements for most livestock. Its use in the ration must be minimal to avoid affecting overall ration palatability. In the dairy industry, feather meal is best kept to less than 1 lb. per animal per day. In swine and poultry diets, it should not be fed at more than 5 percent of the ration (Chiba, Ivey, Cummins, & Gamble, 1996).
4. Feather meal is inexpensive. For this reason, there is considerable incentive to try to overcome its deficiencies and use it more in animal diets.
Fish meal, Herring (IFN 5-02-000) Proximate analysis, percent as fed basis * Crude protein: 72.0 * Crude fat: 8.4 * Crude fiber: 0.6
Major feed applications The most common fish used to produce fish meal are menhaden, herring, anchovy, whitefish, and redfish. The definition of fish meal is such that it allows for significant variation among sources. Fish meal may be made from whole fish or fish cuttings (also described as seafood processing waste). If the origin of fish meal is fish cuttings, it may be the portion of the fish remaining after the filets have been removed. This product will test high in mineral content. Mineral content is reported as "ash" on a laboratory analysis. Fish meal with 25 percent ash or more is of low value as a feedstuff for fish. Fish meal also may or may not be produced from fish products from which the oil has been extracted.
Meat meal (IFN 5-00-385) Proximate analysis, percent as fed basis * Crude protein: 54.8 * Crude fat: 9.7 * Crude fiber: 2.8
Major feed applications Meat meal is a rendered product derived from the tissues of slaughtered mammals.
Meat and bone meal (IFN 5-00-388) Proximate analysis, percent as fed basis * Crude protein: 50.0 * Crude fat: 9.5 * Crude fiber: 2.5
Major feed applications Meat and bone meal is the rendered product from mammal tissues including bone. Because of the inclusion of bone, there is a possibility of contamination with nervous tissue (the spinal cord running inside the backbone). Nervous tissue is the source of the agent that causes bovine spongiform encephalopathy (BSE) ("mad cow disease") and therefore meat and bone meal may not be fed to ruminant animals.
Nonprotein Nitrogen Urea Proximate analysis, percent as fed basis * Crude protein: 287.0 * Crude fat: 0 * Crude fiber: 0
Major feed applications Although some feedstuffs, particularly hay crop silage, contain substantial amounts of nonprotein nitrogen (NPN), from a practical point of view, NPN in formula feeds usually refers to urea. Rations containing large amounts of hay crop silage will not benefit from the addition of urea.
NPN, especially urea, is primarily used for feeding animals with a functioning rumen. The reason for this is that urea is a source of nitrogen that is converted by rumen microbes to ammonia, which is used by rumen microbes to build amino acids and protein. The microbes' protein is, in turn, used by the animal hosting the microbes when the microbes are ultimately washed out of the rumen and digested. Urea should be introduced to the diet gradually so that rumen microbes have an opportunity to adapt to its presence.
The companion application to this text predicts the amount of microbial protein produced in the rumen for dairy, beef, sheep, and goat rations. Levels of urea beyond that which results in increased microbial protein production are to be avoided as they can result in absorption of urea into the blood of the ruminant, leading to reproductive and health problems. Urea toxicity in livestock is evidenced by an ammonia odor on the animal's breath. Additional information regarding the feeding of urea and blood urea levels is found in Chapter 16.
Urea should not be fed with raw soybeans or raw soybean hulls. These feeds have urease activity that will result in the conversion of urea to ammonia, possibly leading to toxicity.
The main advantage of using urea in ruminant diets is a saving of feed dollars. In other words, amino acids can be manufactured from urea by rumen bacteria for less money than would be required to purchase intact protein.
Feed grade biuret is another source of nonprotein nitrogen. It was developed as an alternative to urea in an attempt to improve palatability and rumen-release characteristics.
Images and supplemental information on mineral supplements are found in the file titled Images.ppt on the text's accompanying On-Line Companion. To view this file please go to http://www.agriculture.delmar.com and click on Resources. Click on On-Line Resources and select from the titles listed.
Virtually all feedstuffs have some mineral content, but supplemental mineral is usually necessary in livestock rations to meet requirements. Which minerals must be supplemented and to what level can only be determined by analyzing the mineral content of the individual feedstuffs and calculating the contribution of each mineral from each feedstuff consumed in the ration.
Laboratory analysis is the only way to accurately determine the mineral content of a feedstuff. However, it is important to realize that the digestive tract of livestock may not be able to extract and absorb all the mineral that the analysis indicates is in the feedstuff. Bioavailability refers to the portion of the total mineral in the feedstuff that is absorbed into the blood from the digestive tube. The most important factors affecting mineral bioavailability are the mineral source, the method and amount of processing of the mineral source, and the livestock species fed. Ideally, the mineral content of each mineral source is accompanied by the bioavailability data for the animal to be fed, but this is not usually the case.
When bioavailable mineral values are not known, the requirement values are usually adjusted upward with so-called "safety factors" to account for the unavailable mineral content of feedstuffs. Mineral excretion due to the use of safety factors has become a pollution concern.
Mineral supplementation is best achieved by mixing the sources of mineral with the rest of the ration because many mineral sources are unpalatable. This is sometimes called "force feeding" minerals. Animals do, however, have an appetite for salt and will generally eat salt to meet their requirement. Salt may be offered to livestock in loose form or in block form.
Animals that have been fed diets deficient in salt may consume excess salt when a salt source is introduced. Such animals should be offered only as much salt as they require until their appetite for salt has returned to normal.
A salt source may be fortified with other minerals so that when the animal meets its salt requirement, it has also met its requirement for these other minerals. Such a trace mineralized salt source may also be offered in loose form or in block form. An example of the formula and analysis of one type of trace mineralized salt block is shown in Table 3-9.
Images and supplemental information on vitamin supplements are found in the file entitled Images.ppt on the text's accompanying On-Line Companion.
To view this file please go to http://www.agriculture.delmar.com/ and click on Resources. Click on On-Line Resources and select from the titles listed.
Vitamin content of feedstuffs varies based on the type of feedstuff, treatment during harvest, processing method if any, and the conditions and duration of storage of the feedstuff. Given the variation, it would seem logical that analysis of feedstuff vitamin content would be routine. However, this is not the case.
Determining the vitamin content of feedstuffs is time-consuming and expensive. It involves the use of biological and/or chemical methods of evaluation.
The biological method measures a feedstuff's potency in eliminating signs of a vitamin deficiency, and will include all sources of vitamin activity rather than a single vitamin source. The feed to be tested is fed at several levels to different groups of animals, typically rats or chicks, as a supplement to a vitamin-free diet that has caused symptoms of vitamin deficiency. The response to the feed is compared to a similar group of rats or chicks receiving a standard source f the vitamin at the level required.
A chemical method involves the use of chromatographic procedures to separate the biologically active vitamin source(s).
Analyzing the content of individual vitamins in feedstuffs is usually unnecessary. It is more cost effective to supplement vitamins to their required level than it would be to test feeds and supplement to meet calculated deficiencies. As indicated in Table 10-1, not all species require dietary supplementation of all vitamins.
Liquid feedstuffs include distillers' solubles, fish solubles, corn fermentation solubles, lecithin, soapstock, glutamic acid fermentation liquor, and propylene glycol. The most common liquid feedstuff is molasses, which is often used as a medium to carry other ingredients in liquid form. Technologies have been developed to incorporate many types of feed ingredients in liquid supplements. Intake of molasses-based liquid supplements in ruminant rations is usually limited to 1 to 3 lb. per head per day.
Images and supplemental information on additives are found in the file entitled Images.ppt on the text's accompanying On-Line Companion. To view this file please go to http://www.agriculture.delmar.com/ and click on Resources. Click on On-Line Resources and select from the titles listed.
In the feed industry, the term additive is used to identify ingredients in a ration that do not directly meet known nutrient requirements. Additives are usually used in small quantities and, therefore, require careful handling and mixing. The use of some additives is regulated by federal law (USDA, Center for Animal Health Monitoring). Any substance that has been implicated as a carcinogen when fed to any animal at any level may not be used as a feed additive. This is the result of the "zero tolerance" policy adopted by Congress as a result of the Delaney Clause passed by Congress in 1958.
Buffers are included in ruminant rations to help counteract the acid generated by ruminal fermentation of grain. Examples of buffers fed to livestock include sodium bicarbonate and sodium sesquicarbonate. Sodium bicarbonate is osmotically active and may influence performance in ruminant animals by increasing liquid turnover rate and thereby dry matter intake. Though technically an alkalizing agent and not a buffer, magnesium oxide is often used in livestock rations to prevent the accumulation of acid in the digestive system.
Polyunsaturated fats may react with oxygen and fall apart, leading to the creation of new compounds that are unpalatable and may be toxic. This process is called oxidative rancidity. Vitamins A, D, and E as well as several of the B vitamins may also be destroyed as a result of oxidative rancidity. To protect polyunsaturated fats from oxidative rancidity, antioxidants are often added (at approximately 0.25 lb./ton) to feeds. Examples include butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), and ethoxyquin. Several vitamins themselves act as antioxidants. However, as vitamins work to protect against oxidative rancidity in the feed, they are "used up" and are no longer available to the animal consuming the feed.
Hormones are made inside cells and are secreted by ductless glands into the blood, where they are carried to all parts of the body to exert their influence on tissues or other glands. Because fat-based compounds are absorbed by the digestive tract largely unaltered, feeding a fat-based hormone may result in absorption of that hormone. Feeding a protein-based hormone, however, will not result in absorption because proteins are digested and absorbed as amino acids. As a group, the fat-based hormones are called steroids. Synthetic steroids and substances that have steroid-like effects may be used as feed additives to improve feed efficiency and rate of gain. Steroids in feed may be used as a management tool to manipulate the estrous cycle so that animals all come into heat at the same time.
Antibiotics and Chemotherapeutic Agents
Most antibiotics are compounds produced by fungi, bacteria, or algae. Chemotherapeutic agents such as arsenical compounds are fed to swine and poultry for much the same reason as antibiotics.
Antibiotics and chemotherapeutic agents inhibit or destroy microorganisms in the animal that are detrimental to health or performance. In the feed industry, these substances are added at subtherapeutic levels (too low to be effective in treating disease) to reduce the incidence of subclinical bacterial infections, and to improve rate of gain and feed efficiency for approved species. Antibiotics are used in complete feeds at an inclusion rate of 2 to 10 mg/kg (parts per million); chemotherapeutic agents are usually used at somewhat higher inclusion rates. Antibiotics and chemotherapeutic agents fed at subtherapeutic levels are also helpful in controlling certain health problems such as respiratory infection, liver abscesses, foot rot, and diarrhea in livestock. These additives give the greatest response in those animals that are kept in unsanitary, stressful environments. The conditions under which these drugs may be used as feed additives are closely prescribed and care must be taken that they are used properly to avoid residues in human food. Antibiotic use as a feed additive is under review because of the risk that microorganisms that cause disease in humans may develop resistance through exposure to antibiotics in livestock feed. Regulations pertaining to the use of antibiotics and chemotherapeutic agents in the United States are found in the Feed Additive Compendium, which is published annually.
Ionophores are a unique type of antibiotic obtained from Streptomyces microorganisms. They are not used in treating human disease. Ionophores are fed to prevent coccidiosis in poultry and young ruminants, and to improve feed efficiency in growing and lactating ruminants.
Ionophores improve feed efficiency in ruminants by changing the microbial population in the rumen. Ionophores cause sensitive bacteria to lose potassium (a source of base) and the cell cytoplasm is, therefore, at risk of turning acid. These bacteria then use all available adenosine 5'-triphosphate (ATP) to pump acid out of the cell. With such a demand on the ATP supply, the sensitive bacteria stop growing.
Only Gram-positive bacteria are sensitive to ionophores. Gram-negative bacteria have outer membranes that keep ionophore out. In the presence of ionophore, the rumen population of Gram-negative bacteria grows along with the products they produce, and the population of Gram-positive bacteria declines along with the products they produce. The result is:
* Lower acetate-to-propionate ratio, because Gram-negative bacteria produce more propionate and Gram-positive bacteria produce more acetate.
* Decreased methane production because methane production is associated with the production of acetate (Gram-positive bacteria).
* Amino acid sparing (more efficient use of dietary protein) because some of the sensitive bacteria are guilty of converting amino acids to ammonia.
* Increased feed efficiency due to all of the above. Increased feed efficiency means that:
** less ingested feed will be needed to meet maintenance energy needs. Therefore, a greater portion of the energy in ingested feed will be available for other functions such as growth and lactation. The companion application to this text for beef and dairy heifers applies a credit to the feed NEm value, increasing the ration NEm concentration by 12 percent when ionophore is used. In the companion application, ionophore use in dry and lactating dairy cows results in a 12 percent reduction of the net energy required for maintenance, excluding that due to stress.
** maintenance energy needs will be more easily met with what little feed is ingested. By making it easier for the appetite-depressed cow at the start of her lactation to meet her maintenance energy needs, she will be less susceptible to all of the metabolic problems associated with an energy deficit.
* Most studies indicate that use of an ionophore results in a reduction in dry matter intake that diminishes at least some of the benefits listed above. The companion application to this text for beef animals predicts a reduction of 6 percent dry matter intake when ionophore is used. In the dairy application, the reduction in dry matter intake due to ionophore use is an inputted value from within the range of 0 to 6 percent.
Direct-Fed Microbials or Probiotics
As the name implies, probiotics are products that promote the growth of microbial populations. Probiotics, or direct-fed microbials, consist of microbes that have been selected for specific desirable characteristics. These products may be helpful in establishing a more desirable population of gastrointestinal microorganisms. The use of probiotics in livestock diets has been reviewed (Ghorbani, Morgavi, Beauchemin, & Leedle, 2002).
Nutrients as Additives
Nutrient requirements are established based on the level of nutrient needed to support health and performance in animals under usual circumstances. Animals in unusual circumstances, such as those experiencing disease or severe strain, may benefit from higher levels of some nutrients. Nutrients used to help the animal deal with unusual circumstances are appropriately described as additives. Another term that has been used to describe nutrients used in this way is nutriceuticals.
In the ruminant animal, feedstuffs are subject to microbial activity before reaching the site of absorption. This means that amino acids and most watersoluble vitamins that are in the ration will not be available to the ruminant animal. For this reason, various technologies have been developed to protect substances from the microbes while allowing them to be absorbed by the ruminant. This has allowed researchers to deliver nutrients directly to the animal. Feeding a rumen-protected source of the B vitamin choline improves liver performance (Piepenbrink & Overton, 2003), and may help to prevent fatty liver and ketosis in high producing cows.
Feeding niacin as a nutriceutical has reduced plasma ketone concentration (Grummer, 1993) and may help prevent ketosis in dairy animals when fed at levels well beyond the usual requirement.
Health and performance benefits have been shown when feeding unusually high levels of chromium (Lindemann et al., 1995), copper (Davis et al., 2002), and zinc (Hill et al., 2000) to swine.
Flavoring agents are feed additives that are popular in the pet food industries. Studies show that animals given a choice will often show a preference for feed containing flavor additives. However, this preference generally does not translate to increased consumption of flavored feed over unflavored feed when no choice is offered.
A common flavor enhancer is termed digest. Digest is sometimes sprayed onto dry pet foods. Digest is made from poultry and beef byproducts using an enzymatic process to reduce these materials to a liquid.
Yeast and Yeast Culture
Yeast culture is used in microbiology to stimulate the growth of specific types of bacteria, particularly those that utilize lactic acid. As a feed additive, yeast culture is used to increase the vitality of bacteria inhabiting the digestive tract. It is often included in the diet to help animals weather stressful environments or conditions. Live yeast is a feed additive intended to deliver the yeast culture through the activity of the live yeast in the animal's digestive tract.
Animals produce enzymes in the glands of their digestive system. In addition, enzymes are produced by the microbes inhabiting animal digestive systems, and feedstuffs may contain active enzymes when eaten. Needless to say, enzymes play an important role in digestion. For this reason, there has been much research to determine if digestion would be improved by the dietary supplementation of enzymes.
To date, the only enzyme that has gained acceptance in the feed industry is phytase. Phytase is an enzyme that degrades phytin or phytic acid. Phytin is the compound containing most of the phosphorus in grains. By using phytase, producers can meet animal phosphorus requirements with less total dietary phosphorus, this leads to reduced phosphorus excretion. Because phytase is made by the microbes inhabiting the rumen, phytase is only considered for monogastric animals, particularly poultry (Perney, Cantor, Straw, & Herkelman, 1993) and swine (O'Quinn, Knabe, & Gregg, 1997).
Xanthophylls are carotenoid pigments that are used to contribute to the coloration of livestock tissues. Astaxanthin is a xanthophyll used in salmon and trout diets to achieve an attractive flesh and/or skin pigmentation. Corn gluten meal is a source of xanthophylls that is used in poultry diets to deepen the color of egg yolk and to impart a yellow tint to the skin of broilers. Other sources of xanthophylls include marigold petal meal, dried algae, and alfalfa meal. Xanthophylls may also act as antioxidants, and as such, may have positive effects on health and reproductive performance.
Mold Inhibitors and Mycotoxin Binders
The most effective ways to keep feed from becoming moldy are to keep feed moisture content below 13.5 percent, keep feed fresh, and keep equipment clean. Mold inhibitors can be temporarily effective in stopping mold growth after it has begun or in protecting feed from the start of mold growth. Examples of mold inhibitors include organic acids (propionic, sorbic, benzoic, and acetic acids) and salts of organic acids (calcium propionate and potassium sorbate). Although it is sometimes used as a mold inhibitor, the effectiveness of copper sulfate is difficult to document.
One of the problems caused by mold growth in feed is the production of toxins called mycotoxins. Mycotoxin binders are products that bind mycotoxins and may thereby reduce their toxic effects on livestock consuming the unwholesome feed. Mycotoxin binders are clay compounds, an example of which is sodium bentonite. For a discussion of the problems associated with moldy feed, see Chapter 13.
There are many other types of substances that find their way into livestock diets to serve a variety of functions, including wormers (anthelmintic agents), fly control agents, pellet binders, bloat preventatives, and ergogenic aids. The latter are feed products designed to improve the athletic performance of horses. Products such as sodium bicarbonate, carnosine, and carnitine are sometimes fed as ergogenic aids. The feeder should be skeptical of these and other products described as ergogenic aids because in most cases, they provide no benefit and may be banned by racing authorities.
Finished feeds are mixes or blends of ingredients that are handled as a single feedstuff. It is easiest to define and describe finished feeds by considering the products manufactured and sold by feed mills. Feed mills sell the following types of finished feeds.
1. Complete feeds
2. Concentrate feeds
3. Base mixes
A complete feed is all necessary ration components that are inventoried by the feed mill. Since feed mills generally do not inventory forages, the complete feed contains all nonforage ration components. For nonforage eaters, the complete feed makes up the entire daily ration. It may be fed as meal, pellets, crumbles, or in the form of a liquid or paste. Complete feed may also be available in a form described as textured or coarse. A textured complete feed generally contains up to 15 percent molasses and other ingredients in a variety of forms including pellets, whole grains, and processed grains. Because of the molasses content, textured feeds may also be described as sweet feeds. For ruminant animals and any animal that is to be fed forage, a complete feed contains all ration components except the forage.
Regardless of the type of farm or ranch, livestock are always fed complete feeds. The complete feed may be fed through a total mixed ration (TMR) in which a mixer has been used to blend all ration components, including forage. Alternatively, the complete feed may be fed through a component feeding system in which at least some individual ingredients are fed unmixed. In either system, by the end of a 24-hour period, livestock have received a complete feed, and if the animal is a herbivore, forage.
Complete feeds may be purchased directly from the feed mill. However, savings may be realized by purchasing some feedstuffs that would be part of the complete feed from different sources. These purchase savings must be weighed against the additional storage, handling, and mixing expenses that would be incurred in this type of feed buying strategy.
Corn meal is the major component in most complete feeds. Often, a farm or ranch will purchase a blend of all ingredients of the complete feed except the corn meal from one source and purchase the corn meal separately. Ablend of all ingredients except the corn meal is called a concentrate or supplement. The concentrate inclusion rate in a ton of complete feed is usually at least 200 lb.
Soybean meal is the second most plentiful component of most complete feeds. If the farm or ranch purchases corn meal and soybean meal separately, the remaining ingredients are purchased as a base mix or super concentrate. A base mix may still contain some of the protein source for the complete feed, but it contains all the mineral fortification, both macro and trace, and the vitamins. The base mix inclusion rate in a ton of complete feed is usually 100 to 200 lb.
The macro minerals as a group are the third most plentiful component of most complete feeds. If the farm or ranch purchases corn meal, soybean meal, and macromineral sources such as salt, limestone, dicalcium phosphate, and magnesium oxide separately, what remains to make the complete feed is one or more premixes. One premix may contain all the remaining ingredients--the trace minerals, vitamins, mold inhibitors, flavor ingredients, antibiotics, and so on. Alternatively, these ingredients may be packaged in separate premixes. The premix inclusion rate in a ton of complete feed is usually 5 to 100 lb. The smaller inclusion rate premixes will usually include a carrier to ensure that the mixing equipment used will be able to effectively mix the target ingredient. Examples of carriers include rice hulls, calcium carbonate, ground corn cobs, and wheat middlings.
Chapter 3 lists and describes the general categories of feedstuffs. The categories, as identified by the NRC's IFN are:
1. Dry forages
2. Pasture, range plants, and feeds cut, and fed green
3. Silages 4. Energy concentrates
5. Protein supplements
Some of the nutritional and agronomic characteristics of the eight feed categories are discussed. Because forages are an important part of the diet for some livestock types, and because the forages are usually homegrown, special emphasis is given to the harvesting and storage of forages. The application of feedstuffs from the various categories in developing a balanced ration for livestock is described.
1. Give three examples each of grasses and legumes. Comparing grasses and legumes of similar maturity, which two nutrients are generally present at a higher concentration in legumes?
2. Why are spoilage bacteria and molds unable to grow in well-made hay?
3. Compare and contrast losses that occur when making dry hay versus hay crop silage.
4. Discuss the importance of reducing the moisture content of the hay crop prior to ensiling.
5. What factors influence the amount of packing that is necessary to effectively exclude oxygen in a hay crop put up in a horizontal silo?
6. High stocking density and short access time are characteristic of what type of pasture management?
7. Describe the following terms as they refer to mixed feeds: complete feed, concentrate, base mix, and premix.
8. What is the approximate oil content in the whole oilseeds? Among the oilseed meals, which is the source of the highest quality protein?
9. When discussing feed protein sources, to what does the term protein quality refer?
10. What does the following formula calculate?
[(wet weight - dry weight)/wet weight] x 100
What is the recommended percent dry matter range for corn silage? What is the recommended percent dry matter range for hay crop silage?
Abaye, A. O., Allen, V. G., & Fontenot, J. P. (1997). Grazing sheep and cattle together or separately: Effect on soils and plants. Agronomy Journal. 89, 380-386.
American Sheep Industry Association, Inc. (1996). Sheep production handbook (pp. 384-385). Denver, CO: C&M Press.
Cheeke, P. R. (1995). Endogenous toxins and mycotoxins in forage grasses and their effects on livestock. Journal of Animal Science. 73, 909-918.
Cherney, D. J. R. (1991, October 10). Low-lignin, brown mid-rib genotypes and their potential for improving animal performance (pp. 13-19). Proceedings Cornell Nutrition Conference for Feed Manufacturers, Rochester, NY.
Chiba, L. I., Ivey, H. W., Cummins, K. A., & Gamble, B. E. (1996). Hydrolyzed feather meal as a source of amino acids for finisher pigs. Animal Feed Science and Technology. 57, 15-24.
Colenbrander, V. F., Bauman, L. F., & Lechtenberg, V. L. (1975). Feeding value of low lignin corn silage. Journal of Animal Science. 41, 332.
Davis, M. E., Maxwell, C. V., Brown, D. C., de Rodas, B. Z., Johnson, Z. B., Kegley, E. B., Hellwig, D. H., & Dvorak, R. A. (2002). Effect of dietary mannan oligosaccharides and (or) pharmacological additions of copper sulfate on growth performance and immunocompetence of weanling and growing/finishing pigs. Journal of Animal Science. 80, 2887-2894.
Feed Additive Compendium. (2004). Minnetonka, MN: Miller Publishing Co.
Fox, D. G., Tylutki, T. P., Van Amburgh, M. E., Chase, L. E., Pell, A. N., Overton, T. R., Tedeschi, L. O., Rasmussen, C. N., & Durbal, V. M. (2000). The net carbohydrate and protein system for evaluating herd nutrition and nutrient excretion (CNCPS vol. 4.0. p. 212). Animal Science Department Mimeo 213, Cornell University, Ithaca, NY.
Frenchick, G. E., Johnson, D. G., Murphy, J. M., & Otterby, D. E. (1976). Brown midrib corn silage in dairy cattle rations. Journal of Dairy Science. 59, 2126.
Ghorbani, G. R., Morgavi, D. P., Beauchemin, K. A., & Leedle, J. A. Z. (2002). Effects of bacterial direct-fed microbials on ruminal fermentation, blood variables, and the microbial populations of feedlot cattle. Journal of Animal Science. 80, 1977-1985.
Grummer, R. R. (1993). Etiology of lipid-related metabolic disorders in periparturient dairy cows. Journal of Dairy Science. 76, 3882-3896.
Hill, G. M., Cromwell, G. L., Crenshaw, T. D., Dove, C. R., Ewan, R. C., Knabe, D. A., Lewis, A. J., Libal, G. W., Mahan, D. C., Shurson, G. C., Southern, L. L., & Veum, T. L. (2000). Growth promotion effects and plasma changes from feeding high dietary concentrations of zinc and copper to weanling pigs (regional study). Journal of Animal Science. 78(4), 1010-1016.
Hoglund, C. R., (1964). Michigan State University. Agricultural Economics Publication # 947.
Holland, C., & Kezar, W. (1995). Pioneer forage manual--A nutritional guide. Des Moines, IA: Pioneer Hi-Bred International, Inc.
Lindemann, M. D., Wood, C. M., Harper, A. F., Kornegay, E. T., & Anderson, R. A. (1995). Dietary chromium picolinate additions improve gain:feed and carcass characteristics in growing-finishing pigs and increase litter size in reproducing sows. Journal of Animal Science. 73,(2) 457-465.
Nakaue, H. S., & Arscott, G. H. (1991). Feeding poultry. In D. C. Church (Editor), Livestock feeds & feeding (3rd edition). Englewood Cliffs, NJ: Prentice-Hall.
National Research Council. (1972). Atlas of nutritional data on United States and Canadian feeds. Washington, DC: National Academy Press.
National Research Council. (1994). Nutrient requirements of poultry (9th revised edition). Washington, DC: National Academy Press.
Nolan, T., & Connolly, J. (1989). Mixed vs. monograzing by steers and sheep. Animal Production 48, 519-533.
Northeast DHIA Forage Laboratory. (1995). Tables of feed composition. Ithaca, NY.
O'Quinn, P. R., Knabe, D. A., & Gregg, E. J. (1997). Efficacy of natuphos in sorghum-based diets of finishing swine. Journal of Animal Science. 75, 1299-1307.
Palmquist, D. L., & Jenkins, T. C. (1980). Fat in lactation rations: review. Journal of Dairy Science. 61(1), 1.
Perdok, H. B., & Leng, R. A. (1987). Hyperexcitability in cattle fed ammoniated roughages. Animal Feed Science and Technology. 17, 121-143.
Perney, K. M., Cantor, A. H., Straw, M. L., & Herkelman, K. L. (1993). Poultry Science. 72, 2106.
Piepenbrink, M. S. & Overton, T. R. (2003). Liver metabolism and production of cows fed increasing amounts of rumen-protected choline during the periparturient period. Journal of Dairy Science. 86, 1722-1733.
Ruppel, K. A., Pitt, R. E., Chase, L. E., and Galton, D. M. (1995). Bunker silo management and its relationship to forage preservation on dairy farms. Journal of Dairy Science. 78, 141-153.
Satter, L. D. (1994, October 18). Use of heat processed soybeans in dairy rations (pp. 19-28). Proceedings Cornell Nutrition Conference for Feed Manufacturers, Rochester, NY.
Undersander, D., Martin, N., Cosgrove, D., Kelling, K., Schmitt, M., Wedberg, J., Becker, R., Grau, C., Doll, J., & Rice, M. E. (1994). Alfalfa management guide. Published by American Society of Agronomy, Inc.; Crop Science Society of America, Inc.; Soil Science Society of America, Inc. Produced at Cooperative Extension Publications, University of Wisconsin-Extension.
USDA Center for Animal Health Monitoring. USDA: APHIS: VS. Centers for Epidemiology and Animal Health, Fort Collins, CO. Retrieved October 13, 2003 from http://www.aphis.usda.gov/vs/ceah/cahm
USDA. (1987). The official United States standards for grain. Washington, DC: Federal Grain Inspection Service.
Table 3-1 Guide to feedstuff nomenclature Classification 1 2 3 Species, Alfalfa Orchard- Corn variety or grass- kind Ryegrass Part eaten Hay Aerial part Aerial part Process(es) Sun Fresh Ensiled and cured treatment(s) Stage of Early Immature Well maturity bloom eared Cutting or crop Cut 1 -- -- Grade, quality -- -- -- or guarantees IFN 1-00-108 2-03-472 3-02-823 Classification 4 5 6 Species, Oats Soybean Magnesium variety or oxide kind Part eaten Grain Seeds -- without hulls Process(es) Rolled Solvent- -- and extracted, treatment(s) ground Stage of -- -- -- maturity Cutting or crop -- -- -- Grade, quality -- Maximum -- or 3% guarantees crude fiber IFN 4-03-307 5-04-612 6-02-756 Classification 7 8 Species, Yeast, Lignin variety or brewers sulfonate kind Saccha- romyces Part eaten -- -- Process(es) Dehydrated, Dehydrated and ground treatment(s) Stage of -- -- maturity Cutting or crop -- -- Grade, quality -- -- or guarantees IFN 7-05-527 8-02-627 From National Research Council. (1972). Atlas of nutritional data on United States and Canadian feeds. Washington, DC: National Academy Press. Table 3-2 Average legume and grass nutrient analyses values Number of CP Feedstuff observations CP ADF NDF NEI All legume 4697 19.4 32.5 41.2 0.64 Mixed, mostly legume 3649 16.4 36.7 51.3 0.56 Mixed, mostly grass 3819 12.1 39.3 60.5 0.53 All grass 3343 10.6 38.7 64.8 0.5 Feedstuff DE Ca P Mg K All legume 0.99 1.46 0.25 0.29 2.58 Mixed, mostly legume 0.91 1.14 0.25 0.26 2.26 Mixed, mostly grass 0.87 0.75 0.23 0.23 1.93 All grass 0.83 0.55 0.22 0.21 1.84 From Northeast DHIA Forage Laboratory. (1995). Tables of feed composition. Ithaca, NY. CP: Crude protein; ADF: acid detergent fiber; NDF: neutral detergent fiber; NEI: net energy for lactation; DE: digestible energy; Ca: calcium; P: phosphorous; Mg: magnesium; K: potassium. Table 3-3 Plants that may be lethal when ingested by livestock Common name Botanical name Agent Arrow grass Triglochin maritime Cyanide (HCN) Blue flax Linum spp. Cyanide Chokecherry Prunus virginiana Cyanide Elderberry Sambuccus spp. Cyanide Johnson grass (Sudan) Sorghum halepense Cyanide Poison suckleya Suckleya suckleyana Cyanide Serviceberry Amelanchier alnifolia Cyanide Johnson grass Sorghum halepense Nitrate Kochia weed Kochia scoparia Nitrate Lamb's quarter Chenopodium spp. Nitrate Nightshades Solanum spp. Nitrate Pigweed Amaranthus spp. Nitrate Russian thistle Salsola rali Nitrate Sunflower Helianthus spp. Nitrate Death camas Zigadenus spp. Alkaloid Water hemlock Cicuta spp. Alkaloid Beet tops Beta vulgaris Oxalates Curly leafed dock Rumex crispus Oxalates Greasewood Sarcobatus vermiculatus Oxalates Halogeton Halogeton glomeratus Oxalates Milkweeds Halogeton glomeratus Oxalates Osalis, "shamrock" Oxalis spp. Oxalates Pigweed Amarantus spp. Oxalates Rhubarb Rheum rhaponticum Oxalates Yew Taxus spp. Cyanide From American Sheep Industry Association, Inc. (1996). Sheep production handbook (pp. 384-385). Denver, CO: C&M Press. Table 3-4 Plants causing photosensitization in livestock Common name Botanical name Agent Bishop's weed Ammi majus Primary Buckwheat Tagopyrum sagittatum Primary Dutchman's breeches Thamnosma texana Primary Rain lily Cooperia peduniculda Primary Spring parsley Cymopterus watsoni Primary St.John's wort Hypericum perforatum Primary Agave Agave lechuguilla Secondary Horsebrush Tetradymia spp. Secondary Klein grass Panicurn coloradatum Secondary Kochia Kochia spp. Secondary Lantana Lantana spp. Secondary Sacahuiste Nolina texana Secondary From American Sheep Industry Association, Inc. (1996). Sheep production handbook (pp. 384-385). Denver, CO: C&M Press. Table 3-5 Plants affecting the nervous system of livestock Common name Botanical name Agent Bitterweed Hymenoxys spp. Semiarid regions in U.S. Black henbane Hyoscyamus niger Northern Rocky Mts. Black nightshade Solanum migrum Eastern U.S. Deadly nightshade Atropa belladonna Cultivated in gardens Fitweed Corydalis caseara Intermountain U.S. Horse nettle Solanum carolinense Texas/Atlantic coast Jimson weed Datura stramonium Florida to Texas Locoweed Oxytropis spp. Western U.S. Locoweed Astragalus spp Western U.S. Lupine, bluebonnet Lupinus spp North America Paper flower Psilostrope spp Southwestern U.S. Rayless goldenrod Isocoma wrightii Western U.S. Silverleaf nightshade Solanum eleagnifolium Southwestern U.S. Snakeroot Eupatorium rugosum Eastern U.S. Twin leaf senna Cassia occidentalis U.S. Wheat Triticum aestivum U.S. From American Sheep Industry Association, Inc. (1996). Sheep production handbook (pp. 384-385). Denver, CO: C&M Press. Table 3-6 Pasture's low dry matter content, low energy density and the increased energy requirement associated with grazing activity make it difficult for the pastured animal to physically ingest the pounds of feed needed to deliver the energy to support high production Feedstuff Energy Feedstuff DM content, Mcal/lb. Feedstuff content % NEI, DM basis Energy supplied by a mix of feedstuffs to a confined cow (energy required by a confined cow to make 85 lb. is assumed to be 36.9 Mcal NEI) Corn grain 88.1 0.9 Soybean meal 89.5 1.0 Corn silage 35.1 0.6 Grass silage 42.0 0.5 Energy supplied by pasture without supplementation to a pastured cow (energy required by a pastured cow to make 85 lb. is assumed to be 47.7 Mcal NEl) Pasture 20.1 0.7 Lb., as fed (DM) in a ration Feedstuff Energy supporting 85-lb. (Mcal NEI) Feedstuff milk production contribution Energy supplied by a mix of feedstuffs to a confined cow (energy required by a confined cow to make 85 lb. is assumed to be 36.9 Mcal NEI) Corn grain 22 (16.8) 16.8 Soybean meal 6.8 (5.8) 5.8 Corn silage 32 (11.2) 7.0 Grass silage 35 (14.7) 7.3 Totals: 95.8 (48.5) 36.8 Energy supplied by pasture without supplementation to a pastured cow (energy required by a pastured cow to make 85 lb. is assumed to be 47.7 Mcal NEl) Pasture 346 (68.34) 47.7 DM: Dry matter; NEI: net energy for lactation (dairy). Values taken from software provided by the Dairy NRC. The feedstuff NEI values shown here are for comparison purposes only. The Dairy NRC does not calculate ration NEI directly from feedstuff NEI values. Table 3-7 Adjustment factors for pasture dry matter intake Daily Forage Allowance Pasture Dry Matter Available, lb/acre 4 3 2 1 Pasture intake adjustment factor 100 0.21 0.18 0.17 0.15 200 0.37 0.33 0.32 0.26 300 0.51 0.46 0.44 0.37 400 0.64 0.57 0.55 0.46 500 0.74 0.67 0.64 0.54 600 0.83 0.75 0.72 0.60 700 0.90 0.81 0.78 0.65 800 0.95 0.86 0.82 0.69 900 0.99 0.89 0.85 0.71 1,000 1 0.90 0.86 0.72 1,500 1 1 0.98 0.82 2,000 1 1 1 0.92 From Fox, D. G., Tylutki, T. P., Van Amburgh, M. E., Chase, L. E., Pell, A. N., Overton, T. R., Tedeschi, L. O., Rasmussen, C. N., & Durbal, V. M. (2000). The net carbohydrate and protein system for evaluating herd nutrition and nutrient excretion (CNCPS vol. 4.0. p. 212). Animal Science Department Mimeo 213, Cornell University, Ithaca, NY. Table 3-8 Harvest recommendations Length of Cut Crop Maturity (inches) Corn silage milk line 1/2 to 2/3 3/8-1/2 Small grain silage milk to soft dough 1/4-3/8 Hay crop silage Early bloom 1/4-3/8 High moisture After physiologi- -- grain cal maturity Silo Type Horizontal Conventional Sealed & Bag Upright Upright Crop Dry Matter Content (%) Corn silage 28-33 32-37 40-50 Small grain silage 30-40 30-40 30-40 Hay crop silage 30-35 35-40 40-50 High moisture 65-72 70-75 74-78 grain Table 3-9 A formula and analysis of a trace mineralized salt block Nutrient Type of Guarantee Concentration Sodium chloride Maximum 97.00% Sodium chloride Minimum 95.00% Zinc Minimum 0.600% Manganese Minimum 0.330% Iron Minimum 0.240% Copper Minimum 0.340% Iodine Minimum 0.130% Cobalt Minimum 0.120% Ingredients Salt, zinc oxide, manganous carbonate, iron sulfate, copper sulfate, potassium iodide, cobalt carbonate, mineral oil, and cane molasses.
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|Author:||Tisch, David A.|
|Publication:||Animal Feeds, Feeding and Nutrition, and Ration Evaluation|
|Date:||Jan 1, 2006|
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