Feeding the dairy herd
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Feedstuffs are often classified as forages and concentrates, but these divisions are not always clearly definable. Concentrates usually mean high quality, low fiber feeds and include the cereal grains, milling by-products, protein sources, and fats. Concentrates have a high digestible energy content per unit of weight or volume. The energy is derived mostly from starches, sugars, other readily available carbohydrates, and fats or oils. Forages are characterized by being more fibrous (greater than 20 percent ADF) or bulky and generally represent the vegetative portion of a plant. The digestible energy content of forages is usually lower per unit weight or volume than concentrates, with most of the energy derived from cellulose or hemicellulose. Classification problems arise with high quality, immature forages, as these are more like concentrates than forages. For example, bud stage alfalfa with 24 percent ADF and 36 percent NDF is classified as a forage, while beet pulp with 33 percent ADF and 54 percent NDF is classified as a concentrate.
Legumes and grasses. Legumes and grasses are a major source of forage for dairy animals. These forages are excellent sources of protein, carotene, calcium, and other minerals if harvested and stored properly. High quality forages can make up as much as two-thirds of the ration DM, with cows consuming 2-1/2 to 3 percent of their body weight in forage DM. High quality forages fed in balanced rations will supply much of the protein and energy needs for milk production.
Important considerations in harvesting alfalfa and grasses are cutting date and stage of maturity. With advancing maturity, plants decrease in protein, energy, calcium, phosphorus, and digestible DM, while increasing in fiber. As fiber, NDF, and especially ADF, increases, the lignin content of the plant also increases. Lignin is indigestible and makes other nutrients less available.
Legumes and grasses can be harvested as low-moisture silage, haylage, or as hay. Silage and haylage offer the advantages of less leaf loss, less time for field curing, and usually, reduced labor in harvesting. Legume-grass silage should be put up at 35 to 40 percent DM in a bunker silo, haylage at 40 to 50 percent DM in a stave silo, and 50 to 60 percent in an oxygen-limiting silo. If too wet, undesirable fermentations develop and cattle eat less feed. Forage ensiled too dry does not ferment properly and can mold or heat excessively. Legume or grass silages should be chopped (3/8-inch theoretical length of chop—TLC) and at proper moisture for ensiling. Rapid filling, good packing, and sealing are additional keys to good preservation.
Hay should not be baled or stacked until the DM content is at least 80 percent. Otherwise, heating and molding can develop.
Legume and grass haylages and wet hay can heat excessively and lose feeding value. Prolonged and excessive heating is indicated by a brownish, caramelized appearance. It causes protein to join with carbohydrate, lowering available protein and energy in the feed. Crude protein analyses do not reflect changes in available protein; therefore, an available protein test must be run. Heat damage, which can occur in any kind of storage structure, can be avoided or reduced by keeping silos in good repair and harvesting, ensiling, and storing the crop using good management practices.
Corn silage. Good corn silage contains nearly 50 percent grain on a DM basis. It is an excellent source of energy for dairy cattle. If it is properly made, cows will eat large amounts of this feed. Corn silage requires protein and mineral supplementation to be balanced for high milk production.
To attain maximum yield, corn should be harvested for silage when it has reached physiological maturity: kernels are fully dented, milk line is 1/2 to 2/3 down from the crown and cells at the base of the kernel (when dissected) are turning black. DM content should be approximately 35 percent (ear is 55 to 60 percent DM when the whole plant is 32 to 38 percent DM). Immature corn silage is usually wetter, below 32 percent DM, and yields less total dry feed per acre. Seepage losses from the silo occur when material below 32 percent DM is ensiled. If corn becomes too dry before ensiling, field losses are greater and the feed may not ensile as well (poor compaction, molding, and lower palatability).
Sorghum silage. Sorghum can be used for silage in areas adapted to 95-day relative maturity or longer corn hybrids. Forage sorghum equals corn in yield, but grain sorghum usually does not yield as well as corn except during drought conditions. Energy and intake potential are lower than with corn silage.
Small grains. Oats, barley, triticale, wheat, and rye can be harvested as forage, although yield per acre is usually less than corn, legume, or grass forages. Harvest in the boot stage for highest quality. Delaying harvest until soft dough increases DM yields, but reduces quality. Peas or beans can be included with small grains to increase protein content. These crops should be wilted to 60 percent moisture before ensiling.
Straws. Oat, barley, and wheat straws are low in energy, protein, minerals, and vitamins. They should be limited in rations for lactating cows and used only when additional fiber is needed. If adequately supplemented, some straw can be used for dry cows and older heifers.
Stover. Corn stover, properly supplemented, can be used in heifer and dry cow rations. It is low in protein and energy, and therefore, is not recommended for feeding to milk cows.
Pastures. If well managed, pastures are a good source of nutrients. They have the added advantage of eliminating feed handling and manure hauling. Proper fertilization and management is necessary to maintain a good pasture. Trampling is a problem and results in nutrient wastage. Moving cattle and maintaining fences are major disadvantages. Frequent rotations of small lots reduce loss, but require more labor. Large herds are not handled easily in pasture situations. Additional grain is needed for high-producing cows. As quantity and quality of pasture changes during the summer, cattle need to be supplemented with stored forages and other feeds.
Green chop. Harvesting feeds by field chopping and feeding immediately has the advantage of reducing field losses. However, cutting every day can be a major problem during wet weather or during peak work periods.
Forage evaluation. The nutrient content of forages can vary greatly. Stage of maturity, species composition, harvesting conditions and methods, growing conditions, moisture content at harvesting, and storage all affect nutrient content. To achieve optimum production from forage-based rations, the nutrient content of forage must be known and rations formulated to account for forage nutrient contributions and deficiencies.
The minimum forage tests required for determining forage nutrient composition are: DM, CP, ADF, NDF, calcium (Ca), and phosphorus (P). Heat damaged or caramelized forages should be tested to determine losses in CP available to the animal. These losses are not shown in a CP analysis alone. An adjusted crude protein (ACP) corrected for heat damage losses should be used in ration formulation.
Knowing DM is necessary for determining DM intake of animals and evaluating storage problems. Forages ensiled too wet reduce intake and have a butyric acid fermentation. Ensiling too dry results in heat damage.
Crude protein is a mixture of true protein and NPN. Nitrogen analysis times 6.25 equals CP. Adjusted crude protein (ACP) is the amount of crude protein available to the animal. In most forages, 12 percent or less of the total CP is unavailable. If no heat damage or protein loss to the animal has occurred, CP and ACP are equal.
Acid detergent fiber is highly related to digestibility. As ADF increases, digestible DM (DDM) or TDN and energy content of forages decline. Estimates of digestibility and energy content of forages can be made from ADF using the following equations (DM basis):
- Legumes and grasses:
- TDN (%) or DDM (%) = 88.9 – (ADF% x .779)
- NEL (Mcal/lb) = 1.044 – (ADF% x .0123)
- Corn silage:
- TDN (%) = 87.84 – (ADF% x .7)
- NEL (Mcal/lb) = 1.044 – (ADF% x .0132)
Neutral detergent fiber, or cell walls, is a good predictor of forage intake. The potential DMI, as a percentage of body weight, of a forage when fed alone can be estimated from:
|DMI (% of BW) =||120
Forage NDF% (DM basis)
Relative feed value (RFV) incorporates quality factors calculated from ADF and NDF into a useful index for comparing legume and legume-grass mixtures. The higher the RFV, the higher the quality and production potential of the forage. High-producing cows should be fed forages with a RFV of 120 or higher. A forage containing 41 percent ADF and 53 NDF is considered to have an RFV of 100. The equation to calculate RFV is:
|RFV =||DDM x DMI
A representative sample of the feed is critical for testing. For hay, a minimum of 15 bales (18 to 20 optimal) should be sampled from different locations in the stack. A sampling probe or bale core is needed to obtain representative samples. Haylage or silage samples are best obtained at the time of ensiling. Two or three grab samples from every other load during silo filling will provide a representative quantity for mixing and further subsampling. Grab samples should be refrigerated during collection to prevent deterioration and change in chemical composition. Combine all grab samples, mix well, and remove one quart of material for testing. Heat damage can only be tested on feeds after ensiling.
Energy Concentrates (Grains and By-Product Feeds)
The main nutrient contribution of grains and by-product feeds is energy. Oats and barley are moderately high in CP. Processing grain (rolling, crimping, cracking, or grinding) increases its digestibility when fed to cows. As much as 30 percent of the whole grain will pass through cows intact if the grain is not processed before feeding. Breaking the seed coat increases digestion. Coarse-textured, processed grain enhances palatability and intake. Fine grinding of grain can increase digestibility, but can also lower milk fat percent and cause rumen acidosis. Pelleted grain is not dusty, and may increase palatability and intake, but has the same disadvantages as finely ground grain on rumen fermentation. Because young animals chew their feed more thoroughly than adults, whole grains can be fed up to 12 months of age.
Barley is a good source of energy and protein. If barley is used in large amounts in dairy cattle rations, cattle should be adjusted gradually. Rolling is superior to fine grinding for palatability. If barley is finely ground, it shouldn't make up more than 50 percent of the grain ration.
Beet pulp can be obtained either in plain form or as molasses beet pulp. It is relatively high in energy, adds highly digestible fiber and bulk to diets, and enhances palatability. Maximum feeding rate is 30 percent of the ration DM.
Cottonseed, whole or fuzzy, is a medium protein, high fat, high fiber, and high energy feed. Whole cottonseed is white and fuzzy, while de-linted cottonseed is black and smooth in appearance. The amount fed should not exceed 7 pounds per cow per day.
Corn gluten feed is a relatively high fiber, medium energy, medium protein by-product of the corn wet milling industry. The by-product is sold as either a dry or wet product. Corn gluten feed (wet or dry) should not exceed 25 percent of the total ration DM.
Corn, ear or corn and cob meal is a relatively high energy feed relished by cows. It contains 10 percent less energy than shelled corn. However, the fiber supplied by the cob aids in maintaining fat test and keeping cows on feed.
Corn, shelled is the most common grain fed to dairy animals. It is one of the highest energy feeds available for use in dairy rations. Where corn can be grown successfully, it is generally an economical source of energy. Because of its high caloric density, good management (determining the amount to feed, frequency of feeding, mixing with other feeds, etc.) is needed to obtain maximum consumption without causing digestive disturbances.
Corn, high moisture offers these advantages:
- Grain can be harvested 2 to 3 weeks earlier, reducing field losses and harvest problems associated with adverse weather.
- Storage and handling losses are reduced.
- It fits automated feeding programs.
- The expense of drying grain is eliminated.
- Grain is highly palatable.
- Daily labor of grain processing or grinding is reduced.
High moisture ear corn should be stored from 28 to 32 percent moisture and processed prior to storage. The wet cob is more digestible than the cob in dry corn.
High moisture shelled corn should be stored within a moisture content of 25 to 30 percent. In airtight silos, the shelled corn can be stored whole or ground, and rolled upon removal from the silo. In conventional silos, bags or bunkers, it should be processed (ground or rolled) before storing. Propionic acid can be used effectively to treat and preserve high moisture corn for dairy cattle.
Hominy feed is a fine, dusty ground corn feed from which the bran and gluten have been removed. It is the by-product from the manufacture of hominy grits. Fat content is generally about twice that of corn grain, but quite variable. Hominy can replace corn in the diet, but is low in starch.
Fat is a concentrated energy source. Several kinds of animal and vegetable fats or oils are available for feeding. Amounts to feed and responses from feeding will vary with fatty acid (saturated or unsaturated) composition of the fat. Total added fat in diets should not exceed 4 percent (DM basis) with animal, vegetable or rumen inert fats individually not exceeding 2 percent.
Molasses (cane and beet) supplies energy and is used primarily to enhance the acceptability of the ration. The amount used should be limited to 5 to 7 percent of the grain mix (10% in pelleted feeds) to maintain flow characteristics in automatic feeding equipment and to avoid undesirable rumen effects.
Oats contain 15 percent less energy but 20 to 30 percent more protein than shelled corn. The advantage of adding oats to dairy rations is that it adds fiber and bulk, and may help maintain rumen function.
Screenings are often an economical buy. However, they vary in protein and energy content, can be unpalatable, and in some instances are difficult to digest.
Sorghum grain or milo can be used to replace corn in diets. The energy content is about 90 percent that of corn, and protein content is variable (7 to 12 percent CP). Milo must be ground before feeding to prevent whole seed passage, but grinding lowers palatability because of dustiness.
Soybean hulls, soybean flakes, or soyhulls are all similar feeds. All are good sources of highly digestible fiber and may replace starch in the diet, but not forage fiber. Limit amounts to 33 percent of the grain ration.
Wheat is not used often because price is usually too high. It is acceptable in dairy cattle rations in reasonable amounts (less than 50 percent of the grain ration). It is high in energy and relatively high in protein. Cattle should be adjusted slowly to rations containing wheat.
Wheat bran is included to add bulk and fiber to the diet. It is relatively high in protein and phosphorus, improves ration palatability, and functions as a laxative.
Wheat midds consist of fine particles of wheat bran, wheat shorts, wheat germ, and other products from the wheat milling process. Midds are a moderate source of protein and energy, and must not contain more than 9.5 percent crude fiber. Grain rations with more than 20 percent midds have decreased milk production.
Whey (dried and liquid) can be fed to dairy cattle. Dried whey can be added to grain mixtures up to 10 percent of the mix. Dried whey also can be added to forages at the time of ensiling at a rate of 20 to 100 pounds per wet ton of forage. Liquid whey can be offered to cattle on a free choice basis. Because liquid whey is over 90 percent water, 15 to 25 gallons need to be consumed daily to obtain substantial amounts of DM. Whey contains large quantities of lactose (milk sugar) and small amounts of protein and minerals. Liquid whey should not be over 36 hours old because it will become acidic and cattle will not drink it. Flies can be a problem if strict sanitation is not practiced.
Bloodmeal is dried blood from animal processing plants. Spray or ring dried bloodmeal is superior to batch dried because less heat damage occurs. Bloodmeal is high in true protein, UIP and the amino acid lysine. Limit the amounts fed to less than 1 pound per cow per day and do not feed in diets high in moisture, as palatability can become a problem.
Brewers grain, a by-product of the beer industry, is available dry or wet. Wet brewers grains contain 70 to 80 percent water. Feeding more than 20 percent of the ration DM or 40 to 50 pounds of wet feed per cow has been shown to reduce intake and milk production. On a DM basis, brewers grains are high in protein and a fair source of energy.
Canola meal is a relatively new high-protein supplement produced from the crushing of canola seeds for oil. New varieties of canola, previously called rapeseed, are low in goitrogenetic compounds. Canola meal can be substituted for soybean meal in diets.
Corn gluten meal is produced from wet milling of corn for starch and syrup. Two corn gluten meals are produced, a 40 percent and 60 percent CP supplement, with the 60 percent being the most common. Both supplements are good sources of UIP. Energy content of corn gluten meal is only slightly less than corn grain. Limit amounts to 5 pounds per cow per day because of palatability problems.
Cottonseed meal is a high protein by-product from the extraction of oil from whole cottonseed. It is quite palatable, but may be variable in CP content. Cottonseed meal and other cottonseed products can contain a toxic substance known as gossypol. Limit the total amount of cottonseed products in diets to 8 pounds per cow per day or less.
Distillers dried grains, with or without solubles, is a by-product of grain fermented for alcohol production. Corn is the most common grain fermented, but other grains are used, and the composition of the distillers grains will vary depending on grain source. Dried distillers grains are moderate sources of CP (23 to 30 percent), but a good source of UIP if not heat damaged.
Feather meal is hydrolyzed poultry feathers. High quality feather meal is both high in CP (85 to 92 percent) content and digestibility, but low in several important amino acids. Feather meal is rather unpalatable and should be introduced into diets gradually and limited to 1 to 1.5 pounds per head per day. Combinations of feather meal and blood meal are recommended for balanced amino acid supplementation.
Fishmeal is a by-product of the fish industry. It includes bones, head, trimmings, and fish parts. Quality can vary, depending on source and handling. Fish oil reduces fiber digestion in the rumen, and should be limited to 50 grams per day. Limit fish meal to 1 to 2 pounds per day.
Linseed meal is a product of the flax industry and is a good protein supplement (39 percent). It is very palatable and can be used as a replacement for soybean meal.
Malt sprouts consist of dried sprouts and rootlets produced during the malting (sprouting) of barley for beer. The feed is similar to dried brewers grain, especially in UIP, but bitter tasting, reducing palatability. Limit amounts in the diet to less than 5 pounds per cow per day or 20 percent of the grain mix.
Meat and bone meal is a rendered and dried product from animal tissue. It does not contain horn, hide, hair, manure, or stomach contents. Meat and bone meal is a good source of CP, UIP, calcium and phosphorus. Limit amounts fed to 2.5 pounds or less per day. Meat and bone meal needs to be handled properly and stored in dry places to avoid salmonella contamination.
Soybeans are an excellent source of CP and fat (18 percent) for dairy cattle. Raw soybeans can be fed up to 5 pounds per cow per day. Cows should be adjusted to beans gradually to avoid diarrhea and off-feed. Raw beans contain urease, an enzyme that releases ammonia from urea when soybeans and urea are mixed together. Urea and raw beans should not be mixed and stored together. Microbial degradation in the rumen reduces anti-protein factors in raw beans (trypsin inhibitor, for example). Roasting, extruding, or other heat processing reduces anti-protein factors and urease activity and increases UIP value of the soybeans. Heating temperature (290 to 300 degrees F) and steeping time (30 to 45 minutes) must be carefully controlled to avoid under- or overheating soybeans. Heat-treated soybeans can be fed up to 8 pounds per day. Cost of processing, including bean shrinkage, should be evaluated.
Soybean meal is the most common and usually the most economical vegetable protein supplement. The most common soybean meal contains 44 percent CP as fed. Two other sources of soybean meal are: dehulled soybean meal (48 percent CP), and expeller or old processed soybean meal (42 percent CP and 5 percent fat). Many commercial supplements contain substantial amounts of soybean meal.
Sunflower meal protein supplements range from 28 to 45 percent protein. The protein percentage varies inversely with fiber percentage: lower protein, higher fiber. Sunflower meal is a good source of protein and phosphorus. Palatability problems have been observed in some herds when sunflower meal is topdressed.
Urea is a NPN compound containing about 46 percent N. It has a protein equivalent of 287 percent (46 percent N x 6.25). It is a good source of SIP. Urea fits best in diets high in carbohydrate energy (grains and corn silage), low in protein, and low in SIP. Limit amounts fed to .4 pounds per cow per day, 1 percent in grain mixes, or 0.5 percent in corn silage (10 lb/ton added at ensiling). If urea or another NPN source like ammonia is added to corn silage, the amount of urea included in a grain mix should be reduced so that the intake of urea or urea equivalency does not exceed the maximum of .4 pounds per cow per day. Urea is not a palatable feed and should be mixed thoroughly into the grain mix or silage. Urea is best utilized when incorporated into total mixed rations (TMR) and/or fed frequently in mixtures with other feeds.
Urea can be used in making up a high-protein concentrate. A mixture of 87 pounds of ground shelled corn and 13 pounds of urea is equivalent in energy and crude protein to 100 pounds of soybean meal. A mixture of 56 pounds of ground shelled corn, 7 pounds of urea, and 37 pounds of soybean meal also equals 100 pounds of soybean meal in total energy and protein equivalent, and can be used as a substitute for soybean meal. However, it should not be used as a protein topdress because of bitter taste and possible feed refusal. When fed according to recommendations, urea is a good CP source and has not been shown to affect reproduction efficiency.
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