Concentrates are low-fiber, high-energy feeds when compared to forages and they can vary considerably in their protein content. Most often they are fed to raise the energy level of the ration for dairy cattle and to compensate for any other deficiencies that remain beyond those provided by the forage portion of the ration.
Energy sources for dairy cattle can be broken down into starch, sugar, and fat. They can be analyzed in individual ingredients, grain mixes and total mixed rations. However, due to specific analysis procedures, there may be added costs for each depending on the testing package selected.
Starch is the primary source of energy in dairy rations. The source and processing method of the starch will determine how it will be digested in the rumen. Cereal grains like corn provide most of the starch in dairy cattle diets. Of the energy sources, improper starch feeding, such as type and amount can have the greatest negative impact on rumen function.
Sugars are readily available to the rumen microorganisms. Simple sugars include glucose, fructose, and sucrose. To increase the amount of sugar in the ration, ingredients like liquid molasses or citrus pulp can be fed.
Fats can come from both plant and animal sources. They are very energy dense compared to carbohydrates and protein. Fatty acid profiles of ingredients are important as they can have negative effects on fiber digestibility and animal performance. Unsaturated fat is highly digestible but may reduce fiber digestibility in the rumen compared to saturated fat that has less impact on fiber digestion. Like starch, fat digestibility can be affected by source, physical nature, and its chemical composition. Protected fats are available, and they have been designed to bypass the rumen eliminating risks to rumen function.
Protein has several components; some can be tested, and others cannot. Metabolizable protein is mainly used in ration formulation software programs. Metabolizable protein is defined as the true protein that is digested in the abomasum (post-ruminally) and its amino acids are absorbed by the small intestine. Amino acids are the essential components that form proteins and are the required nutrients for cows. Ingredients like soybean meal and canola meal are very good sources of amino acids.
Even though crude protein is an older approach to ration formulation, it is analyzed by labs and still has value when comparing feed ingredients to book values or comparing formulas to the actual mix. However, crude protein only reflects the nitrogen content of the feed and not how it is used by the animal.
Protein can be broken down into several fractions in ration formulation programs: degradable and undegradable protein and soluble protein. Degradable protein is digested in the rumen. Soluble protein is very rapidly digested in the rumen. Undegradable protein is that fraction bypassing the rumen. All these fractions are important and require the proper balance to keep the rumen microbes functioning properly. Soluble protein is most routinely analyzed by testing labs. Degradable protein can be an analyzed value, or it can be an estimate based on NRC (2001) values This can vary across testing labs.
The other nutrients in concentrates include fiber, minerals, and vitamins. The main fiber components are neutral detergent fiber (NDF) and acid detergent fiber (ADF). Most byproduct feeds contain substantial fiber levels compared to the cereal grains. The macro-minerals are calcium, phosphorus, magnesium, potassium, sodium, sulfur, and chloride. The micro-minerals are manganese, copper, zinc, iron, selenium, cobalt, and iodine. All minerals can be analyzed at testing labs. It is recommended that byproduct feeds be tested for their mineral content as their levels can vary depending on the source. The fat-soluble vitamins are A, D, and E. Vitamins are not typically analyzed in grains.
Palatability of grain mixes or commodities is important for attaining the required levels of feed intake. Proper processing, storage, and attention to particle size are important for palatability and ruminal degradation of nutrients. The manner of feeding and the processing method can influence intakes. For example, finely ground corn incorporated into a TMR may not create intake problems but if fed conventionally (e.g., top-dressed or fed as a single feed) may limit intake and/or cause digestive upsets. Pelleted grains that contain a lot of fines may cause problems in robotic feeders compared to incorporation into a TMR. Feeding management in addition to nutrient content should be considered when formulating rations.
The three-basic groups for concentrate ingredients are cereal grains, protein sources, and by-product feeds. The feed type and the manner of preparation influence how the dairy cow uses these ingredients. The objective is finding the balance of energy, protein, and micronutrients that best compliment the forage ration. It is recommended to find the best cost ration versus the least cost ration.
The cheapest ration is not necessarily the best cost ration. Cows prefer consistency and constantly switching ingredients based solely on price may not be the best strategy. That is why using income over feed cost to monitor performance is recommended because it considers both production and feed cost. Also, depending on the concentrate ingredient fed, there can be substantial nutrient variation. St-Pierre et. al. (2015) evaluated variation in nutrient composition of common feeds and mixed diets on commercial dairy farms. The ingredients having the most variation on farm and where regular testing was recommended was for wet corn gluten feed, wet brewers' grains, wet distillers' grains, and high-moisture corn. Farms feeding ingredients like dry corn grain, soybean meal, dry corn gluten feed, canola meal, and whole cottonseed were not a source of significant variation. Dried distillers' grains could be a source of variation depending on the plant of origin. Ingredient variation could affect maintaining the appropriate balance of nutrients if there is a lot of variability in feedstuffs.
Barley, corn (shelled or ear), milo (sorghum), oats, rye, triticale, and wheat are the most common cereal grains. The general nutritive characteristics of these grains are that they are high in net energy, and low in fiber and protein. They are similar in their level of phosphorus when compared to forages and are low in calcium.
Corn is more commonly fed compared to the other cereal grains. Corn is fed either as shelled corn or ear corn, which the latter is comprised of 20 to 25 percent cob and 70 to 80 percent grain if partitioned by weight. Due to palatability problems with rye, triticale, and wheat, limited amounts should be fed in rations for dairy cattle (Table 1).
The energy that cereal grains supply comes in the form of mainly starch with minimal levels of fats and sugars. The availability and rate of digestion of the starch depends on the grain source and processing method. The rate of digestion for the following grains is ranked from slowest to fastest: milo, corn, barley, wheat, and oats.
The method of processing grains influences the rate and extent of digestion in the rumen. Starch in finely ground grains is degraded more rapidly by ruminal microorganisms than coarsely processed grain. Finely ground grains are higher in digestibility because there is more surface area for the rumen bacteria to attach. The starch in high-moisture grains ferments more rapidly in the rumen than starch in dry grain. High-moisture grains should be fed rolled versus whole to optimize starch utilization by the rumen bacteria. Heating grains, such as steam flaking (24 to 28 pounds/bushel), enhances starch digestion. Steam-flaked grains should be rolled to a thin flake. The heating process gelatinizes the starch in a manner that increases fermentability in the rumen. By increasing starch utilization, the lactation performance of the cow can improve and may reduce feed costs, especially when grain costs are high.
Most protein sources come from either plant or animal origin. Common plant protein sources used in dairy rations are soybean meal and canola meal. Animal protein sources include blood meal and meat and bone meal (porcine source). The protein fractions can vary widely depending on the ingredient. Soybeans are the most common ingredient producers raise on farm. Typically, the beans are roasted providing a source of undegradable protein and they also contain a high fat content. These ingredients are high in protein quality and are essential when formulating concentrate mixtures.
Protein quality refers to the types, amounts, and ratios of peptides (short strings of amino acids) and amino acids that are in a feedstuff. Therefore, it is recommended to feed various protein sources, so cows receive adequate levels, both ruminally and post-ruminally, of the essential and limiting amino acids (e.g., lysine and methionine).
Urea is the exception because it is not a protein supplement, but a source of nitrogen. This nitrogen is converted to ammonia, which is used by the rumen bacteria for protein synthesis. Urea works well in mixtures with plant proteins if soluble protein is needed. Compared to plant and animal proteins, urea is often lower in price.
There are numerous sources of protein supplements available to producers that can be fed to meet an animal's requirement for metabolizable protein. Limitations on some of these sources may be for palatability reasons and keeping the protein fractions within the recommended ranges.
By-product feeds are the secondary materials generated in addition to the principal product being manufactured for human consumption. The most common by-products are derived from cereal grains.
The process used to produce the by-product feed will determine how it can be used in the formulated ration. Some contain high levels of fat, which can make a diet more energy dense. Others may supply undegradable, degradable, or soluble protein at various levels. Other commodities may contain relatively high fiber levels and are used to balance rations for total NDF (e.g, cottonseed hulls, soyhulls). Mineral levels can vary and should be tested. Some bakery products (e.g., cookie meal, donuts) may contain high levels of sodium and chloride and these should be included in the analysis.
Some by-product feeds are available in wet form, such as brewers and distiller's grains. Higher variability in moisture content may necessitate periodic testing of dry matter and nutrient content. These products are usually economical if trucking costs are not prohibitive. When adding by-product feedstuffs into the ration, consistency of the nutrient composition is key. Due to the high variability of various by-product feed sources producers may be hesitant to add them into the diet, therefore, laboratory analysis may be necessary with each delivery of feed to ensure nutrient consistency.
Feeding by-products can decrease the number of human-edible feedstuffs that are used to feed cattle, which is an important sustainability concern due to the growing human population. To study this concept, Ertl et al. (2016) investigated the effects of completely substituting common cereal grains and beans with a mixture of by-product feeds (wheat bran and sugar beet pulp) in a high forage diet where grass silage and hay accounted for 75 percent of the dry matter intake. The wheat bran and sugar beet pulp diet did not have an effect on milk production, milk composition, feed intake, or total chewing activity. The researchers concluded that wheat bran and sugar beet pulp could replace some common cereal grains in mid-lactation dairy cows without hindering performance. Even though this high forage level ration is not typical in the U.S., it does illustrate that utilizing by-product feeds in the ration can improve sustainability, stretch available forage supplies, or serve as a substitute for corn or soybean meal.
Preparation of Grains and Feeds
Cereal grains need to be adequately prepared or broken to increase the digestibility of the grain and the entire ration. Preparation needs to be equivalent to grinding through a 1/2 to 5/8-inch screen. Cracked poultry corn is not fine enough for good digestibility in lactating cow diets. Steamed, crimped, steam rolled, or steam flaked grains are approximately equal to ground grains in digestibility. Heat-processed grains should be limited, however, to 35 to 40 percent of the concentrate mix to avoid ruminal acidosis and the subsequent milk fat yield decrease associated with it. This guideline will depend on if the grain is fed in a TMR compared to conventionally fed (forages and grains fed separately). Mechanically crimped, rolled, or flaked grains without heat are approximately equal to ground material if comparable particle size is attained. A roller mill must have more crimps to the inch to properly prepare small grains than the number for corn.
There are some additional guidelines to consider when feeding grains in a dairy herd. Coarse or special textured feeds preferably should furnish only part of the concentrate when used as a top-feed for high-producing cows (greater than 80 pounds of milk). If a textured grain is fed to the entire herd, limit the amount to 15 to 25 percent of the formula. These limitations may change depending on the total starch level that is formulated and if the herd is fed a TMR versus conventionally.
Heifers under four to six months of age can handle whole or more coarsely prepared grains since they can chew them adequately. Preparation may be necessary in some mixtures to prevent sorting and improve digestibility.
Ingredients in a pellet generally must be finely ground (3/32-inch screen or finer) to enable efficient pelleting. By using heat, moisture and pressure, the meal type feed is forced through holes in a metal die forming the pellet. It is recommended that high-starch ingredients be limited to 35 to 40 percent of the concentrate mix to avoid negative effects on animal health and performance (e.g., milk fat depression). Inclusion of sufficient fibrous ingredients in a pellet formula is required to provide sufficient hardness and reduce fines. For example, 15 percent wheat midds and 10 to 15 percent of a mid-protein ingredient such as corn gluten feed, brewers, or distillers' grain would make a hard pellet. Adding a binding agent to hold pellets together is another option.
Proper preparation of high moisture grains is necessary to prevent sorting of ear corn during ensiling (cobs and grain), to increase digestibility of the grain and the entire ration, and to minimize sorting during feeding. Ensiled grains may be prepared more coarsely than dried grains. Starch in high moisture grains is more soluble and degrades more quickly in the rumen than starches in dry grains. This can be offset by somewhat coarser preparation.
Roller mill specifications for high-moisture grains
|Shelled corn||6.5 to 7||200+|
|Small grain||8 to 10||400|
Most grains must be broken into several pieces when rubbed between the fingers or in the palm of the hand. Cob particles must be fine enough to prevent sorting.
Appropriate Uses of Feed Ingredients
Numerous cereal grains, protein sources, and by-product concentrate ingredients are used to supplement a forage ration. Using these ingredients can help meet the cow's requirements for energy, protein, minerals, and fiber (Table 1). Tables 2a and 2b provide the key nutrients of commonly used concentrate ingredients. Table 3 lists bushel weights and conversion factors that can be used in pricing. Table 4 lists the differences in extent of ruminal digestion of starches as affected by source and processing. The following is a list of commonly used concentrates and how they complement a diet.
Ingredients high in crude protein
(> 35% crude protein on a dry matter basis):
Animal protein blend
Corn gluten meal
Meat and bone meal
Soybeans, raw and roasted
Ingredients high in undegradable intake protein
(>60% of crude protein on a dry matter basis)
Animal protein blends
Corn gluten meal
Soybeans (properly roasted)
Ingredients high in degradable intake protein
(>50% of crude protein on a dry matter basis)
Corn gluten feed
Ingredients high in soluble protein
(>40% of crude protein on a dry matter basis)
Corn gluten feed
Ingredients high in starch
(>40% on a dry matter basis)
Ingredients high in fat
(>15% on a dry matter basis)
Soybeans, raw and roasted
Ingredients high in neutral detergent fiber
(>34% on a dry matter basis)
Corn gluten feed
Ingredients high in sugar
(>19% on a dry matter basis)
Table 1. Suggested maximum intakes for lactating dairy cattle on various concentrate ingredientsa
|Item||Finished concentrate (% air-dried)||Total ration dry matterb (% ingredient dry matter)|
|Animal protein blends||4.5||3|
|Apple pomace w/no hulls, chips||20 (cows)||10|
|Apple pomace w/no hulls, chips||50 (heifers)||10|
|Barleyc||0, 35p||0, 14p|
|Beet pulp||25, 40p||10, 16p|
|Beans, peas||15, 20p||6, 8p|
|Bread, bakery product||20||10|
|Brewers grains, wet||45||22|
|Cornc||0, 35p||0, 14p|
|Corn screenings||0, 35p||0, 14p|
|Corn gluten feed||20, 30p||8|
|Corn gluten meal||12, 12p||6, 6p|
|Citrus pulp||25, 40p||10, 16p|
|Distillers grains, dry||25, 35p||10, 14p|
|Distillers grains, wet||35||17|
|Hominy||40, 35p||16, 14p|
|Milo, sorghum||30, 40p||15, 20p|
|Oatsc||0, 40p||0, 16p|
|Ryec||10, 15p||4, 6p|
|Spelt||20, 35p||8, 14p|
|Starch, as ingredient||25||12|
|Triticale||20, 35p||8, 14p|
|Urea: concentrate mix||1.5||0.60|
|Wheatc||20, 35p||8, 14p|
|Wheat bran||25, 35p||12, 15p|
|Wheat midds||15, 20p||7, 10p|
|Total mineral ingredients||5, 6p||2.5, 3p|
|Total starchy ingredients||0, 35p||0, 14p|
aWhen two maximums are listed, the first refers to a meal-type finished feed, and the second (p) is for use in a pelleted feed or as a heat-processed ingredient.
bRefers to a percentage of ingredient dry matter as a percentage of total ration dry matter (TRDM).
cThe "0" given for some ingredients indicates that there is no maximum for use in a meal or non-heat-treated form. Heat-treatment via pelleting, steam rolling, steam crimping, extrusion, steam flaking, or roasting may depress milk fat test by 0.1 to 0.3 percent.
dDo not use in rations for calves under four to six months old.
Table 2a. Concentrate ingredients and their expected analysis for the major nutrients.
% of CP
% of CP
|Animal protein blend||91.9||75.7||28.9||26.8||13.3||6.1||13||2.0||0.89|
|Brewers grain, wet||23.7||28.7||36.2||12.6||49.3||5.6||9.8||3.3||0.82|
|Candy by-product||89.3||12.9||no test||34.9||24.6||15.8||12.6||19.5||0.98|
|Corn gluten feed||89.5||23.6||62.7||51.0||36.2||14.5||4.3||4.0||0.78|
|Corn gluten meal||91||67.1||17.7||13.1||9.7||15.1||3||2.6||0.91|
|Corn snaplage, wet||58.4||8.2||58.8||46.6||23.3||57.2||3.5||1.6||0.9|
|Corn, steam flaked||85.9||8.2||30.0||12.8||9.1||71.8||3.4||2.5||0.93|
|Meat and bone meal||95.1||60.4||no test||no test||28.1||2.6||13.4||no test||0.78|
aDM=dry matter; CP=crude protein; DIP=degradable intake protein; SP=soluble protein; NDF=neutral detergent fiber; ESC=ethanol soluble carbohydrates (simple sugars).
Table 2b. Concentrate ingredients and their expected analysis for the major minerals.
|Animal protein blend||91.9||2.92||1.6||0.14||0.73||0.63||0.69||0.9|
|Brewers grain, wet||23.7||0.34||0.69||0.23||0.15||0.33||0.03||0.25|
|Corn gluten feed||89.5||0.08||1.08||0.43||1.48||0.5||0.27||0.3|
|Corn gluten meal||91||0.06||0.57||0.09||0.28||0.88||0.08||0.11|
|Corn snaplage, wet||58.4||0.06||0.27||0.12||0.52||0.1||0.01||0.14|
|Corn, steam flaked||85.9||0.03||0.24||0.09||0.33||0.1||0.01||0.08|
|Meat and bone meal||95.1||7.80||3.92||0.19||0.58||0.56||0.64||0.49|
aCa=calcium; P=phosphorus; Mg=magnesium; K=potassium; S=sulfur; Na=sodium; Cl=chloride.
Table 3. Approximate volume weights for selected feedstuffs.
|Feed||Pounds/bushel||Bushel/hundred weighta||Pounds/cubic feetb|
|Brewer's grain Dry||19||5.26||15|
|Brewer's grain Wet||44||2.27||35|
|Corn, ear Whole|
|Corn, ear Whole|
|Dairy feed, 16% crude protein|
|Dairy feed, 16% crude protein|
|Dairy feed, 16% crude protein|
|Distillers corn grain, dry||19||5.26||15|
|Green chop forage||20||5.00||16|
|Corn silaged(after removal)||20-30||3.30-5.00||16-24|
|High moisture ear corn (after removal)||30-35||2.90-3.30||24-28|
|Haylage (after removal)||15-30||3.30-6.70||12-24|
|Total mixed ration||28||3.57||35|
aThe bu/cwt values given in the column may be used as factors to convert bushel prices to hundredweight prices or vice versa. Example: Whole shelled corn is $5.00/bu. so $5.00 x 1.79 = $8.95/cwt. Shelled corn at $8.95/cwt/1.79 = $5.00/bu.
bOne standard bushel = 1.25 cubic feet; one standard cubic foot = 0.8 bushels.
cThe standard weight of 70 pounds is usually recognized as being about 2 measured bushels of corn, husked, on the ear because 70 pounds would normally yield 1 bushel or 56 pounds of shelled corn. One bushel of ear corn = 2.5 cu ft; 1 cu ft = 0.4 bushels of ear corn.
dOne comfortably rounded silage forkful (six-tine) holds about 0.5 bushels.
Table 4. Differences in extent of ruminal digestion of starches as affected by source and processing
(Percentage digestion in the rumen)
|Ensiled, high moisture, fine grind||99||99||98||85||--|
|Steam flaked, thin flake||99||98||97||86||84|
|Ensiled, high moisture, coarse rolled||--||--||--||82||80|
|Dry, fine grind||94||93||91||78||72|
|Dry, medium grind||89||88||87||74||68|
|Dry, coarse grind||79||78||77||65||61|
Source: Van Horn et al., Large Dairy Herd Management, IL. 1992.Source : psu.edu