Feeding Systems of Farm Animals
The different types of feed and their characteristics
A successful dairy feeding system is defined as one that delivers the needed nutrients to each cow at the correct time (stage of lactation) to maintain maximum milk production. No one system is correct for all dairy producers. The feeding system selected must consider delivery of forages, grain, protein and minerals, either individually or in various combinations.
Forages are the primary source of fibre required by the cow to maintain rumen digestion and function as well as to stimulate rumen microbial growth, rumination, and saliva production. Forages are classified as feeds high in fibre and low in digestible nutrients and include whole plants of maize, small grains (such as oats, barley, or wheat), legumes, and grasses. Forages are usually a more economical source of nutrients than grains, protein supplements, or mineral-vitamin premixes.
Forage selection depends largely on agronomic considerations (such as soil types, climate, yields, and nutrient yield per acre). Forage quality must be the primary consideration regardless of forage type. High-quality forage will be consumed in larger amounts and is more digestible than mature, lower-quality forages. The addition of grain to diets cannot completely compensate for lowered animal performance from low-quality forages.
Forages are divided into groups with high, medium and low protein content.
- Legumes (high protein) tropical
- Grasses (medium protein)
- Crop residues (low protein)
Lucerne, desmodium (green leaf & silver leaf), siratro, calliandra, leucaena, mulberry, vetch, sesbania, sweet potato vines, soya beans, green grams
Napier grass, Guatemala grass, giant setaria, guinea grass, Rhodes grass, Kikuyu grass, Congo signal, Sudan grass, cow candy, oats
Maize Stover stripped maize cobs, sorghum Stover, banana stems, wheat straw, rice straw, and barley straw.
- Average 16 – 28 %
- Average 6 – 12 %
- Below 6 %
Pastures can provide significant quantities of high-quality forages to dairy cows and heifers if managed intensively. Potential benefits of a pasture-based forage system for dairy herds include:
- Increased yield and quality of forage from land that previously was unproductive
- Decreased equipment and fuel for harvesting forages
- Less manure handling and lower bedding costs
- Reduced weather-related risks in harvesting forages
- Potential for better animal health because of increased exercise.
- Limitations to pasture-based forage systems are:
- Maintenance of high yields and quality of forages during the entire growing season
- Correct supplementation to maximize productivity and profitability from pasture forages and the short length of the grazing season in some areas.
These comprise species such as Legumes (Lucerne & desmodium) 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% of their body weight in forage DM. High-quality forages fed in balanced rations will supply much of the protein and energy needed for milk production.
Important considerations in harvesting Lucerne and grasses are cutting date and stage of maturity. With increasing maturity, plants decrease in protein, energy, calcium, phosphorus, and digestible DM, while increasing in fibre. As a fibre, 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 or hay. Silage and hay offer the advantages of less leaf loss, less time for field curing, and, usually, reduced labour in harvesting. Legume-grass silage should be put up at 35 to 40% DM in a bunker silo, hay at 40 to 50% DM in a stave silo, and 50 to 60% 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 mould or heat excessively. Legume or grass silages should be chopped (3/8-inch theoretical length of chop) and at proper moisture for ensiling. Rapid filling, good packing, and sealing are key to good preservation. Hay should not be baled or stacked until the DM content is at least 80%. Otherwise, heating and moulding can develop.
Legumes and wet grass hay can heat excessively and lose feeding value. A brownish, caramelized appearance indicates prolonged and excessive heating. It causes the protein to join with carbohydrates, 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 storage structure, can be avoided or reduced by keeping silos in good repair and harvesting, ensiling, and storing the crop using good management practices.
Guidelines in the selection of forage grass or legume species
Good legume or grass should be:
- Fast-growing and well-adapted to frequent cutting or defoliation
- Adapted to climatic and soil conditions where they are to be planted
- Able to provide good soil cover and prevent weeds from growing
- Pleasant/ edible by the livestock
- Have a high nutritive value containing high levels of energy and protein and no poisonous substances.
- Easy to conserve as hay or silage or ability to stay green on the farm during harsh weather
- Able to produce good quality seed / vegetative planting material in adequate quantities.
- Ability to intercrop with other crops if intercropping is desired.
- Tolerance to diseases and pests
- Fast growth to produce adequate forage material.
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 must be 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 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 the DM intake of animals and evaluating storage problems. Forages put in silage too wet reduce intake and have butyric acid fermentation. Putting in silage 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 forage, 12% or less of the total CP is unavailable. If no heat damage or protein loss to the animal has occurred, Crude Protein and Adjusted Crude Protein are equal. Acid detergent fibre is highly related to digestibility. As ADF increases, digestible DM (DDM) or TDN and energy content of forages decline.
Two basic systems for feeding minerals are:
Force-feeding systems where the minerals are mixed with grain and/or forage, fed in a total mixed ration, or top dressed.
Free-choice systems where cows have unrestricted access to various mineral mixtures. Cafeteria-style mineral feeders are an example. Most dairy cattle are unable to balance their mineral requirements through free-choice feeding alone. Therefore, a cow’s mineral requirement, including salt, should be met through force-feeding in the ration, with supplementary calcium-phosphorus minerals and salt offered free-choice. Mineral sources should be evaluated on the cost per unit of mineral and the quality of the mineral source.
Total Mixed Rations
Total mixed rations (TMR), or complete rations, are those with all the forage and grain ingredients blended together, formulated to specific nutrient concentrations, and fed free-choice. The main advantages of TMR feeding are:
- Cows consume the desired proportion of forages when two or more forages are offered.
- Cows consume the desired amount of forage relative to the amount of grain offered.
- There is less risk of digestive upsets.
- Feed efficiency improves. It allows for greater use of unpalatable feeds, NPN sources, and commodity feeds.
- There is potential to reduce the labour required for feeding.
- It allows for greater accuracy in formulating and feeding.
The potential disadvantages include the following:
- It requires a significant equipment investment in a mixer.
- It creates a need to group cows into two or more groups.
- Rations must be carefully formulated and continually checked.
- Pasture feeding and large amounts of long hay are difficult to incorporate into rations.
The objective in formulating rations is to provide animals with a consumable quantity of feed stuff that will supply all required nutrients in adequate or greater amounts and do so in a cost-effective way. The four most common ways of expressing ration information are:
The amount of each feed fed, along with its nutrient composition, must be known to obtain an accurate ration analysis. A ration analysis summarises all feeds in the ration and the nutrients they contribute. An analysis does not balance the ration, and therefore does not correct any nutrient deficiencies or excesses.
A ration balancer program combines feeds to meet the nutrient specifications set for a ration. The amount of each feed to be included in the ration will be determined based on its nutrient contributions and how it fits with other feeds in meeting nutrient specifications. A balancer program does not consider feed costs or profit.
A normal least-cost formulation involves specifying the nutrient requirements or constraints for the ration and finding the combination of feeds that meet or exceed these constraints at the lowest cost per kg of DM. The least cost formulations change as feed costs change. An opportunity or break-even cost for feeds not used in the ration will often be given. When the price of a new feed goes below the opportunity price, it is considered a good buy, and the ration should be reformulated to see how much of that feed can now be used in the ration.
A true maximum profit ration program includes the least cost function, incorporates milk price information, and uses a maximum profit (income over feed cost) as one of the constraints or specifications to formulate on. The difference between maximum profit and least cost or balanced rations is that the computer selects feeds and a milk production level to obtain a maximum profit; whereas, in the least cost or balanced rations, the computer selects only feeds to meet the nutrient requirements specified for a given level of milk production.
Ration Formulation Thumb Rules—Lactating Cows
Dry Matter Intake needs to be known.
The Forage DM minimum is 40% of the total DM intake or approximately 1.5% of body weight. Maximum grain DM is 60% of total DMI, or not more than 2% of body weight. Between 4.5 and 32 litres of milk per day, feed grain at ½ kg per 1.5 litres of milk, and above 32 litres of milk, feed grain at ½ kg per 1.6 litres of milk. The minimum recommended acid detergent fibre (ADF) in ration DM is 18%, with 19 to 20% preferable, especially when fat is present.
Neutral detergent fibre (NDF) should be at least 28% of the ration DM. Forages should account for 75% or more of the total ration NDF (1.2% of body weight or 21% of ration DM).
Protein needs to meet requirements (17 to 19% in early lactation rations). A low rumen degradable protein source may be beneficial in early lactation rations for high-producing cows. Limit urea to 200 grams per cow per day and preferably to not over 200 grams per day in phases 1 and 2. The maximum total fat in rations is 7% of the DM. A guideline is no more than 2% added fat from any of three sources, animal, vegetable or rumen inert. Increase calcium to 0.9 to 1%, magnesium to 0.3%, and ADF to 20% or more in the ration DM when feeding fat.
Salt should be included in the grain mix at 1% or fed at the daily individual cow rate of 28 grams for maintenance plus 28 grams for every 14 kgs of milk.
A calcium-phosphorus mineral source should be included in the grain mix at 1 to 2% or fed at an approximate rate of 28 grams per 4.5 kgs of milk. Supplement vitamins (A, D, and E) and trace minerals in the ration to meet requirements.
The rumen microorganisms manufacture all of the B vitamins and vitamin K. Vitamin synthesis in the rumen is sufficient for growth and maintenance. Under most conditions, cattle with functioning rumens do not require supplemental B vitamins or vitamin K in the diet. Niacin (B3) and thiamine (B1) may be needed under stress conditions.
Most of the digestion and absorption of fat occurs in the small intestine. Rumen microorganisms change unsaturated fatty acids to saturated acids through the addition of hydrogen molecules. Thus, more saturated fat is absorbed by cows than by simple-stomach animals. Feeding large quantities of unsaturated fatty acids can be toxic to rumen bacteria, depress fiber digestion, and lower rumen pH.
Feedstuffs are often classified as forages and concentrates. Concentrates usually mean high-quality; low-fibre feeds and include cereal grains, milling by-products, protein sources, and fats. Concentrates have 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% 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 Lucerne with 24% ADF and 36% NDF is classified as forage.
Maize silage: Good maize silage contains nearly 50% 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. Maize silage requires protein and mineral supplementation to be balanced for high milk production. To attain maximum yield, maize should be harvested for silage when it has reached physiological maturity: kernels are fully dented, the 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% (the corn ear is 55 to 60% DM when the whole plant is 32 to 38% DM). Immature maize silage is usually wetter, below 32% DM, and yields less total dry feed per acre. Seepage losses from the silo occur when material below 32% DM is put in silage. If maize becomes too dry before ensiling, field losses are greater, and the feed may not ensile as well (poor compaction, moulding, 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 maize except during drought conditions. Energy and intake potential is lower than with corn silage.
Small grains: Oats, barley, wheat, and rye can be harvested as forage, although yield per acre is usually less than maize, legume, or grass forages. Harvest in the boot stage for the highest quality. Delaying harvest until the 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% 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 the additional fibre is needed. Some straws can be used for dry cows and older heifers if adequately supplemented.
Stover: Maize 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 are 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 labour. Large herds are not handled easily in pasture situations. Additional grain is needed for high-producing cows. As the quantity and quality of pasture change during the dry months, cattle need to be supplemented with stored forages and other feeds.
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.
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, cracking or grinding) increases its digestibility when fed to cows. As much as 30% 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 per cent and cause rumen acidosis. Pelleted grain is not dusty and may increase palatability and intake, but it 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.
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% of the grain ration.
Beet tubers can be obtained either in plain form from the field or as molasses beet pulp. It is relatively high in energy, adds highly digestible fibre and bulk to diets, and enhances palatability. The maximum feeding rate is 30% of the ration DM.
Cottonseed, whole or crushed, is a medium protein, high fat, high fibre, and high energy feed. The whole cottonseed is white and fibrous, while the de-linted cottonseed is black and smooth in appearance. The amount fed should not exceed 3 kg per cow per day.
Maize, ear or maize and cob meal is a relatively high-energy feed liked by cows. It contains 10% less energy than shelled maize. The fibre supplied by the cob aids in maintaining fat tests and keeping cows on feed.
Maize, 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 maize can be grown successfully, it is generally an economical energy source. 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.
Maize, 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 labour of grain processing or grinding is reduced.
High-moisture ear maize should be stored from 28 to 32% moisture and processed before storage. The wet cob is more digestible than the cob in dry maize.
High moisture-shelled maize should be stored with 25 to 30% moisture content. In airtight silos, the shelled maize can be stored whole or ground and rolled upon removal from the silo. In typical 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 maize for dairy cattle.
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 the fatty acid (saturated or unsaturated) composition of the fat. Total added fat in diets should not exceed 4% (DM basis), with animal, vegetable or rumen-inert fats individually not exceeding 2%.
Molasses (cane) supply energy and is used primarily to enhance the acceptability of the ration. The amount used should be limited to 5 to 7% of the grain mix (10% in pelleted feeds) to avoid undesirable rumen effects.
Oats contain 15% less energy but 20 to 30% more protein than shelled maize. The advantage of adding oats to dairy rations is that it adds fibre and bulk, and may help maintain rumen function.
Sorghum grain can be used to replace maize in diets. The energy content is about 90% of that of maize, and the protein content is variable (7 to 12% CP). Sorghum must be ground before feeding to prevent whole seed passage, but grinding lowers palatability because of dustiness.
Soya bean hulls are good sources of highly digestible fibre and may replace starch in the diet, but they do not forage fibre. Limit amounts to 33% of the grain ration.
Wheat is not used often because the price is usually too high. It is acceptable in dairy cattle rations in reasonable amounts (less than 50% 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 fibre to the diet. It is relatively high in protein and phosphorus, improves ration palatability, and functions as a laxative.
Find more information in the Books of the Author: Success in Agribusiness
Feeding Systems of Farm Animals