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Table 1, Minimum nutrient requirements of horses, provides a guideline as to how these requirements change among mature horses of four different sizes. The crude protein is expressed in pounds per day; calcium and phosphorus are expressed in grams per day; digestible energy needed per day is expressed in Mcal's per day. Vitamin A is measured and expressed as 1000 International Units (I.U.). Exercise at a moderate level of some trotting and cantering for one hour each day was used.
Mature Digest Crude Calcium Phosphorus Vit A body energy protein 1,000 weight lbs. M.cal/ lbs./ % grams/ % grams/ % IU's/ ___ day day of day of day of day diet diet diet ----------------------------------------------------------------------------- Mature horse 440 7.4 .65 8 8 .25 6 .20 6.0 at rest 880 13.4 1.18 8 16 .25 11 .20 12.0 (maintenance) 1100 16.4 1.45 8 20 .25 14 .20 15.0 1980 24.1 2.13 8 36 .25 25 .20 27.0 Mature horse 440 11.1 .98 10 14 .30 10 .25 9.0 at moderate 880 20.1 1.77 10 25 .30 17 .25 18.0 work** 1100 24.6 2.17 10 30 .30 21 .25 22.0 1980 36.2 3.20 10 44 .30 32 .25 40.0 Mares, last 440 8.9 .86 11 17 .50 13 .40 12.0 30 days of 880 16.1 1.56 11 31 .50 23 .40 24.0 pregnancy 1100 19.7 1.91 11 37 .50 28 .40 30.0 1980 29.0 2.81 11 55 .50 42 .40 54.0 Mares, peak 440 13.7 1.52 13 27 .50 18 .35 12.0 of lactation*** 880 22.9 2.52 13 45 .50 29 .35 24.0 3 months 1100 28.3 3.15 13 56 .50 36 .35 30.0 1980 45.5 5.67 13 101 .50 65 .35 54.0 ----------------------------------------------------------------------------- * From Nutrient Requirements of Horses, 1989, National Research Council. ** Examples are horses used in ranch work, roping, cutting, barrel racing, jumping, etc. ***Lactation level is assumed to be 3% of body weight/day. -----------------------------------------------------------------------------Protein is needed by the horse for growth, muscle development, reproduction, lactation, repair of body tissues, and skin and hair development. If energy in the diet is low, protein can also be converted to energy. It is necessary to consider the quality of the protein (the content of essential amino acids) as well as the total amount of protein fed. The lysine (an indispensable amino acid) requirement for weanlings is .6-.7% of the diet and for yearlings .5% of the diet.
No other amino acid requirements have been determined. Horsemen must rely on legume hay or quality concentrate feeds to provide the balance of amino acids needed. Commercial feeds containing urea, a non-protein nitrogen source, should not be fed to horses because the horse is unable to utilize non-protein nitrogen to the degree that cattle can. Feeding excessive protein to horses with the belief that it will increase muscle development is not valid and is very expensive. Excess protein (that fed above the requirement) is broken down into energy (calories) and a nitrogen by-product called urea, which is excreted in the urine causing the horse to urinate and drink more.
Vitamins play a variety of roles in the body, and quite often they are catalysts for metabolism. While only a minute amount of each may be needed, a deficiency can cause severe side effects or illness once the reserves are depleted. Vitamins are classified into two groups. The fat-soluble vitamins, which can be stored in the body for future use, are A, D, E, and K. Because they are stored, toxicities can occur if fed in excess. The water-soluble vitamins, which are not stored and must be supplied continually are the B-complex vitamins. Many vitamin supplements are available, but should only be used after determining that the horse's diet needs to be supplemented. Never supplement vitamins in amounts which greatly exceed the daily requirements. Be especially conscious of levels of the fat-soluble vitamins being fed. In general, a good, balanced diet of green hay, grain, and sunlight will provide adequate amounts of vitamins for the horse unless under a large degree of stress.
Mineral content of a horse's diet is determined by the soil and water in the area, the quality of feed, and the proportion of grain to hay in the diet. The main minerals are often classified as macro minerals. These are Calcium (Ca), Phosphorus (P), Sodium (Na), and Chlorine (Cl). Depending on the area, trace minerals of concern are Iodine (I) Iron (Fe), Selenium (Se), Zinc (Zn), Manganese (Mn), and Copper (Cu). These trace or micro-minerals are also referred to as electrolytes.
Cur Cur Expt'd D.E. Crude Protein Calcium Phosp Vit A age body daily M.Cal/ lbs/ (%) grams/ (%) gram/ (%) 1,000 (Mo.) weight gain day day day day IU's/ day --------------------------------------------------------------------------------- Growing horses ** 440 lb mature weight 4 165 .88 7.3 .81 16 16 .70 9 .50 3 12 308 .44 8.7 .86 14 12 .55 7 .40 6 18NT*** 374 .22 8.3 .83 13 10 .45 6 .35 8 24T**** 407 .11 11.4 1.07 12 13 .45 7 .35 8 Growing horses 880 lb mature weight 4 319 1.87 13.5 1.49 16 33 .70 18 .50 7 12 583 .88 15.6 1.55 14 23 .55 13 .40 12 18NT 726 .55 15.9 1.58 13 21 .45 12 .35 15 24T 803 .33 21.5 2.02 12 27 .45 15 .35 16 Growing horses 1100 lb mature weight 4 385 2.00 14.4 1.59 16 34 .70 19 .50 8 12 715 1.10 18.9 1.88 14 29 .55 16 .40 15 18NT 880 .77 19.8 1.97 13 27 .45 15 .35 18 24NT 990 .44 26.3 2.47 12 34 .45 19 .35 20 Growing horses 1980 lb mature weight 4 605 2.86 23.1 2.55 16 53 .70 29 .50 12 12 1100 1.98 31.2 3.10 14 49 .55 27 .40 22 18NT 1463 1.54 33.6 3.34 13 49 .45 27 .35 30 24T 1672 .99 42.2 3.96 12 61 .45 34 .35 34 ------------------------------------------------------------------------------- * From Nutrient Requirements of Horses, 1989 National Research Council. ** Moderate rate of gain. *** Long yearling (18 month) not in training. **** Two year old (24 mo) in training. -------------------------------------------------------------------------------Table 2 shows the requirements for growing horses of four different mature sizes. The 18 month old, long yearling example is not in training, and the 24 month old is in training. The daily gain expected indicates the growth rate expected. The growth rates used are moderate. There is plenty of research to associate faster growth rates with bone disorders.
Salt (NaCl) aids the body in fluid and temperature regulation. In hot weather, the temperature of the body is controlled by sweating. Water, salt, and other minerals are given off and need to be replenished. The salt intake of a horse is directly proportional to the water intake. It is vital to have salt available for horses either as a block, loose, or mixed in the feed. This is best done in the form of iodized salt or trace-mineralized salt. Allow free access to loose or block trace mineralized salt with selenium as horses will consume the amount they need as long as they have access to plenty of water. All horses require about 1 ounce of salt daily that provides at least .1 ppm of selenium in the total ration. Improper dietary levels of these trace minerals, especially Cu, Zn, Fe, and Mn are thought to contribute to developmental orthopedic diseases such as osteochondrosis desecans (OCD), physitis, and contracted tendons.
The amount of Calcium and Phosphorus, and the ratio between these two elements are vital to bone development and maintenance. The ideal calcium to phosphorus ratio is 1.5:1.0. The ratio of Ca to P in the diet should be between 1:1 and 3:1 for all horses. Adult horses can tolerate a ratio up to 6:1 before problems occur, but growing animals have trouble on Ca:P ratios above 3:1. A supplement with more phosphorus than calcium should be used when feeding good legume hay and no grain. With a deficiency of calcium or an imbalance of the two elements, the horse's bones will become soft and weak or simply won't develop properly.
--------Adequate levels---------- Maintenance Growth and Working Maximum broodmares tolerance levels ------------------------------------------------------------------------------- Minerals Sodium, % .10 .10 .30 3.% Chloride .3 .40 .40 5.% Magnesium .10 .1 .15 .5 Sulfur,% .15 .15 .15 1.25% Iron ppm** 40 50 40 1000 Zinc ppm 40 40 40 500 Manganese ppm 40 40 40 1000 Copper ppm 10 10 10 800 Iodine ppm .1 .1 .1 5.0 Cobalt ppm .1 .1 .1 10 Selenium .1 .1 .1 2.0 Flourine ppm -- -- -- 50 Vitamins Vitamin A IU/lb 910 1667 910 7273 Vitamin D IU/lb 135 135 365 1000 Vitamin E IU/lb 25 37 37 450 Thiamine ppm 3 3 5 3000 Riboflavin ppm 2 2 2 -- ------------------------------------------------------------------------------- * NRC, Nutrient Requirements of Horses, #6, 5th Ed., 1989 ** Parts per million (ppm) = mg/kg = mg/2.2 lb -------------------------------------------------------------------------------
A maintenance ration is that on which a mature idle horse will maintain normal weight, or condition score under average climate conditions while doing nothing. It should be remembered that extreme cold climatic temperatures (less than 20 degree F) cause the horse to use energy to control body temperature. Work causes the energy requirement to increase. As the intensity or duration of the work increases from light to moderate to intense, the requirements for energy increase 25%, 50%, and 100% above maintenance, respectively.
Lactation and growth increase demands for protein, minerals, and vitamin A as well as energy. With any sort of activity, especially lactation, the Ca and P needs are increased. There is a critical need for increases in protein, minerals, and vitamin A during the last three months of gestation. Energy requirements during the ninth, tenth, and eleventh months of gestation increase 11%, 13%, and 20% respectively. A young foal, while nursing the dam, is drinking about 22% protein, 16% fat, and 58% carbohydrates. It is necessary to keep young foals on a high-protein and high-energy diet. As they get older their need for high protein will decrease.
A horse being maintained can meet its requirements on good pasture or hay only; however, as more is expected from a horse, its nutrient requirements increase.
Most horses will eat about 2.5 pounds of air-dried feed per 100 pounds of body weight per day. This depends on the feedstuff's quality and dry matter composition, but a 400 lb. horse eats about 10 lbs. of feed per day, and a 2000 lb. horse eats about 50 lbs. of feed per day. To maintain normal digestive processes in the large intestine and to avoid boredom, all horses should receive at least 1 pound of forage per day per 100 pounds of body weight. This can be supplied by pasture, long hay, or cubes with at least a three quarter-inch particle size. The pelleted products can cause digestive problems when fed alone. In addition, a diet consisting solely of pellets results in less time spent eating and can lead to boredom and increased wood chewing.
Dry** D.E.** C.P.** Ca** P** Vit.A** Matter% MCal/lb lb/lb g/lb g/lb 1000IU/lb ------------------------------------------------------------------------------- Hay Alfalfa, early bloom 90.5 1.02 .18 5.81 .86 23.00 Full bloom 90.9 .89 .155 4.90 .99 10.74 Clover, red 88.4 .89 .132 5.53 .99 9.88 Orchardgrass Early bloom 89.1 .88 .114 1.09 1.36 6.08 Late bloom 90.6 .78 .076 1.09 1.22 3.29 Bromegrass Mid-bloom 87.6 .85 1.26 1.13 1.13 2.45 Timothy Early bloom 89.1 .83 .096 2.04 1.13 8.51 Late bloom 88.3 .72 .069 1.54 .59 7.23 Fescue Full bloom 91.9 .86 .1181 .81 1.32 8.73 Mixed 30% legume 89.0 .93 .1332 .66 1.10 11.72 Concentrates Barley 88.6 1.49 .117 .23 1.54 .37 Corn 88.0 1.54 .091 .23 1.27 .98 Oats 89.2 1.30 .118 .36 1.54 .02 Wheats. red 88.4 1.55 .114 .14 1.77 __ Wheat bran 89.1 1.33 .154 .59 5.13 .48 Soybean meal 89.1 1.43 .445 1.59 2.86 __ Linseed meal 90.2 1.25 .346 1.77 3.63 __ Molasses (blackstrap) 74.3 1.18 .043 3.36 .36 __ Vegetable oil 99.8 4.08 __ __ __ __ Mineral Supplements Limestone, CaC03 100 __ __ 178.67 .18 __ Oystershell 99 __ __ 170.64 .31 __ Bone meal, steamed 97 __ __ 135.12 56.58 __ Rock phosphate, defl. 100 __ __ 145.15 81.65 __ Dicalcium phosphate 97 __ __ 96.81 83.73 __ Sodium triphosphate 96 __ __ __ 108.86 __ ------------------------------------------------------------------------------- * Derived from nutrient requirements of Horses 5th Ed. N.R.C. 1989. ** All nutrients are expressed on an as fed basis. -------------------------------------------------------------------------------Hays vary greatly in quality. Quality depends on the maturity of the plant when harvested, extent of mechanical damage, and the method used in drying. Legume hays (alfalfa, lespedeza, birdsfoot trefoil, and clover) provide higher levels of protein, calcium, and vitamin A (carotene) than do grasses. Grass hays (timothy, orchardgrass, fescue, and smooth bromegrass) are lower in calcium and protein and higher in fiber than legumes. Where both legumes and grasses are available, a mixed hay is an ideal forage for horses. Table 4 on the previous page shows that as the plant matures, it becomes less nutritious and looses digestibility. All hay is best harvested before one-half of the plants have headed out or bloomed. Pure legume hays should be fed to growing foals and lactating mares, because of their very high calcium and protein requirements. Pure alfalfa may be too rich in energy and protein for performance, and has more calcium than is needed for pregnant mares. Table 4 gives the composition of various common horse feeds. Energy content is expressed in Mcal's per lb. and protein, Ca and P are expressed as amount of nutrient per pound of feedstuff.
As more performance (work) or growth is expected of an animal, a proportionately larger amount of concentrates must be fed. Generally, most of the energy, phosphorus and some of the protein must come from the concentrate. Oats are a popular grain for horses because they are palatable and have a high protein and fiber level. Corn is another popular grain to use in horse rations. It is high in energy but low in both the quantity and quality of protein. Corn is often referred to as a heavy grain because it is denser and higher in energy per unit weight than oats. Corn is usually the most economical energy source.
Grains (and all other feeds) should be fed by weight rather than by volume. The nutrients are expressed "per pound," thus, it is necessary to know how many pounds are being fed. It is beneficial to crack, roll, or crimp grains to break the outer shell thereby allowing more efficient digestion and use of the grain. But this is not inexpensive and often it is more economical to feed 5 to 6% more whole grain. Processed grains are dustier and don't store as well for extended times as whole grains. Bran has traditionally been added to horse diets to serve as a fiber source and a laxative. It can serve as a good source of energy and protein, but usually it is added at very low levels and the fiber content is negligible compared to hay. It would be more economical to feed corn and soybean meal than bran.
Other concentrates are commonly added to horse rations to increase protein level. Soybean oil meal and linseed oil meal are two of the most common sources. When compared to soybean, linseed oil meal does not have as good a quality protein as it is lower in lysine. There are many excellent commercial feeds that are already balanced specifically for horses. Usually these have the vitamins and minerals added; but to be safe, check the bag content label or ask the dealer for a composition profile. Most horseowners should rely on the expertise of commercial feed companies and purchase concentrates designed for the specific category of horse. Often the convenience and quality is well worth any cost increase. It is wise to blend needed vitamins, minerals, or protein supplements into the concentrate mixture, thereby knowing exactly what the horse is getting each day.
The nutrient composition is vital but no more so than the way the ration is delivered. Use as much good forage as possible; feed clean, dust- and mold-free feedstuffs that are free of any toxic weeds.
It should be emphasized that the effects of a ration should be closely observed for at least two weeks to determine any changes in the animals' condition or eating behavior. Calculations alone do not ensure success. Individual variations among horses must also be kept in mind, and the ration may have to be altered for "easy keepers" or "hard keepers." Differences may be influenced by temperament, previous nutrition, size, age, and weather conditions.
This discussion refers only to the "normal" or "average" horse and should be used only as a guideline. Proper individual feeding still depends on the feeder's careful observation and good judgment. The owner also needs to determine what body fat condition score they desire. This will change the requirement as much as the other factors mentioned. Calculations cannot replace good horsemenship.
The most serious nutritionally related problems in mature horses are colic and founder. Colic, or abdominal pain, is often associated with impactions and twisted intestines in the horse. Sudden changes in feedstuffs and diets with low-fiber content or small particle size are frequent causes. Laminitis, on the other hand, is a disease of the hoof that causes severe lameness. There are many causes of laminitis (founder), but overeating high-energy concentrates is probably the most common.
Research indicates that maximal rate of gain is not necessarily associated with maximal soundness. The energy density of the ration seems to be the culprit, combined with mineral imbalances. Developmental orthopedic diseases including physitis, OCD, and contacted tendons are problems most commonly associated with fast growing foals. These problems can be minimized by decreasing the rate of gain (decreasing energy intake) and by paying close attention to mineral balances, protein levels, and plenty of exercise.
The following feeding management practices assist horsemen in achieving good results with minimal problems.
Class of Horse___________________ Owner's Name____________________ _____Mature horse at rest Address_________________________ _____Mature horse at moderate work Breed of Horse____________________ _____Mare in last 90 days of pregnancy Weight of Horse__________Age______ _____Mare in peak of lactation (first 3 months) _____Growing foal ______Mature weight Dig Energy Dig Ca P Vit A Protein 1000 A. Your horse's daily _____Mcal _____lb _____g _____g _____IU's requirements I II III IV V VI B. Ration lbs of X(Mcal/lb) X(C P/lb) X(Ca/lb) X(P/lb) X(1000 IU's/lb) Feedstuff each =Mcal =lb C P = g Ca = g P = 1000 IU ________ _____ X(___)=___ X(___)=___ X(___)=___ X(___)=___ X(___)=___ ________ _____ X(___)=___ X(___)=___ X(___)=___ X(___)=___ X(___)=___ ________ _____ X(___)=___ X(___)=___ X(___)=___ X(___)=___ X(___)=___ ________ _____ X(___)=___ X(___)=___ X(___)=___ X(___)=___ X(___)=___ ________ _____ X(___)=___ X(___)=___ X(___)=___ X(___)=___ X(___)=___ C. Total ___lb _____Mcal _____lb _____g _____g ____1000 IU's supplied by ration D. Horse's _____Mcal _____lb _____g _____g ____1000 IU's requirement E. Needed _____Mcal _____lb _____g _____g ____1000 IU's nutrients F. Instructions 1. Determine the class of horse and record requirements from Table 1 and 2 in line A. 2. List ration ingredients and pounds of each in the appropriate columns. 3. Be sure ration ingredients in B do not exceed 2-2.5% of body weight. 4. Obtain feed compositions from Table 4 and record in cols. II, III, IV, V, and VI. 5. Multiply lbs of each feed (col. I) times each value in cols. II, III, IV, V, and VI. 6. Total the nutrients from each source to get total in ration (line C values). 7. Copy nutrient requirements from line A to line D. 8. Subtract line C values from line D values and record any deficiencies in line E.
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