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Nutrition

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selecting the diet | calculating forage, concentrate, and pasture intake | analyzing feedstuffs | nutrient requirements | evaluating and correcting diets | Pearson square procedure  

The following are a few definitions important for understanding nutrition:

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There are many factors that affect the daily feed requirements of a given animal. Some of these are listed below:

1. Breed and size
2. Age (foal vs. adult)
3. What the animal is used for (pleasure, broodmare, competition, etc.)
4. Environment and climate
5. Health status (teeth and parasite control)
6. Attitude (calm or high strung)

Introduction: Good pasture forage and/or hay can supply sufficient nutrition for a typical mature horse. The addition of concentrates (grains) may be required for animals that are growing, working, or nursing a foal. Care should be taken to prevent animals from becoming overweight on good pastures or by over feeding. The following table lists the expected amounts of forage and concentrate a horse may consume depending on its class. Horses will generally consume 1.5 to 3.5% of their body weight in feed per day. Ideally, to maintain proper gut function, it is recommended that at least 1% of the horse’s body weight is fed as forage.

Table #3 - Forage and concentrate a horse may consume:

When choosing a particular hay, the following suggestions should be used:

1. Consider the color and cutting dates. Green, freshly cut hay generally contains more vitamins and nutrients. Third and fourth cutting hays may be excellent quality, but too rich in protein and low in fiber for the particular needs of the horse.
2. Different types of hay vary widely in amounts of protein, energy, vitamins, and minerals. A forage analysis is the only way to be sure of the nutrient levels provided by a particular feed.
3. Pick the hay quality that meets the specific horse’s needs for stage of growth, age, and level of activity. Often, the highest quality hay is "too good" and can create digestive system problems.
4. Evaluate the hay for general condition. Do not feed dusty or moldy hay. Any mold or dust can cause chronic respiratory problems. (See heaves on page E305 for additional information.)

When choosing a specific grain, the following suggestions should be used:

1. Evaluate the color and smell. All grains should be brightly colored and have no foul odor. Changes in color and smell may indicate bacteria or mold contamination. Avoid grain that is dirty or contains rocks, sticks, etc.
2. Grain that is high in moisture or light in weight (lbs. per bushel) will have a lower density of nutrients.
3. Do not overfeed grains. Feed the appropriate amount for the age, stage of growth, and level of activity. Many mature horses, doing light work, do not require any grain if they are on good pasture or are fed quality hay.

Calculating Forage, Concentrate, and Pasture Intake: It is always important to weigh each forage or concentrate that is being fed to the horse. If the horse is grazing pasture, the amount of pasture being consumed can be determined by calculating all the digestible energy (DE) the horse is receiving from known quantities of hay and/or concentrate. Next, subtract the DE intake from hay and/or concentrate from the horse’s daily energy requirement. Then, to get the horse’s estimated dry matter intake of pasture, divide this number by the pasture’s calculated energy density. For example, a yearling that weighs 725 pounds with an average daily gain of 1.25 lbs/day should require about 20.4 Mcal DE/day (taken from table #4). If this yearling is eating 5 lbs of sweet feed (6.75 Mcal DE total) and 6 lbs of mature alfalfa hay (5.64 Mcal DE total), then it must be consuming around 8 Mcal of DE from pasture. The horse in this example is grazing on a pasture that is mostly orchard grass that has a 1.04 Mcal/lb DE. This means that this yearling must consume about 8 lbs of pasture dry matter per day to meet his energy requirements. Realize that this is just an estimate of the pasture the horse is consuming and that miscalculations can occur. Many miscalculations occur because of under or over estimating the amount of hay and grain the horse is consuming.

Step 1 - Choose the Feeds to be Tested: The feedstuffs chosen for analysis should form the basis of the ration. This will usually include samples of each different type or cutting of hay and any other roughages. The nutrient composition of roughages varies greatly from year to year and from farm to farm, making yearly analysis a necessity.

Home raised grains should be tested every 2 years to check nutrient quality compared to expected values. Nutrient composition of feeds such as corn and soybean meal vary significantly, and depend upon variety, weather, and processing conditions. Frequent testing of the energy and protein ingredients in mixed feeds, such as growing or lactating rations, is also necessary. 

Step 2 - Collect the Feed Sample: Accurate feed analysis begins on-farm with proper feed sampling techniques. Collection of a representative feed sample is the most important step in feed analysis. Use these guidelines when collecting feed samples:

Hay Samples: To sample hay properly, a hay core sampler is a necessity. Many feed company representatives, county extension agents, and a few veterinarians have core samplers. Place the hay corer into the middle of the narrow end of square bales, or the rounded side of large round bales, and drill to the center of the bale. When sampling from large round bales, an extender is added to the core sampler so that the bale center can be reached. Proper sampling practices ensure that the sample obtained will include the same proportion of leaves and stems that is present in the entire bale. Sample a minimum of 10-12 bales from different locations in the storage area. Better yet, set aside bales that are to be sampled as the hay is being stored. This will avoid hay being buried under or behind other hay in the storage area and allow a more representative sample to be collected. Mix the samples together in a clean, dry plastic pail. A two-handful subsample sealed in a plastic bag and well-labeled is sufficient for laboratory analysis. Flakes of hay or samples grabbed by hand are not representative samples and analytical results will be inaccurate. Many labs will refuse to accept inappropriate samples.

Dry Grains: Sample dry grains by hand or with a grain probe. Sample from various areas in the storage bin, and mix all subsamples in a clean, dry pail. Remove two handfuls of the combined mixture and place the sample in a clearly labeled plastic bag to be sent to the lab.

Pasture: Because horses tend to be "spot" grazers, pasture analysis is more difficult. Generally, only those areas that are heavily grazed should be sampled, rather than the entire pasture. Collect random handfuls of forage from several locations in the heavily grazed area. These samples should be collected at about the same height the animals will be grazing the forage. Once collected, the samples from a certain pasture should be combined and allowed to air dry. Air drying is accomplished by hanging the forage inside a burlap bag for approximately a week. Once dried, these samples can be sent to a laboratory for analysis.

Step 3 - Submit the Feed Samples: Once the representative sample is properly collected, the process is not yet complete. Samples must be accurately labeled and described. Feed analysis laboratories require a completed "sample input" form to accompany the samples. The input form information and proper sample identification are extremely important to enable the lab to perform the correct analytical procedures. When submitting hay samples, indicate the type (grass, mixed or legume) and appropriate cutting (i.e. first, second, etc.). Follow these general guidelines to determine the type of hay being submitted for analysis:

GRASS = < 25% legume (alfalfa, clover, etc.) in the sample
MIXED = 25-75% legume in the sample
LEGUME = > 75% legume in the sample

A good policy to follow when submitting samples is to include any and all information that will help the laboratory do the best job possible. A list of available laboratories can be obtained from the Cooperative Extension Service.

Energy: This is often the key area of focus when evaluating a ration. Horses that are nursing, growing, or doing heavy work have relatively high energy requirements. Cold, severe weather conditions increase energy needs. The following list contains equations for determining the energy requirements (digestible energy) for different classes of horses:

Protein: Protein is also an essential component to any diet. Broodmares and growing animals require additional protein in the diet. In general, if the diet contains sufficient energy, it often contains sufficient protein.

Evaluating Body Condition: Determining the horse’s body condition is essential in making any diet changes. Use the information found on page B950 to help determine a horse’s body condition before making any changes to a ration.

Example A: The yearling in this example is currently eating 2.5% of her body weight or 18.13 lbs of alfalfa hay (0.94 Mcal/lb DE and 16% protein) per day. The yearling, however, has a body condition score of only a three (3). No mineral is provided. Good water in a heated tank is readily available. Using information from table #4, note that a 725 pound yearling filly needs approximately 20.4 Mcal/day of digestible energy (DE) and 12.6% protein in the diet.

Step #1: Determine if this yearling is consuming the appropriate amount of both forage and concentrate by using the suggestions found in table #3.

According to table #3, most yearlings should consume 1.0-2.5 % of their body weight in forage and 0.5-2.0% of their body weight in concentrate.

In this example, the yearling seems to be consuming the maximum amount of forage per day; however, because her body condition is lacking, she still needs additional energy. Concentrates are usually great sources for additional energy and should make up some proportion of her ration. It is also determined that the yearling can not consume more than about 18 lbs total of feed per day.

Step #2: Calculate the digestible energy (DE) provided by the alfalfa hay to the yearling. This is done by multiplying the Mcal/lb DE of the alfalfa by the amount the yearling is consuming.

0.94 Mcal/lb X 18.13 lbs = 17.04 Mcal DE Total

Conclusion: Based on the fact that the yearling has a BCS of 3.0 and her Mcal DE requirement is 20.4, she requires additional energy. This calculation also supports the need for additional concentrate in the diet.

Step #3: A sweet feed with 1.40 Mcal/lb DE and 10.8% protein is chosen to be used as the concentrate portion of the diet. It is also determined that the owner will feed 18 lbs total of both the hay and sweet feed. This means that each pound of feed consumed must contain an average of 1.13 Mcal/lb DE (20.4 / 18 = 1.13). To determine the exact amounts of hay and sweet feed to feed, a Pearson square method is being used:

A. Draw a square similar to the one found in B.

B. Place the desired nutrient amount or percentage (DE, TDN, protein, etc.) needed to balance the requirements of a specific animal in the center of the square. In this example, 1.13 Mcal/lb of feed is her digestible energy (DE) requirement if she will only consume 18 lbs of feed total.

C. Place the name and nutrient amount of the primary feed being fed (usually pasture, hay, etc.) in the lower left hand corner, and the name and nutrient amount of the supplemental feed in the top left hand corner.

D. Calculate the difference between the feedstuff to be fed and the basic nutrient requirement in the center of the square. This number should be placed in the opposite corner following the arrows. In this example, 1.40 minus 1.13 = 0.27, and 0.94 from 1.13 = 0.19.

F. Now the total amount to be fed of both the grain and hay can be calculated.

Amount to feed:

• Take the total parts alfalfa hay (or sweet feed) and divide it by the total parts in the ration.

Alfalfa: 0.27/0.46 X 100 = 59% of the total ration should be hay
Sweet feed: 0.19/0.46 X 100 = 41% of the total ration should be grain

• Take the percent of the ration that should be alfalfa hay and multiply that by the total amount of the ration in pounds (18). Do the same for the sweet feed.

Alfalfa hay: 0.59 X 18 = 10.6 lbs hay on a dry matter (DM) basis
Sweet feed: 0.41 X 18 = 7.4 lbs grain on a dry matter (DM) basis

• Take the Mcal/lb DE of the alfalfa hay and multiply it by the amount of alfalfa in the diet. Do the same for the sweet feed. Add both amounts together and this gives the total Mcal DE in the ration.

Alfalfa hay: 0.94 Mcal/lb DE X 10.6 lbs = 9.98 Mcal DE
Sweet feed: 1.40 Mcal/lb DE X 7.4 lbs = 10.36 Mcal DE
Total Mcal DE: 9.98 + 10.36 = 20.34 Mcal DE total

Conclusion: The ration now meets the energy requirements for this yearling. Looking back at the percentages of hay and sweet feed to be fed (59% and 41%), and comparing these to the ones found in table #3, the yearling should be able to consume the above amounts of hay and sweet feed.

Step #4: Next, determine if the current diet meets the yearling’s protein requirements of 1.99 lbs or 12.6%.

• Take the percent protein of the alfalfa hay and multiply it by the amount of alfalfa in the diet. Do the same for the sweet feed. Add both amounts together and this gives the total pounds of protein in the ration. Convert this number back to a percentage by dividing the total pounds of protein by the total pounds of the diet being fed.

Alfalfa hay: 16% X 10.6 lbs = 1.70 lbs of protein from the hay
Sweet feed: 10.8% X 7.4 lbs = 0.80 lbs of protein from the sweet feed
Total lbs of protein: 1.70 + 0.80 = 2.50 lbs of protein total
2.50 / 18 = 13.8% protein

Conclusion: The ration actually exceeds what the yearling may require for protein. In some cases, it may be necessary to select a hay that still gives similar energy levels but has a lower protein. For now, it is recommended to focus on the energy and see if the yearling gains some extra body condition. Once this is accomplished, changes can be made to the protein levels. This yearling also needs a free-choice trace-mineral salt source.

Example B: A current horse owner just purchased a new 4 year old gelding to use for pleasure riding. This horse weighs 1,100 lbs and is in good body condition. Determine how much of the current diet being fed to the other horses this new horse requires. The current feeds on hand include a concentrate mixture (1.30 Mcal/lb DE) and timothy hay (0.80 Mcal/lb DE). From table #4 it is determined that this horse has a total DE requirement of 20.5 Mcal/day.

Step #1: To start with, determine how much of the diet should be roughage. Use the suggestions in table #3 to help estimate the amounts that should be fed. In this example, the horse is not expending excessive amounts of energy, so the bulk of his ration will be hay and a minimum amount will be concentrate.

Amount of hay = 2.0% X Body Weight
0.02 X 1,100 = 22 lbs of hay on a dry matter (DM) basis

Step #2: Calculate the digestible energy (DE) provided by the timothy hay to the gelding. This is done by multiplying the Mcal/lb DE of the hay by the amount the gelding will be consuming.

0.80 Mcal/lb X 22 lbs = 17.6 Mcal DE Total

Conclusion: Based on the fact that the gelding has a DE requirement is 20.5, he requires 2.9 Mcal DE/day (20.5 - 17.6) additional energy. The remaining DE should be supplied by the concentrate portion of the diet.

Step #3: Determine how much of the concentrate (1.30 Mcal/lb DE) should be fed in addition to the hay. This is done by simply dividing the amount of additional energy the horse requires by the amount of DE per pound of feed the concentrate contains.

2.9 / 1.30 Mcal/lb = 2.23 lbs of concentrate on a dry matter (DM) basis

Step #4: Because very few feeds are actually 100% dry matter (DM), convert the above amounts of hay and concentrate from a DM basis to an as-fed basis. To do this, divide each amount of hay and concentrate dry matter by the percent of dry matter in that feed (taken from table #4 or the actual concentrate feed bag).

Timothy hay: 22 lbs / 89% DM = 24.7 lbs of hay as fed
Concentrate: 2.23 lbs / 88.2% DM = 2.52 lbs of concentrate as fed

Conclusion: This means that the gelding really requires 24.7 lbs of hay and 2.52 lbs of concentrate to fill his nutritional requirements. Try this ration for the first few weeks to months and monitor the gelding’s body condition. If he becomes too heavy or too thin, adjust his ration as shown in Example A.

Summary: The information provided in the previous tables is based on averages for all animals and all feedstuffs. Different individuals within each class can have very unique nutritional needs. Because of this, use the horse’s body condition as the determining factor when making adjustments to a ration. Do not force a horse to eat exactly what is calculated on paper and neglect the horse’s actual body condition. The following suggestions can be used when trying to evaluate weight changes and rations:

1. Weigh the horse regularly over several weeks. If weighing is not a possibility, use the suggestions found on page B950 to calculate a horse’s weight. Also use the information about body condition scoring. Body condition is often a more reliable indicator of the nutritional status than simply using body weights. Realize that horses with the same weight will not have the same BCS. A horse with a BCS of 5 should be used as the standard; all other animals should be compared to this "average" horse. A horse with a BCS of 5 is not too fat or too thin; the ribs cannot be seen, but can be felt.
2. Calculate average daily weight gains for growing horses and use these to determine energy requirements.
3. Weigh each feedstuff and verify that the horse is really consuming the amounts used for calculations. Watch for horses that may waste some of the measured feed. If possible, feed the horse in feeders that are off the ground and have a "catch area" for smaller feed particles.
4. Have a feedstuff analysis performed on every feed with unknown nutrient values. Because the nutrient values differ so much between similar feedstuffs, table #5 should only be used as a general guide.
5. Provide plenty of clean, fresh water on a daily basis. Do not rely on snow for winter water supplies. To properly digest and move the feed through their digestive system, horses need plenty of water. Impactions and colic are common problems associated with a lack of hydration.

Converting crude fiber on a feed tag to digestible energy (DE) Mcal/lb: Many feed tags do not contain the actual DE; therefore, it is often necessary to use the crude fiber and crude fat percentages to determine the DE (Mcal/lb) of the grain mix. Use the following table to help make the conversion:

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