What are Essential Amino Acids in Protein, and Why Do They Matter?

Nutrition articles frequently refer to protein quality and essential amino acids. When we use the term crude protein, we are essentially talking about a calculation based on measured nitrogen. Protein is about 16% nitrogen by weight, so if we measure the amount of nitrogen and multiply it by 6.25, this gives us a measurement of crude protein. It does not tell us anything about the quality of the protein. If you tested pure nitrogen this way, it would be 625% protein!

Digestible protein is that amount of the protein that is actually digested by the animal. In an over simplified example, if you fed 100 grams of protein and measured 50 grams in the feces, the protein would be 50% digestible.

What is really important to simple stomached animals (horses included) is the content of essential amino acids in the protein. We commonly talk about 10 essential amino acids (EAA), the amino acids that must be in the diet as the animal cannot synthesize them. These are:

  • Phenylalanine
  • Valine
  • Threonine
  • Tryptophan
  • Isoleucine
  • Methionine
  • Histidine
  • Arginine
  • Leucine
  • Lysine

A common memory aid in many nutrition texts books is to use the first letters of these 10 as PVT TIM HALL. (All of you who had a non-ruminant nutrition course still remember this acronym!)

The other 12 amino acids can generally be synthesized in the body and do not need to be in the diet, although there must be a supply of appropriate substrate to produce them. Animal nutrition text books cover this topic in excellent detail.

Limiting Amino Acids

Limiting Amino Acids

When we talk about limiting amino acids, these are the essential amino acids most likely to be restricting the use of the total amount of amino acids present. In most species, lysine is the first limiting amino acid, with methionine and threonine close behind. We commonly talk about amino acids as the building blocks of protein. If you are once you run out of an essential amino acid, you cannot build any more animal protein and the rest of the amino acids are used inefficiently for energy.

If you have a horse on a diet that is calculated to have adequate “crude protein”, but essential amino acids are not present, the horse simply cannot use the protein to build and maintain muscle, hair, hoof and skin and you will see changes in the appearance of the horse, such as loss of muscle mass, rough hair, scaly hoof surface.

Does My Senior Horse Need Calories or Protein?

hand feeding red sizeThere are some common questions come up when we talk about what happens to horses as they age and why their bodies change shape:

  • Does my good old horse need more calories (energy) or more protein?
  • He is out on good pasture and is holding his weight, but his hair coat looks dull and he has lost muscle mass.
  • She looks a little thin, should I add some fat/oil to her diet?

These are all apparently simple questions, but actually we need to look at the nutrient supply and purpose a little closer.

Calories from fat/oil, digestible fiber (structural carbohydrates and starch & sugar (non-structural carbohydrates) are the key energy sources for horses. If a horse is thin, that tells us that the horse needs more Calories to maintain fat cover measured by Body Condition Score system. Those Calories can be added from extra fat/oil, extra digestible fiber or additional starch and sugar. Vegetable oil contains 2.25 x the Calories per pound of carbohydrates and is a safe way to add Calories. Switching to a highly digestible fiber source (better quality forage, added beet pulp etc.) can also add Calories of digestible energy (DE). It takes 2-3+ pounds of added feed to add 1 pound of gain, depending on the feed.

Adding Calories alone will not bring back the muscle mass. This will require added protein (really added essential amino acids, particularly lysine, methionine and threonine, the first 3 limiting essential amino acids). If a horse is getting adequate crude protein, but the protein is of limited quality and is low in one or more essential amino acids, the horse will not be able to utilize it fully to maintain or restore muscle mass. This is why it is essential to know the quality of the protein in feeds, particularly these first 3 limiting amino acids.

A common situation is an old horse retired to a grass pasture. It may be difficult for the horse to consume enough to maintain body condition, thus the horse loses weight. The grass pasture may also be low in crude protein and certainly low in essential amino acids, so the horse also loses muscle mass. Tough combination for an old friend!

The good news is that this can be reversed with the use of a well-designed senior horse feed providing both Calories and essential amino acids!

Feeding Sunflower Seeds to Horses

Sunflower Seeds_Snack and Black Oil_BRSunflower seeds come in 2 basic classifications with some specialized varieties in each. Black oil sunflower seeds are primarily produced for sunflower oil production, and striped sunflower seeds are primarily produced for confectionary/human consumption.

  • Black oil sunflower seeds will be about 17% protein, 44% fat and 24% neutral detergent fiber (NDF).
  • Striped sunflower seeds will be about 16% protein, 24% fat and 40% NDF.

The hull of the sunflower is fairly tough and is not very digestible and the horse may not break all of the hulls when eating the seeds, so some may pass thru undigested. (The birds in your pasture will appreciate this!).

The black oil sunflower seeds are most readily available for purchase in bagged form as they are also popular for feeding birds and are the most widely used by horse owners. The oil content of black oil sunflower seeds is about 29% Omega 6 fatty acids and about .09% Omega 3 fatty acids. The oil is high in polyunsaturated fatty acids, which is why it is popular for human use.

The key element to consider in deciding if there is a good reason to use black oil sunflower seeds is to consider what you are actually adding to the diet and at what cost.

  • Current bagged retail price may be about $16.00-$20.00 per 20 pound bag.
  • This translates to $1600-$2000 per ton, which is fairly spendy for a horse feed!

If you feed a pound of black oil sunflower seeds, you are adding about 7 ounces of oil (less than a cup) and 2.72 ounces of protein with minimal digestible NDF or other nutrients. If you buy bulk soy oil, you should be able to add more oil at lower cost by adding straight oil and you will have a better Omega 6/Omega 3 ratio.

Black oil sunflower seed use for horses needs to be assessed basis what the ingredient actually adds to the diet and what the cost is compared to other ingredients or feeds.

Selenium Levels for Horses

Henry MusclesAs a horse owner, you may have heard about selenium levels and that you need to be concerned with them.  But why?

Technical reason: selenium is a key trace mineral in equine diets because it is a major component of glutathione peroxidase, which is an anti-oxidant enzyme, as well as several other enzymes.

  • Selenium also has an important interaction with Vitamin E.
  • Selenium and Vitamin E together are essential for both anti-oxidant benefits and for reducing the risk of certain muscle problems such as white muscle disease and exertional rhabdomyolysis syndrome.

Why you should care: Because selenium can also be toxic at higher intakes, it is also the only trace minerals regulated by the FDA.  Most of the U.S. is selenium deficient in soils (and thus toxicity is not an issue in those areas), but there are some areas with high selenium in the soil where some plants accumulate unacceptable levels of selenium in forage and may cause chronic toxicity. If you aren’t sure about the levels where you live, ask area horse owners, farmers, or your local extension office.

How much is in the feed?

In the case of selenium, the label guarantee, which is “added” selenium, is listed in ppm = parts per million = milligrams per kilogram. The actual content will be slightly higher as there is naturally occurring selenium in the ingredients. The labeling requirement is based on added selenium per FDA guidelines.

  • Premium horse feeds are commonly tagged at 0.6 ppm selenium, or 0.6 mg/kg of feed.
  • This equals 0.273 mg per pound of feed. (0.6 mg/kg divided by 2.2 kg/lb. = 0.273 mg per pound of feed)
  • Thus, if you feed 5 lbs per day of a 0.6 ppm selenium feed, you are providing 1.365 mg of selenium per day.

FDA requirement limits added selenium in feed to a maximum of 0.3 ppm concentration in total diet. This is why the maximum on complete feeds – feeds that include enough fiber to replace the hay/pasture portion of the diet – is 0.3 ppm.

On feeds which can be fed at a maximum of 50% of the diet (not that horse owners generally feed it that high), the limit is 0.6 ppm added selenium. Chronic selenium toxicity occurs at about 10X the FDA limit, so there is a pretty good safety margin.

How much does a horse actually need?

A horse’s basic daily requirement for selenium is 1-3 mg per day.  Some chronic selenium symptoms might appear above 10-15 mg/head per day.

To figure out what your horse is consuming, have your hay/pasture supply tested, and then add the amount it is consuming from the hay, to the amount it is consuming from any feed & supplements, and you will know if you need to make any adjustments to your horse’s overall diet.  Depending on your area, it may also be useful to consider intake from water sources.

Manage Pasture to Help Control Horse Feed Costs

Widgy in Grass_BRManaging pasture can be a very important tool in controlling feeding cost for all livestock, particularly horses being kept on small acreages.  If pasture is going to provide a substantial amount of the required nutrition for a horse, it takes about 2-3 acres per 1100 pound adult horse.

There are a number of key steps in managing pastures, particularly small acreages

  1. Do not turn the animals out on pasture too early in the spring.  Forages need some growth to recover from the winter and allow root systems to develop.
    1. Do not turn animals out on tall cool season grasses such as brome grass and orchard grass until the plants are 8-10 inches tall.
    2. If pastures are short cool season grasses such as Kentucky blue grass or rye grass, the plants should be 6-8 inches tall before grazing.
    3. If you do not know your pasture composition, err on the side of allowing adequate growth before grazing.
  2. Remove animals from the pasture when plants are grazed down to 3-4 inches in height.  Grazing too early or too long and allowing animals to eat the grass off too close to the ground will kill the grass and turn the pasture into a dirt lot where the only green plants are weeds, requiring expensive renovation.
  3. If you have limited acreage, consider purchasing some temporary fencing so that you can rotate the pasture.
    1. The outer fencing should be a safe, permanent fencing.
    2. You can cross fence the pastures with temporary fencing such as capped steel posts and appropriate electric wire.
    3. By allowing the animals to graze one section, then moving them to another section to allow the first section to recover, total pasture yield can be increased substantially, helping to control total feed costs.
    4. Clip and drag the pastures after you pull the animals off to control weeds and control parasites and flies.
  4. Make certain that fresh clean water is available at all times and that salt is available at all times.  If you are not feeding a balanced horse feed or ration balancer, offer appropriate mineral free choice as well.
  5. If space is very limited, keep a dry lot area where animals can be fed and watered to prevent areas of pasture from being overgrazed.
  6. Check with your local extension team for additional recommendations for your area and for recommendations on fertilizing pastures.  Dr. Krishona Martinson at the University of Minnesota, St. Paul, MN has published some excellent guidelines for pasture management.

A small investment in supplies to allow pasture to be managed and rotated can pay for itself in higher pasture yields.  Managing the pastures and selecting the right feeds can help manage total yearly costs as well as improve animal health and condition.

Spring Pasture Time for Horses!

Toby GrazingIntroducing horses to growing pasture is a welcome event each year, yet must be approached with caution. Introducing the horses to pasture too soon in the season or for too long a time period can be bad for both the pasture and the horses.

The following are some guidelines to consider:

  1. Do not turn the horses out on pastures too early. Grass needs time to recover from the stress of winter and should be allowed to re-grow to 6 to 8 inches in height, depending on the species, to allow roots to grow and to store some energy before being grazed.
  2. Horses should be fed hay before going out on pasture the first time. Do not turn them out with empty stomachs!
    1. Initial grazing should be limited to 15 to 20 minutes and gradually increased each day by 15 minutes until the horses are out for about 4 or 5 hours, at which time they can be allowed unrestricted time.
    2. If horses are allowed too much initial grazing time, the risk of digestive disturbance is increased as it takes the microflora in the gut some time to adjust to the difference in forage source.
  3. Do NOT overgraze! Pastures should not be grazed to below 3-4 inches in grass length or you will wind up with a dirt lot fairly quickly. Some weeds are also hardier than most grasses, so if pastures are over grazed, weeds will become more prevalent.
  4. Remember that cool season grasses growing very rapidly can be high in plant sugars (fructans), so caution is in order.
  5. Grazing muzzles might be an option for helping reduce rapid intake.

Proper introduction of horses back on pasture needs to be managed for the health of the horses and the health of the pastures!

Is City Water OK for My Horse?

The question comes up from time to time if municipal water supplies are OK for horses. The concern is generally related to the added chlorine or added fluoride in the water. The water is treated with chlorine to minimize risk of bacterial contamination, and the fluoride is added to improve human dental health.

The chloride may change the aroma and taste of the water. Taking horses to facilities with chlorinated water can sometimes reduce water consumption. Reduced water consumption may impair performance and may also increase the risk of impaction colic. Horses do adjust to the difference in taste and aroma over time, but this may take a few days. It is routine in many barns to flavor the water with something like wintergreen or peppermint at home, then flavor the water at the new location or while traveling to match the home water.

  • NOTE: Do NOT use soft drinks that contain caffeine or any material containing caffeine as these can trigger positive drug tests!

The fluoride levels in municipal water supplies are normally at about 0.5 to 1.0 mg/liter of water. The maximum dietary allowance for horses is about 4-8 mg/liter (Source: Mineral Levels in Animal Health-Diagnostic Data, Second Edition, R. Puls), so the level in municipal water is well below any levels associated with heath risk for horses.

Municipal water should be OK for horses. When changing water sources, consumption should be monitored to make certain horses continue to consume adequate water with flavoring the water being an option when traveling. As always, salt should be available free choice.

Horse Feed Tag Mathematics

It takes some time and math skills to properly understand how the guaranteed analysis relates to what your horse is actually taking in every day!

It takes some time and math skills to properly understand how the guaranteed analysis relates to what your horse is actually taking in every day!

We often receive questions from horse owners, wondering what the various units of measure on horse feed tags mean, and how they can use those units to figure out what their horse is consuming…and wondering why in the world they have to be so confusing, too!

In short, feed companies use the units of measurements on nutrients that we do, because we are required to. Why? Because horse feeds and other livestock feeds are labeled as required by AAFCO (American Association of Feed Control Officials) and the various state Feed Control regulations.  These regulatory bodies establish the units which are to be used for each nutrient in tag guarantees.

To break it down, there are 4 common units used on feed tags.  To help you understand them all, here’s a quick overview of how they work, along with examples of how to do the appropriate math:

Protein, amino acids, fat, fiber and macro minerals (calcium, phosphorus, magnesium and potassium) are listed as a % minimum or maximum.

  • To calculate the amount supplied per pound, you can convert % to a decimal fraction by moving the decimal point 2 places to the left, then multiply by the pounds fed.
  • As a horse’s daily intake requirements are sometimes given in grams, we can convert those pounds of intake to grams as well.
    • For those of us that are mathematically challenged, a quick Google search of “pounds to grams” will provide a handy conversion calculator!

Example:

  • A feed that is 14% protein would contain 1 lb x 0.14 = 0.14 lb of protein in 1 pound of feed.
    • If you want to measure in ounces, there are 16 ounces per pound, so the same pound of feed would contain 0.14 x 16 = 2.24 ounces of protein.
    • If the requirements are given in grams, we know that there are 453.6 grams per pound, so the feed would contain 453.6 x 0.14 = 63.5 grams of protein per pound of feed.
  • Feeding 5 lbs of this feed per day, results in feeding 0.7 lbs, or 11.2 ounces, or 317.5 grams, of protein per day.

Trace minerals (copper, zinc, manganese and selenium) are expressed as “ppm” or parts per million.

  • One part per million is the same as one milligrams per kilogram.
  • 1 kilogram = 2.2 pounds.

Example:

  • Premium horse feeds are commonly tagged at 0.6 ppm selenium.
  • This is 0.6 mg/kg of feed. This equals 0.273 mg per pound of feed.
  • 0.6 mg/kg divided by 2.2 kg/lb. = 0.273 mg per pound of feed
  • Feeding 5 lbs of this feed per day, results in feeding 1.365 mg per day of selenium.

Vitamins A, D and E are expressed in IU/lb.

  • An IU is an International Unit and is based on the effectiveness of a particular vitamin.
  • There are some rather complicated conversions of different Vitamin sources to International Units, which is why animal requirements are given in International Units, so no further conversion is needed.

Example:

  • A feed that lists 100 IU/lb of Vitamin E, fed at 5 lbs per day, provides 500 IU’s per day.

Vitamin C (or Ascorbic acid) and Biotin are normally expressed as mg/lb or milligrams per pound.

  • Usually only tagged on senior horse feeds.
  • Requirements are in mg of intake per day, so no further conversion is needed.

Example:

  • A feed that lists 75 mg/lb of Vitamin C, fed at 5 lbs per day, provides 375 mg per day.

Still confused?  Don’t worry about it. Just leave us your questions in the comments section below, and we’ll be happy to help you out!

Dehydration in Horses – A Year Round Concern

We sometimes think of dehydration as only a hot weather concern. Horses (and people) can experience dehydration any time they are losing more water from their body than they are taking in to maintain fluid balance. This can be a problem in warm humid conditions, but can also be a problem in warm dry conditions or cold dry conditions. This is a definite concern in cold weather when access to water may be restricted due to frozen water supplies.

Dr. Lon Lewis presented this very handy table on dehydration several years ago in his book Equine Clinical Nutrition: Feeding and Care.

% Dehydration Possible Symptoms
Less than 5%
  • No detectable abnormalities are generally present.
6%
  • Skin becomes slightly inelastic with a pinch test time of longer than 1 second
8%
  • Capillary refill times goes from normal of 1.5-2 seconds to about 3 seconds
  • Mouth and mucous membranes may be dry
  • Generally the feces will be dry and urine output may decrease
10%
  • Severe skin elasticity
  • Capillary refill time will be over 3 seconds
  • Extremities will be cold and there may be weakness
12% and greater
  • Inability to stand
  • Shock
  • Muscle twitching
  • Weak pulse
  • Death can occur at or above this level

For an 1100 pound horse horse, 5% dehydration would mean the horse has lost about 55 pounds of water or about 6.875 gallons (1 gallon = 8 pounds of water).  At 12% dehydration, the 1100 pound horse has lost 132 pounds of fluid or about 16.5 gallons.

You may also see loss of performance and visual signs without doing these tests. I see this in the arena when I am judging, particularly during the hot humid conditions. I confess I have experienced some of the same symptoms when judging a long horse show while wearing a coat and tie! It takes me about 24 hours to rehydrate!

If you are not familiar with the pinch test or capillary refill time, it is a good idea to discuss these tests with your veterinarian as these are important quick tests to check the status of your horse as a part of general first aid along with being able to check pulse and heart rate. In general terms, the skin pinch test is best done over the shoulder or over the back. Capillary refill time can be checked by pressing on the gum to compress the blood vessels, then timing the return to normal color.

Dehydration may be due to many different factors and can contribute to impaction colic as well as heat stress or heat stroke. Dehydration may occur in cool or cold weather as well as hot weather. Horse owners should visit with their veterinarians to make certain they know how to recognize the various symptoms of dehydration.

Having fresh clean water available at all times and providing access to salt free choice (loose salt may be preferred during cold weather) all year long are required to help reduce the risk of dehydration.

Lewis, Lon D. DVM, PhD., Equine Clinical Nutrition: Feeding and Care, Williams & Wilkins, 1995, Table 17-1, page 392.

Feeding the Hard-Keeper Horse that has Ulcers

My horse is a hard keeper, and is also prone to ulcers.  What should I feed?

Horses vary a great deal in what level of nutrition is required to maintain desired body condition and muscle mass.  Horses have not been selected or bred based on feed efficiency, feed conversion or rate of gain, so there a lot of variation between horses.

A horse that is a hard keeper may require more Calories per day to maintain body condition than an easy keeper doing the same work.  One way to help this horse will be to feed high quality forage that has a high Relative Feed Value (RFV) that is associated with higher Digestible Energy (DE) per pound.  A good choice might be an alfalfa or alfalfa grass mix that was cut at early maturity so it has fine stems and lots of leaves.  This hay could be fed free choice or at least 3-4 times per day at a rate of about 2% or above BW/head/day.

The hard keeper may also benefit from a commercial feed that is high fat (8-9 % or higher) and controlled starch and sugar (so it can be fed at higher levels) with amino acid fortification (lysine, methionine and threonine) to help maintain muscle mass.  This feed can be fed a minimum of 2 times per day, and preferably 3-4 times per day so that the quantity being fed can be increased while controlling risk of starch overload through smaller individual meals.  The quantity can be increased with the desired forage to produce weight gain, and then adjusted to maintain desired weight.

A high fat supplement that is 20+% fat can also be used as a top dress.

This feeding plan may also be useful in reducing the risk of having ulcers redevelop after a horse has been treated with appropriate medication.  Free choice forage or pasture is a good option so the horse’s stomach is not empty for long periods of time.  Alfalfa contains levels of calcium and magnesium that may be useful in buffering acid in the stomach.  High fat, controlled starch feeds fed in small meals at frequent intervals may also be useful in reducing the risk of re-occurrence.   A feed that contains specific metal amino acid complex trace minerals may also help improve gut health and digestive tract tissue integrity in the stomach.