Healthy
Healthy
Healthy
Opinions on what constitutes proper nutrition for the horse vary as much as opinions on what is the best diet for humans.
Over the years, I have been struggling to find the right way, falling prey to many fads, and my horses paid for it.
The only thing that saved my horses generally, I guess, is the fact that they always were out 24/7, had good pasture, got free choice grass hay and were exercised a lot. I say generally, because I lost 4 horses to founder, caused at least partially by wrong diet.(too much grass, poor mineral balance due to mineral blocks and commercial supplements)
After following some more fads like feeding oil, free choice minerals and linseed and canola meal, I finally found Dr. Kellon and took some of her nutrition courses. www.drkellon.com. If you are serious about nutrition, I would highly recommend at least her basic course.
Common sense once more returned to my feeding program, my horses thrive and I feel finally really good about it. The basic idea is: find out what the horse needs, then find out what he gets from his food and supplement what is missing, if any. Although at one point I was totally convinced that horses “know” what they need, offering them free choice minerals turned out to be a disaster in the long term. Horses are like us, they have taste preferences and will eat too much of what tastes good and not touch other things they would need. For example, my horses totally overate on copper salt, but never touched the zinc salt, and these 2 minerals are so important to be in the right balance. Too much of each cancels out the other. As both are deficient in hay and soils in our area it is crucial that the horse consumes both in the right ratio. Another free choice supplement was alfalfa based, they just gobbled it up like candy. According to the manufacturer, they “needed” it.
The very best way to find out what to feed is having the feed tested. With hay, this is mostly fairly simple. One takes a sample from up to 20 bales and sends it to a lab like Equianalytical . http://www.equi-analytical.com/. Some horse owners however don’t have the luxury of being able to store a lot of hay and need to buy frequently from different sources. This complicates matters, but if the hay comes from the same region, a test of the first supply will give a good basic overview. Also, agricultural extension services have very good knowledge of the soil- and forage conditions all over the country due to the dairy industry. While this will not result in exact numbers, it still is much better than not doing anything or supplementing haphazardly.
With fresh grass, it also can be a bit complicated as it is not so easy to get a representative sample of the forage. But it still is way better than not doing it at all. With grain, there are usually analyses available online that are quite sufficient, esp. as one does not feed much grain anyway.
Water can also be a culprit and contain dangerous and toxic substances like arsenic and too much fluor, so testing a well or getting the analysis from the town if using public water supply is quite a must. Testing soils can also be a good clue, as plants need a balanced mineral profile to thrive. Esp. the right pH is of great importance.
If a horse is doing poorly or has unexplained health problems, testing the blood can reveal at least some deficiencies. Iron levels can be measured quite accurately, as well as selenium levels. Thyroid function tests are also helpful, and some vitamin deficiencies can also be detected. However, most minerals cannot be evaluated conclusively as the blood strives to be as complete as possible because it has to nourish the vital organs to keep the organism alive. To achieve this it draws nutrients from other tissues, esp. bones. Once the blood shows certain deficiencies there is most likely already a crisis within the body.
Hair analysis can also be helpful, esp. to detect toxic substances. For overall nutrition evaluation it may not be too helpful, but opinions diverge.
When talking about the sparse vegetation that wild horses have adapted to, many people assume that letting a pasture really run down and not fertilizing it might be equivalent of what a horse would get in the wild. Nothing could be further from the truth. Horses eating sparse forage in the wild cover large areas and in doing so they most likely meet a very diverse mineral profile. Horses overgrazing a pasture deplete it, their manure does not add back what the soil needs, and the plants are very stressed, containing much more sugar than normal. While many people feel a lot better seeing a horse on a very poor pasture and are horrified to put a horse out on lush grass of good height, more than likely this well maintained pasture is a lot healthier for the horse. Important is that it is mostly grass, and not much legumes. Many existing pastures have been planted for cows with high legume content and are therefore unsuitable for horses. Also many pastures contain alsike clover which is highly toxic to horses, but horses don’t seem to know that and eat it readily. Additionally, white clover thrives on eaten down and depleted pastures, and although not toxic like alsike clover, it still is a legume and not good for horses in any volume.
The following is an attempt to explain and summarize the most important aspects of nutrition to convey a rough overview. This subject is so comprehensive that it could easily fill a large book, and every detail seems so important that it is hard to stay brief and yet transmit the whole picture in context. In any event, the reader should not assume that after reading this page he/she has sufficient knowledge to feed a horse. It is merely meant to point out the importance and complexity of this subject and to encourage further reading and learning. Unless taking a course yourself, the best way to proceed is reading as much as you can and hire a competent person to help with composition of the diet.
At the end of this page you will find the names and contact information of some people who can help with figuring out what your horse may need.
Please, do not take horse nutrition lightly. Esp. with the surge of metabolic and immune diseases in horses, a balanced diet is the best insurance to keep a horse healthy, and when already compromised, it is a major stepping stone on the way back to health. We all are what we eat.
I believe, the most important thing to understand for anyone who feeds a horse is how his digestive systems works and thus realize its requirements and limitations, and also to understand what nutrients a horse needs in what quantities and for what reasons.
Let’s start with the digestive tract.
DIGESTIVE TRACT
In order to understand the nutritional requirements of horses, one first needs to understand their digestive system. Horses have the same requirements for energy, protein, vitamins and minerals as other animals but differ in the type and function of their digestive system, falling between a ruminant and non-ruminant.
Here is a rough schematic of the digestive system with approximate capacity of every section.
Non -ruminants (humans, pigs and dogs) digest carbohydrates, protein and fat by enzymatic action. Ruminants (cattle, sheep and deer) use bacteria in the fore stomachs to digest fiber by fermentation and use enzymatic digestion in the small intestines.
Horses have a dual digestive system. In the foregut, ahead of the cecum, enzymatic digestion takes place. 52 – 58% of the crude protein is digested there and virtually all soluble carbohydrates like sugar and starch. In the hindgut, bacterial or microbial digestion takes care of the fiber portion of the feed like oat hulls, beet pulp, hay, straw and pasture. Large quantities of volatile fatty acids are produced through this fermentation process and are subsequently absorbed. In essence, the horse’s hind gut is a huge fermentation vat. Lots of heat is created by this fermentation process, and this is what helps to keep horses warm. For that very reason it is imperative that they get enough fiber during the cold months, read: plenty of roughage, NOT grain.
For enzymes and microbes to be able to digest feed efficiently by breaking down the tough plant cell walls, the food needs to be well chewed and ground up. Hence the importance of healthy and well balanced teeth. Horses should see a qualified dentist at least once a year for this reason. All too often, horses suffer from digestive complications due to either lack of tooth care, or ignorant care. It is even more difficult to find a qualified dentist than farrier, esp. as the teeth are hidden from view and most horse owners have zero knowledge about how to check for problems. With the advent of power tools, many crimes are being committed in horses’ mouths, from ruining the chewing surface to removing too much tooth and so subjecting horses in their teens to being toothless. Horses’ teeth are of a certain length and keep erupting continuously. Usually they last a horse well into their 30ies if not compromised by overzealous dentists.
Pain free chewing also is necessary to release appropriate amounts of saliva, about 10 to 12 quarts a day. The more the horse chews, the more saliva is produced. Although equine saliva does not help as much with digestion as saliva in other species, it contains a high concentration of bicarbonate which helps buffer stomach acid. It also is rich in mucin which lubricates the esophagus. This is one reason why horses frequently choke when being fed a pelleted feed. It breaks apart readily, the horse does not chew enough, thus does not release enough saliva and not enough mucin is produced to help the food down the esophagus. And of course the smaller amounts of saliva can also lead to an overly acid stomach and thus to ulcers. If at all possible, horses should always be fed predominantly hay/roughage that requires a good amount of chewing. Lots of chewing also seems to have a palliative psychological benefit. If deprived, horses look for other ways to satisfy this chewing need like gnawing on fences and stall walls.
Stomach capacity of the horse is only about 8-15 litres (eight quarts equal about two gallons). Most people are unaware of this and think their stomachs are well filled after 2 flakes of hay and that this food will last them a long time. However, the emptying time of the stomach after filling can be about 12 minutes, and the rate of passage down the small intestine is about 1 ft/min. As a result food can go from the mouth to the cecum in as short a time as 1½ to 2 hours. The small volume of the stomach and rapid passage of food from the stomach is the reason horses eat almost continuously, and this is why they are definitely hungry again after being without any food for more than 2 hours. Total passage time of fibrous food throughout the entire intestinal tract can however take two to three days.
To provide horses with this necessary continuous flow of forage without putting on the pounds can be a real challenge, esp. with the so called easy keepers. The easiest way would be to provide hay around the clock, but many horses get obese on this. Ingenious minds have come up with lots of good solutions, from all kinds of different slow feeders to small mesh hay nets. Google “slow feeding hay” and “small mesh hay nets” and you will find a huge amount of information. My personal preference to date are the small mesh hay nets, kept as close to ground level as possible. Beware of feeders that don’t allow for “grazing” height or require a lot of neck contortion from the horse. To keep jaws properly aligned the horse should not chew with elevated head and neck and/or contorted to one side.
This video on youtube gives an excellent visual presentation on the horse’s digestive tract, I very much recommend watching it. http://www.youtube.com/watch?v=8lqk7igz9L4
Foals have undeveloped cecal and colonic digestion as compared to the adult horse. There is very little microbial digestion before three months of age. Therefore, the foal requires a diet low in fiber and easily digested in the fore gut. Foals who are seen eating their mothers manure are thought to be obtaining a bacterial culture necessary for future microbial digestion.
In the mature horse, the sheer numbers and variety of the microbial population in the large intestine gives the horse some protection against diet changes but the system is not fool proof. The large bowel functions best with a nearly steady flow of nutrients, which means constant access to food. Since horses sleep only about 2 hours a day in deep sleep, and another 5 in light sleep (much of that standing and never in one stretch), given a stomach and small intestine transit time of about 6 hours, a horse with constant access to food will have a virtually constant trickle into the cecum. Free roaming horses will eat a variety of vegetation, including bark, tree branches, moss etc. which encourages a wide variety of microorganisms, so even if they encounter young new growth or different vegetation their systems can quite readily adjust. Domesticated horses usually have a much more limited amount of these organisms as they often eat exactly the same hay and grain in the same ratios for months or years, and so are highly susceptible to any abrupt diet change, resulting in colic or even laminitis.
Spring grass after a long winter of only hay all too often is a major contributing cause. Young lush fast-growing plants are low in fiber, can contain 22-25% protein and equally large amounts of highly digestible carbohydrates. The foregut cannot properly digest this volume and parts of the forage end up in the hindgut. The hind gut microbes are not prepared for this sudden switch between different feed qualities and in an attempt to rapidly change the bacterial flora many of the present microbes die off. Death of large numbers of bacteria will, in turn, lead to the release of large amounts of endotoxin from the bacteria. Horses placed abruptly on pasture thus are at high risk for laminitis or even founder due to the sudden shift to a highly digestible feed. Climatic conditions, such as drought or frosts can compound this problem as any stress to the plant results in higher sugar content.
Feeding large amounts of grain without getting the system slowly used to it results in the same scenario. Some people give a horse large amounts of grain before a strenuous event, thinking they supply the horse with more energy. Nothing could be worse for the horse.
Metabolically challenged horses with compromised immune systems are esp. sensitive to the sugars in the grass and some may not have any grass at all. Even 5 minutes can be detrimental for some horses, so when stabilizing an insulin resistant horse, no grass at all is the best approach. Once the horse has been stabilized with correct nutrition, limited grazing may well be possible, esp. on safe pastures. Mature stands of grass that have gone to seed in mid to late summer are the safest condition. However, droughts can quickly change this and dramatically raise sugar levels. As already mentioned, the rapid growth in spring can be a big problem, and fall weather with frosts and lots of sunshine can also wreak havoc.
FEED INTAKE
For maintenance, horses need to consume 2 to 2.5% of their body weight in dry matter daily. However, it has been estimated that horses on pasture 24 hours a day can consume up to 3.3% of their body weight in dry matter; however, this much food without adequate exercise will often lead to obesity. Feed intake needs to be in relation to energy output, and is also dependent on temperature. As horses have a large body surface, they need to produce lots of energy to stay warm. As explained earlier, this heat is created by fermentation of fiber in the hind gut. The colder the temperature, the more energy they have to produce, which means the more fiber they have to ingest. When well below freezing, horses should be fed free choice hay, even when overweight. They cannot utilize the body fat for energy the same way as the fiber source. As grain does not have much fiber, it also is not a good source for heat production.
A word about weight management: while being overweight is just as bad for horses as humans, in order to lose weight, starving is NOT the way to do it. Again, just like with humans. Any organism that is starved tries to make the most out of food the next time it gets supply, so it will take less and less food to put weight back on. But with horses, the roughage requirement of this very long digestive tract complicates things further, like already explained above. The bare minimum of dry matter a horse needs is 1.5% of his body weight in moderate temperature. Anything less than that, and the horse’s digestive tract will suffer. Exercise is the key to weight loss, as is low sugar/low starch forage.
Adequate water intake is also a must in order to keep impaction at bay. It is essential that a horse has always access to clean and fresh water, esp. when only eating hay. So often I see totally murky water tubs, sometimes even with algae growing, and in the winter in our cold climate nothing but thick ice, with maybe a little water beneath. No wonder so many horses colic. In order to keep water clean, I have only a 50 gallon tub for 5 horses so I can easily clean and scrub it, often daily. So often I see 100 gallon tubs for 2 horses, and they hardly ever get cleaned, only topped off. Below freezing, a water heater needs to be installed, or other ways found to keep the water from freezing (good insulation, adding hot water etc.).
NUTRITIONAL REQUIREMENTS
In order to stay alive and retain good health, every living organism has certain nutritional requirements. These have not so much to do with volume of food, but with type and quality. If the required nutrients are not contained within food stuff, just consuming more of it does not deliver the required elements. In human nutrition, we often speak about empty calories from sugar. Sugar is pure carbohydrate and contains no other beneficial nutrients like minerals or vitamins. Similarly, feeding a lot of grain to horses deprives them of very essential nutrients only good quality forage can supply. While grain does have more nutrients than plain sugar, it still is a very incomplete feed for horses.
The National Research Council has released nutrient requirements for many species, incl. horses. http://nrc88.nas.edu/nrh/ . Dr. Kellon has based her research on those guidelines, but has improved on it in many ways by staying current with ongoing research. I will use her recommendations in this article. Thanks to all that accumulated information we have comprehensive knowledge today of what nutrients a horse requires and in what quantities.
Basically, every organism needs to get from its food energy, proteins, minerals and vitamins.
Energy and protein is usually not a problem for the horse if receiving plenty of quality forage. By quality I mean nutritive plants, not just weeds or plants grown on very poor and depleted soil conditions. Green grass and most grass hays have plenty of protein, although it can happen that the content of hay is too low.
With minerals and vitamins, there is no such relative assurance. Mineral content can vary widely, and vitamins in hay suffer from curing and storing. The biggest problem with minerals is that not only the quantity of each mineral is a concern, but the interaction between them as well. Some minerals have to be in a certain ratio to each other, otherwise they compete with each other for uptake and make the organism deficient. Esp. for growing horses, this is a major concern.
While the proper mineral uptake is essential for good health, the horse (like other animals) can make do for a while when conditions are less than adequate. Bones store certain minerals, and the body will go there for reserves when the blood is no longer carrying the ideal balance. As already mentioned, blood as the supplier of all major organs strives to be totally complete and draws nutrients where it can find them. Some minerals like selenium and iodine cannot be stored and need to come from food, however. So most mineral deficiencies are not evident for quite some time, and if the horse finally does exhibit symptoms, the mineral deficiency may be quite considerable.
MINERALS
The major or macro minerals are calcium, phosphorus, magnesium, potassium, sulfur, sodium and chloride, the trace- or micro minerals are iron, copper, zinc, manganese, selenium, iodine and cobalt. This does not mean that macro minerals are more important for bodily functions, only that they occur and are needed in much larger quantities. They are measured in grams, while micro minerals are measured in one thousands of a gram (milligram).
The availability of minerals to the plant and thus to the horse depends on the pH in the soil that grows the forage. Here is an excellent link that illustrates this topic. http://www.extension.org/pages/13064/soil-ph-modification
MACRO MINERALS
Calcium
Calcium (Ca) is probably one of the most well-known minerals in the equine diet. This is due mostly to its interaction with phosphorus (P) in the Ca:P ratio and the big impacts that ratio can have on growing horses (and adult horses too!).
Though Ca has many functions in the equine body, approximately 99% of it is found in bone which is made up of approximately 35% Ca.
The ideal ratio of calcium to phosphorus is between 1.2 and 1.5 parts of calcium to one part of phosphorus, (the ideal ratio with magnesium is 2 parts calcium to 1 part magnesium, a fact that is much less known). Although adult horses can tolerate higher Ca : P ratios, excessive calcium intake has a negative effect on phosphorus absorption, just like high phosphorus reduces calcium absorption. Interestingly, appropriate salt intake increases the absorption of both minerals. This is why it is important to look at the entire diet. An “off the shelf” mineral supplement will likely provide minerals in the appropriate ratios, but can never be expected to compensate for an imbalance elsewhere in the diet. If a forage is excessively high in Ca relative to P a correctly balanced mineral mix will never remedy that.
Calcium deficiency in the growing horse can lead to bone diseases like osteopenia ( crooked long bones and enlarged joints) and metabolic bone disease which is a general term for many bone disorders; in the adult horse it often manifests as high anxiety, muscle problems and poor performance as every cell in the body is dependent on adequate supply.
Phosphorus
Like calcium, phosphorus (P) makes up a large part of a horse's bones, nearly 14% .
However, being a part of bone is not its major role in the equine body. It is extensively involved in other very important functions on the cellular level.
For growing animals it is crucial that the Ca : P ratio is optimal as growing bones require both minerals in certain quantities. Lack of phosphorus can lead to weak bones, malformed bones and poor tooth quality.
Very often, calcium is too high in hays and forage, but in certain parts of the country the same can be true for phosphorus. High calcium can also come from water. So when raising young animals, one would be well advised to test water, soil, forage and hay.
Magnesium
For all that it does, magnesium (Mg) is often not properly recognized in equine nutrition. Magnesium is involved in so many aspects of the structure and function of the body that it's virtually impossible to think of anything that doesn't involve magnesium.
Almost 60% of the Mg in a horse's body is in his skeleton, while another 30% is found in his muscles. The other 10% is found in various areas, including the blood and liver.
Magnesium can only be properly absorbed if it is in the right ratio to calcium. This ratio Mg : Ca is 1 : 2.
One of the most common signs of magnesium deficiency is extreme nervousness. Other symptoms include irritability, hypersensitivity, muscular symptoms from twitching to spasm, with a potential for GI symptoms and heart irregularity when severe. Further symptoms can be gait disturbances, including stilted gait, base wide gait behind, difficulty controlling the hind end when turning and reluctance or inability to canter. For this reason, magnesium deficiency is often misdiagnosed as EPSM, a muscle disease most commonly associated with heavy horse breeds. The magnesium deficient horse is not a happy camper!
Mg toxicity has not been studied in the horse. Too high levels may interfere with calcium uptake, but this has not been proven and it appears that there is little likelihood of toxicity being a problem.
Potassium
Potassium (K) also has important functions throughout the body. It plays a huge role in maintaining acid-base balance and regulates the amount of water that is inside cells. However its biggest job is skeletal muscle excitability. In "excitable cells" (for instance, neurons, which make up nerves), potassium is responsible for exciting the cell. For example, when your horse wants to swish his tail to get rid of a fly, the muscles attached to the tail bone must be excited so that they contract. They are excited by potassium being rushed across cell membranes. So, every time your horse moves a muscle he's using potassium, and of course the heart, being a muscle, does too. It also aids in the regulation of hormones.
Potassium is usually always plentiful in forage, and excess potassium is excreted. The equine kidney is very efficient at removing excess K from the body. When potassium intake is increased, urinary excretion increases, followed by fecal excretion.
However, horses that are exercising heavily may develop a deficiency, especially in hot and humid weather where they sweat more and therefore lose more electrolytes (potassium is a major electrolyte). Up to 10 to 15 liter of fluid can be lost per hour in exercising horses. Horses that are exercising for prolonged periods (for example, an endurance horse) are at particular risk. The administration of IV or oral electrolytes may not be enough to correct the loss from sweat, as these products are higher in sodium than K, while the sweating horse loses more potassium than sodium. However, due to the excess dietary intake that is common, K may not even need to be supplemented at all.
Deficiency of potassium manifests in the nervous system and especially the muscles.
These include irregularities in the heart rhythm, muscle weakness, spasm or actual tying-up, fatigue, slowed to absent intestinal function, nerve irritability (e.g. Thumps), even paralysis.
Sulfur
Like nitrogen, animals, including the horse, have no known requirement for inorganic sulfur. Plants are an intermediate processor between inorganic sulfur and organic sulfur in the form of sulfur containing
amino acids (cystine, cysteine, methionine, taurine). The horse's sulfur requirements are in the form of these sulfur-containing amino acids.
Skin, hooves, hair and collagen (connective tissue, including tendons and ligaments) are rich in sulfur containing amino acids.
A deficiency has never been described in horses, and doesn't appear to be a likely problem in the average horse.
Toxicity also appears to be of little concern, due to the fact that high levels of the mineral would be required to induce a toxic response.
Sodium
Sodium (Na) is essential for absorption of many nutrients, as well as their entry into cells (including glucose). It also is essential for the normal functioning of all nerve and muscle tissue and is the major regulator of water balance in tissues. In addition to “holding” water in the tissues, sodium is what the brain “reads” in determining when to trigger thirst and when to regulate the amount of sodium, and therefore water, the body excretes in the urine. Sodium levels in the brain are read by cells called osmoreceptors, short for osmolality. Osmolality is a measure of the ability to attract and hold water.
Signs of deficiency include decreased skin vitality, abnormal licking of objects (in search of sodium), decreased water intake, slow eating, and eventually loss of appetite. Horses may also have trouble controlling their muscles, and often have an unsteady gait.
Toxicity is of very little worry in the horse, as it is excreted through the urine. However, if adequate water is not available to the horse, it can become a problem as it cannot be secreted properly.
Forage is usually always deficient of Na, except close to salt water sources or in certain soils.
Thankfully, ensuring that the horse gets enough of this all-important mineral is usually as simple as providing salt (NaCl) in loose form or salt blocks free-choice at all times. But not all horses ingest enough this way and may have to be fed supplemental salt, esp. in hot weather.
One significant source of sodium is water that has been through a sodium chloride (salt) softener. Most systems in use in the United States today soften only the hot water supply, or use reverse osmosis, but if your entire water supply is softened, check the sodium in the water. Natural water sources in some areas are naturally high in sodium, including the plains/prairie states – where interestingly the modern horse is believed to have evolved.
Chloride
Chloride ( the Cl part of NaCl) receives very little attention in the equine nutrition literatures, including the NRC, most likely as it usually is plentiful in the diet. The chloride content of the blood and extracellular fluids plays a key role in acid base balance, but chloride does much more than this. Chloride is secreted as stomach acid and chloride channels (“pores”) on cells are involved in a host of reactions that involve maintaining normal pH, fluid volume and electrical conductivity of cells.
Most people know that the Na is for sodium, but many do not realize that the Cl is for chloride. Sodium chloride is common salt, and it is 61% chloride.
Other feedstuffs do contain Cl as well, as listed below:
Grass Hay - 0.92%
Legume Hay - 0.61%
Grass Pasture - 0.58%
Thankfully it is very easy to meet requirements due to the intake of common salt and toxicity and deficiency are of very little concern.
MICRO MINERALS
Micro minerals are needed in much smaller amounts than macro minerals but are no less important for the horse’s overall health. The importance of any of the trace minerals is enough material to fill a book. It's difficult to picture how something the horse requires in less (often MUCH less) than teaspoon amounts can really be that important.
Iron
Iron (Fe) is essential for the horse to be able to transport oxygen throughout his blood. It makes up the center of hemoglobin, which is the oxygen transport molecule in blood.
Iron is also an essential mineral for the transport of oxygen throughout the body, and as such, it is essential that horses receive enough every day.
60-80% of the mineral in a horse's body is found in hemoglobin and myoglobin. Another 20% is stored in the liver, spleen, and other tissues, and the rest is distributed throughout the body in various places.
A moderate deficiency is not a concern for the majority of horses, especially if they have access to soil. Common soil contains a large percentage of iron, and just the dirt and dust in grass or hay can contribute plenty of iron.
If a deficiency were to occur, it would result in anemia. Young foals are more susceptible to anemia than grown horses, though again, it is of little concern since most horses obtain enough of this important mineral.
Except in specific proven deficiency cases, it is suggested that Fe supplements not be given due to the adverse effects outweighing the possible benefits and special caution applies to foals, as any excess is toxic to them.
Iron is quite possibly the most over-supplemented mineral in equine diets. More is never better, and this is particularly true for iron since the horse has no way to actively excrete it. As little as 350 mg of supplemental iron can kill a foal. If iron deficiency is suspected, it should be confirmed by testing serum iron, total iron binding capacity and ferritin levels.
Excess iron has many negative effects, including predisposition to infection, secondary zinc and copper deficiency, predisposition to arthritis and increased risk of tendon/ligament problems, liver disease and altered glucose metabolism – including insulin resistance and overt diabetes. In a self-perpetuating cycle, IR and diabetes also increase iron absorption
The treatment for iron overload in people is blood-letting, periodic blood draws to remove the iron in the serum and contained in the red blood cells. In humans, it is known that regularly giving blood
reduces the risk of developing IR, and lowering the iron burden improves already established IR. In horses, iron build up can be stopped, and levels of ferritin gradually lowered, by instituting a tightly mineral
balanced diet.
Iron toxicity in horses is quite prevalent and often not recognizable by just looking at a horse, but in advanced cases, there are visual clues: dark horses have a reddish sheen on their coat, and mane and tail ends are reddish. Also, chestnut horses lose their rich color and look more like a palomino.
Also, iron, copper and zinc closely interact, and most often an apparent iron overload is not just due to the amount of iron, but is because of lack of copper and zinc,( these two minerals being responsible for coat color). In a healthy horse, iron to copper to zinc ratio can be 10 :1 : 3, but in sick or metabolically challenged horses it should be 4 : 1 : 3, which usually means quite high levels of copper and zinc supplementation. Once enough copper and zinc are supplemented the iron overload can slowly balance itself out. The reason these ratios are so important is that iron competes with copper for uptake by the cell walls. It is sort of like a lottery: when there are 49 black balls in a machine and only 1 white ball, it is quite easy to predict which color will be going into the chute. Zinc and copper have a similar relationship, too much of one can cancel out the other.
Again, while commercial supplements may meet basic requirements in correct ratios, they do not contain enough to compensate for high iron content in the diet, which is quite a common occurrence. Only diet analysis can provide this information.
Copper
Copper (Cu) is used in the creation and maintenance of elastic structures such as connective tissue and other structures. This is especially important in growing horses, as the bone collagen is one of these structures that relies on the presence of Cu to develop correctly.
It is also important in moving stores of iron to areas where they are needed, as well as for the creation of melanin, the substance that gives skin and hair its color.
Another important function of Cu is to help create red blood cells, and lastly, it helps keep the central nervous system running correctly.
Because Cu is associated with connective tissue and bone, a Cu deficiency may cause thinning of the bones, swelling of the joints and possibly even limb deformities. And as it is associated with the production of melanin it can give the coat a bleached and/or reddish and dull appearance.
It appears that horses are fairly tolerant of high Cu concentrations. When horses were given large amounts of Cu orally, no adverse reactions were seen. But of course zinc levels must then be at the appropriate ratio also, otherwise high Cu levels will suppress Zn uptake.
Zinc
Zinc is one of the most common nutritional deficiencies. It performs a host of functions in the body.
Structures on proteins called zinc fingers allow them to bind to DNA. Zinc fingers also influence the folding and structure of proteins. In enzyme systems, zinc is essential for pigment formation, antioxidant function, transport of carbon dioxide in the blood, bone building and remodeling (alkaline phosphatase) and insulin production and release among others! Zinc is also a “messenger”. Release of ionic zinc by cells is one way that cells in the nervous system “talk” to each other. Zinc is also absolutely vital to immune system health.
Severe zinc deficiency in foals is known to cause poor appetite, stunting, skin scaling and baldness. Less dramatic inadequacies in adults could produce a host of very common health issues including poor coat, mouth ulcers, skin flaking, poor hoof quality and ridging, poor fertility, mild anemia (oxidative damage), sub-optimal immunity and predisposition to skin infections.
Like with copper, horses tolerate high levels of Zn, but high intakes can produce toxicity by way of creating a secondary copper deficiency. Zinc intakes between 1000 and 2000 ppm without also
increasing copper intake cause copper deficiency symptoms of joint swelling, lameness, joint effusions and cartilage defects.
Trace minerals must be kept in balance.
Manganese
Manganese (Mn) is essential for correct bone formation because it is a part of chondroitin sulfate. It is also required to activate a number of important enzymes, and is essential in the digestion of carbohydrates and lipids.
Manganese deficiency can result in cartilage and bone problems in growing horses. Low cholesterol and altered glucose metabolism may be seen in adults. These are probably the
functions that depend heavily on manganese.
Manganese is usually in plentiful supply in forage and feeds, so deficiencies are hardly ever reported.
Manganese has a strong affinity for ferritin, the protein that normally keeps ionized iron out of the circulation. Ionized iron is a very strong oxidizing agent (think of the body rusting from the inside out!). Because of the strong affinity for ferritin, manganese actually may worsen iron's toxic effects by reducing the number of available binding sites on ferritin. So again, balance is the key.
Selenium
Selenium (Se) is considered an antioxidant because it prohibits free radicals from damaging the cell membrane. It is commonly found in soil, groundwater, and plants.
For the very tiny amount of Selenium the horse requires, it does an incredible amount of very important work. Researchers are actually just beginning to scratch the surface in understanding the importance of selenium. But probably no other mineral raises such concerns over both low and high intake, and supplementation is still highly controversial.
As a general rule, however, areas with alkaline soils (either natural or as a result of field treatments like heavy liming) will be most likely to have adequate to high selenium levels in the hays and grains grown
on them, while very acid soils inhibit selenium uptake by plants. Even in very selenium adequate locations, feeds grown in close proximity to large cities with high acidifying contaminants may have
low selenium, while hays on heavily limed fields in borderline areas may produce adequate crops.
Selenium is one of the few minerals where testing the horse can give an accurate picture of body selenium status. Because of wide individual variations in how efficiently selenium is absorbed, this may actually be preferable to diet testing. Whole blood selenium is the most accurate, since the red blood cells store considerable amounts of selenium.
Selenium is usually discussed in connection with vitamin E, because they can substitute for each other to some extent. Se is also absorbed better when the system contains adequate amounts of E.
Adequate Se intake is very important for exercising horses. Subtle deficiency effects include muscle soreness and loss of performance; riders and trainers of high performance horses can testify to less muscle pain/cramping, better recovery, better performance with supplemental Se.
Compromised immune function and anemia can also be an indicator. From experience I know that low selenium predisposes the horse for fungus in the skin like rain rot and scratches.
The severe toxicity symptoms of this mineral are the reason why supplementation is so controversial.
Acute selenium overload can be fatal. Clinical signs of acute selenium poisoning include gait abnormalities, garlic or DMSO like breath odor, labored breathing, and muscle tremors.
Chronic overload is more common, however. In both instances, the first symptom is often hair loss, horizontal hoof cracks, followed by foot pain that can progress to sloughing of the entire hoof. It also can cause blindness, abdominal pain, excessive salivation, teeth grating, paralysis, respiratory failure, and death.
Iodine
Iodine (I) is a very unique mineral in the equine diet. It is the only mineral that has only one function in the body, as well as the only mineral that both a deficiency and excess cause the same symptoms! It is an important part of the thyroid hormones thyroxine (T4) and triiodothyronine (T3), the hormones that regulate basal metabolism!!
The two basic malfunctions of the thyroid gland are hypo-thyroidism (the gland is underactive) and hyper-thyroidism (the gland is overactive).
When there is an iodine deficiency, not enough of the thyroid hormones can be produced, thus TSH (Thyroid stimulating hormone) production increases to attempt to increase the production of the hormones. As a result of the TSH increase, the thyroid works harder. Due to the extra work, the thyroid increases in size, and the horse ends up with a condition known as goiter, or enlarged thyroid.
On the other hand, if there is an excess, the extra mineral present inhibits the production of the two hormones, not enough hormones being produced means that TSH production increases. Increased TSH production means a harder working thyroid, which leads to a larger thyroid and yet again, the horse ends up with an enlarged thyroid, or goiter.
What complicates matters is to find out what situation is present. Blood tests are inconclusive as the hormone levels fluctuate during the day, so one sample could be normal, the other way off balance, and no other way is known for horses.
Kelp is often the supplement of choice to raise iodine levels, but some kelps can contain high levels of bromine (which is an iodine antidote) besides the iodine, rendering the iodine ineffective. There also can be sources of bromine in the environment from chemicals like pesticides.
In addition, there are very differing opinions on how much iodine to supplement, and what is the best way. Iodized salt is one way, but the horse needs to consume quite a considerable amount on a daily basis. So if feeding free choice iodized salt it must be under close supervision. Another way is to feed human grade supplements like Iosol or similar. The current intake recommendations for a 1000 lbs. horse are 3.5 mg/day.
One of the main symptoms of an underactive thyroid is obesity, esp. if it persists with limited food intake and lots of exercise. Others are lack of energy and shedding problems. A hyperactive gland can cause weight loss, inability to relax and inability to sweat.
Cobalt
You will see the mineral cobalt (Co) listed on hay analyses and even in the NRC recommended intake charts. Cobalt has no known functions inside the body except as a component of vitamin B12.
Meat eating animals ingest B12 in meats but vegetarians/herbivores have no dietary source of B12. Their B12 comes from synthesis by the intestinal bacteria. According to Dr. Kellon, B12 deficiency has never been documented in a horse. Presumably all equine diets therefore contain adequate cobalt.
There exist other opinions as well, but no good studies are available.
CONCLUSION
If the reader has made it so far, I guess it has become obvious just how important all minerals are, and especially in the correct ratio with each other.
As a result of her yearlong studies, Dr. Kellon recommends the following ratios:
Ca : P 1.2 to 1.5 : 1
Ca : Mg 2 : 1
Fe : Cu : Zn : Mn in totally healthy animals 10 : 1 : 3 : 3
Compromised health 4 : 1 : 3 : 3
She also advises to provide all minerals at at least 150% of the NRC recommendations.
Mineral requirements change with age and performance, therefore no precise amounts can be given here, it would be too extensive. But as an example I will show one of my hay analyses and the calculations of the minerals provided by the hay, and what needs supplementing.
Again, please consider that these are just guidelines. You don't have to get obsessive about giving precisely these. This is not EXACT science, but does give an idea of excess or deficiency.
Also, it can happen that hay has extremely high Mn (like the one below). Then, according to Dr. Kellon, Cu and Zn need to be balanced to the Mn, and the iron will be lower than 4. Again, as long as the horse has access to soil, no supplementation should be needed. If in doubt, do a blood test.
PROTEIN
Protein in the diet is digested down to single amino acids or very short amino acid chains (peptides), then absorbed. From there, proteins are rebuilt according to demand within the body.
The diet provides amino acids that are both essential and nonessential. Nonessential amino acids can also be created in the horse’s body by converting one amino acid into a different one.
Essential amino acids cannot be created in the body and have to be provided by diet.
Amino acids have to be present in certain amounts each to facilitate protein absorption. When an amino acid is not present at required levels, it becomes a limiting amino acid. It is called limiting because if amounts are not adequate, protein synthesis will not be able to proceed normally. To picture how this works, imagine the body trying to make a necessary protein structure by stringing together the different amino acids. Imagine each amino acid as a different colored bead and protein as a string made up of different colored beads in a set formula. If the body runs out of an essential amino acid, the protein cannot be completed.
There may be plenty of other amino acids around but they can't be used because the one necessary to build the chain is missing. This missing amino acid is therefore limiting the body's ability to construct that protein.
Lysine is one of those limiting amino acids that we know of. To date it remains the only essential amino acid where equine requirements have been reasonably well established.
CARBOHYDRATES
The horse’s diet contains lots of carbohydrates. They are differentiated between complex and simple carbs.
Complex carbs are the components that are classified as fiber : cellulose, hemicellulose and lignin. Simple carbs are sugar and starch.
Ideally a horse’s diet is rich in fiber and low in sugar/starch, as mentioned earlier in this article. This is esp. important for IR or metabolically challenged horses.
Most forage has a very high percentage of fiber, while grains have a very high percentage of simple carbs.
FATS
Although the equine diet is very low in fat, fat does play important roles in the body like being part of cell walls and transporting fat soluble vitamins.
Feeding high quantities of fat has become quite a fad lately, so various oils and rice bran have been added to the equine diet, esp. for hard keepers or metabolic horses.
According to Dr. Kellon, this is not a good idea. Although fats are the most energy dense calorie source pound per pound, processing them into useable forms takes multiple steps and energy generation from fats is slow. Also, fat can easily pack on the pounds, quicker than forage.
In addition, experience has shown that it may exacerbate insulin resistance. I know this from experience and can only advise not to add oils or rice bran to the diet of an IR horse or an overweight horse.
What needs to be supplemented are the essential fatty acids that the horse cannot produce himself and so need to come from the diet. Green grass supplies the horse with plenty, but if this is not available another source has to be substituted. Flax seed or chia seed are the best choice.
HAYANALYSIS
This is a typical hay analysis. It does not mention selenium or iodine as we know that the hay grown in this area is definitely deficient in both. Matter of fact, there is so little selenium in the soil and forage that a test cannot detect any.
At this opportunity, I will also discuss the entire analysis, not just the minerals.
As most of the measurements given are either in percent, parts per million of g/mg it is easiest to demonstrate the mineral requirements on a 500 kg horse, (which would be about 1100 lbs).
But DE is only given in pounds, just to confuse matters, and of course g/lb is also given with all minerals. But in general, I find the decimal system easiest to use.
Digestible energy
Calories from a food that are actually available for absorption
A 500 kg horse in moderate exercise needs about 22 Mcal/day. (Taken from NRC charts)
Feeding this hay at 2% body weight (10 kg - 22 lbs) would deliver 17.8 Mcal (22 x 0.81)
To reach the required 22 Mcal, and additional 2.5 kg would need to be fed. Or some other feed may need to be given.
Crude Protein
At 22 lbs/day the above hay would yield 22 x 35.3 = 776.6 g
Formulas for Daily Crude Protein Intake requirement in grams/day for moderate work
Minimum: Body weight (in kg) x 1..4
Average: Body weight x 1.53
Elevated: Body weight x 1.73
Minimum: 500 x 1.4 = 700 grams
Average: 500 x 1.53 = 765 grams
Elevated: 500 x 1.73 = 865 grams
So 10 kg of this hay would deliver adequate protein for average requirements.
Estimated Lysine
Lysine is not actually analyzed. An estimate is given based on published amino acid profiles in various hays. Lysine is an essential limiting amino acid that the body cannot manufacture itself. It needs to come from the diet. Limiting means that a certain amount of it is necessary to help with uptake of other amino acids. If there is not enough lysine, other amino acids cannot be utilized either, leading to protein shortfall in spite of plenty of crude protein.
Formula for lysine is required protein x 0.043
An adult horse 500 kg in moderate work needs about 33 g of Lysine (765 x 0.043). At 10 kg, this hay would fall short by providing only 27 g. Feeding another 2.5 kg would give additional 6.75 g, so this would then meet requirements.
ADF
A measure of slowly fermented fiber fractions, cellulose and lignin. This is the least fermentable fiber fraction. It increases with plant maturity. Higher ADF = lower calorie yield.
NDF
This includes hemicellulose, cellulose and lignin. Hemicellulose is the most easily fermented fiber fraction.
Fiber fractions are what give the plant cell walls rigidity. They are all insoluble.
WSC
These are carbohydrate fractions that can be extracted in water.
This includes digestible sugars such as fructose, glucose and sucrose, indigestible (by the horse) plant sugars, and some fructan. How much fructan is extracted will depend on the duration and temperature of the extraction as well as the complexity of the fructan molecule.
ADF. NDF and WSC values are not important for us to consider when building the diet. Neither is RFV. This number was really developed for use with cattle and has little practical value in a horse diet.
ESC
This fraction is sugars only. This is an extremely important number for us to know as high sugar content is detrimental for metabolic horses. Sugar and starch values together should be below 10%,
with starch being by far the lower number. This particular hay is very suitable, sugar being 5.4, and starch being 0.6, for a total of 6.
Starch
An important number to know for metabolic horses, see under ESC. The lower the starch the better.
NFC
This includes all carbohydrates that are not part of the cell wall –
sugars, starch, pectin, beta-glucans and fructans. This includes the digestible and easily fermentable
carbohydrates.
This number we also don’t have to concern with. (although some nutritionists may say otherwise)
Calcium
Requ.: 500 kg moderate work 35 g 10 kg hay provide 45 g excess 10 g
Phosphorus
Requ,: 500 kg moderate work 21 g 10 kg hay provide 18 g deficient 3 g
Magnesium
Requ.: 500 kg moderate work 12 g 10 kg hay provide 15 g excess 3 g
So if not considering ratios, one would think that only P needs supplementing.
However,
Existing ratio Ca : P 2.5 to 1
Ca : Mg 3 : 1
P is 3 g deficient and the ratio should be 1.5 to 1
As it is for an adult horse and the horse is fed more of that hay to meet energy requirements, this would not be of concern.
For a growing horse the P would have to be adjusted to a ratio of Ca:P of 1.5:1.
P would have to be 30, which means 12 g of P would need supplementing.
Mg should definitely be supplemented by 7 g or relative to final hay consumption to achieve the proper ratio with Ca.
Potassium
Requ.: 500 kg moderate work 32 g 10 kg hay provide 124 g
Sodium
Requ.: 500 kg moderate work 18 g 10 kg of hay provide 0.5 g deficient 17.5 g
Iron
Requ.: 500 kg moderate work 450 mg 10 kg of hay provide 700 mg excess 250 mg
Zinc
Requ.: 500 kg moderate work 450 mg 10 kg of hay provide 200 mg deficient 250 mg
Copper
Requ.: 500 kg moderate work 112 mg 10 kg of hay provide 60 mg deficient 52 mg
Manganese
Requ.: 500 kg moderate work 450 mg 10 kg of hay provide 1070 mg excess 620 mg
Molybdenum
No values available
With this hay, it is important to get the Mn in ratio with Cu and Zn. This will result in a relatively low iron, but according to Dr. K. we never have to worry about iron with horses who have access to soil.
700 : 356 : 1070 : 1070
So we would have to add 296 mg of copper and 870 mg of zinc.
Most often, iron is much higher than in the hay above and manganese lower. But this hay demonstrates how important it is to find out what is in it. This high manganese would totally cancel out copper and zinc which are already deficient even without high Mn.
Again, all this is not totally reliable science as the lab may have some errors, horses may eat more or less or browse on things we can’t measure, the samples we took may not be totally representative of the whole load, etc., but it is a whole lot more beneficial than not supplementing or buying some premix that may actually worsen the situation.
The Equine Cushings list is about 10000 members strong, and great results have been achieved with IR and Cushings horses, implementing this method.
SUMMARY ON NECESSARY SUPPLEMENTS FOR THIS HAY
In addition to the minerals, we have to think of the Omega 3 fatty acids. Horses on pasture get enough of those, but horses only getting hay need an additional source.
Flaxseed is a good choice, but needs to be ground up for good absorption. One can buy stabilized ground flax or can grind whole flax daily in needed amounts.
The 500 kg horse would need about 4 oz.
Horses on hay only will also need Vit. E (more on this below) at an amount of at least 1000 IU/1000 lb. Metabolic horses need more. The easiest way to supplement is with human oil based gel capsules.
So our list for a 500 kg adult looks like this:
Mg 7g (this is elemental magnesium. If using Mg Oxide, which is 54% of elemental Mg, one would need to add 13 g of MgOxide – 1 g of MgO = 0.54 g elemental Mg)
Cu 296 mg
Zn 870 mg
Se 2 mg
Iodine 3.5 mg
Flaxseed 4 oz
Vitamin E 1200 IU (IR or Cushings horses double the amount)
While the total calculations are certainly quite involved and may seem overwhelming at first, it is amazing how little one needs to supplement to balance the hay.
Compare this to premixed supplements and you will find that there is a huge difference. Not only is this way a lot more precise and helpful for the horse, but also much less expensive in the end.
An additional note: minerals can come from lots of different sources like carbonates, oxides, sulfates etc. Each of those has different elemental mineral content so it is very important to find out about this.
Just getting “copper” for supplementing is not of much help, one always needs to know how much of the elemental mineral is really in there.
Also, if you follow my above calculations and are doing them with the g/lb or mg/lb column, you may end up with slightly different numbers. This is due to the conversion error of kg to lb.
VITAMINS
Vitamins are differentiated between fat soluble and water soluble. Fat soluble means that they can be stored in body fat and the body can draw from stores when diet is deficient, but toxicity can also occur quicker.
Water soluble vitamins get flushed out with urine and deficiencies can occur a lot quicker, but toxicities are less likely.
However, true vitamin deficiencies in horses are rare and many of the vitamins a horse needs are produced within its digestive system. According to Dr. Kellon, Vit. E is the only vitamin that needs supplementing much of the time.
Fat Soluble Vitamins
Vitamin A
This vitamin has many important roles in the body, amongst others it is needed for night vision, immune function and reproduction.
Most any premixed horse supplement contains Vit. A, it is quite possibly the most over-supplemented vitamin.
Horses ingest vitamin A from their forage as beta-carotene. Beta-carotene is broken down in the small intestine and liver of the horse to be converted into A.
Horses getting even minimal amounts of green forage are unlikely to require supplemental vitamin A. However, if your forage/hay is not at least a bit green, levels are most likely too low.
In other species, and likely the horse as well, intestinal conversion of beta-carotene to active retinol is down regulated by the presence of retinol, which protects the horse from over-dosage due to carotene intake, but toxicity caused by over-supplementation of vitamin A itself, not beta-carotene, is still possible.
Deficiencies are rarely reported, but night blindness, one of the symptoms, does happen occasionally.
Toxicity through supplementation others than beta-carotene can be a serious problem, however. It can result in fragile bones, fetus deformities and other problems.
A safe way of supplementing is through some grass, or carrots. An 8” carrot can provide 8500 IU of vitamin A. The dietary daily minimum intake for a mature horse is about 15000 IU.
Vitamin D
Vitamin D, as one of the fat soluble vitamins can be stored in the body. Its main role in the body is to keep the calcium levels in the blood constant. D most often works in the digestive tract but it also helps to release calcium from the bones when needed or to be stored in the bones. This is why most calcium supplements on the market also contain Vitamin D.
In the horse diet, D is relatively low. The only place it is really found naturally is sun-cured alfalfa. However, because all normal, healthy horses (and humans for that matter) synthesize D in their body through exposure to sunlight, deficiency is very rare.
The only time there could be a problem is if the body cannot synthesize it, or the horse is deprived of sunlight.
Vitamin D deficiency is rarely reported. If it happens, Rickets or soft-bone disease is the most common symptom.
Over-supplementing can be very dangerous, though. The main symptoms of vitamin D toxicity are calcification of the aorta and other soft tissues, sometimes hyper-calcemia and death. Upper safe limit of intake is 44 IU/kg of bodyweight.
Vitamin E
Its primary function in the horse's body is as an anti-oxidant. Being fat-soluble, it can easily penetrate cell membranes (which are made up of fat, or lipids) and serves as one of the main antioxidants that protects these membranes. Amounts of E in the horse's diet vary considerably. The main source of it is forage. However, when talking about forages (and therefore naturally occurring sources of E) content declines the longer the forage is stored.
The content also varies based on how mature the forage was at harvest -- older forages have less E activity than younger plants. Grains have a lower content of E than forages. And again, the amount of E found in any given grain varies depending on harvest conditions. To make up for all this variation, most feed companies fortify their feeds with extra E, and as already mentioned above, when a horse does not get plenty of grass, supplementing really is a must.
Vitamin E deficiency can cause muscular dystrophy, a degenerative disease that affects the heart and skeletal muscles of foals under a year of age and may also cause white muscle disease. However, the available studies also point to selenium deficiencies being a major cause of the latter. E supplementation is used, along with selenium supplementation, to treat the disease. Equine Motor Neuron Disease can occur after prolonged E deficiency.
Vitamin E toxicity is not a concern in horses, even with large amounts of supplementation. The upper safe dietary limit, which has not been determined specifically in horses, is set at 1,000 IU per kg of dry matter.
Vitamin K
Vitamin K has one major, and very important, role in the horse's body. Through a complex process it helps with blood clotting. The Gla-proteins (which are part of that complex process) that are made from K are also important in bone metabolism and heart health.
Similar to other vitamins, the best source of K in the horse's diet is his forage.
Dietary requirements for K have not been determined in the horse, but most horses easily obtain all of the K they need from their diet.
Vit. K deficiencies have never been reported in horses, but the major symptom would be problems with blood clotting. Toxicity from dietary intake also has never been reported.
Water Soluble Vitamins
These vitamins include all the B-vitamins and Vit. C
Vitamin C
The main function of Vitamin C is as an anti-oxidant. This means that it works to prevent oxidation, or free-radicals destroying cells.
The horse is able to synthesize C from glucose. Based on a number of studies, it is currently assumed that the horse meets his entire C need by manufacturing it in his own body, meaning he does not need an outside vitamin C source.
For this reason, both, deficiency and toxicity, are of little concern to the horse owner.
Dr. Kellon does recommend some supplementation in horses that have been severely stressed by disease.
B Vitamins
Severe deficiency states have not been found for any of the B vitamins. In addition to diet, all Bs are synthesized at least to some extent by the intestinal microorganisms.
But supplementing individual B vitamins can be helpful in certain situations.
Vitamin B 1 (Thiamine)
Vit. B 1 is very important for carbohydrate digestion. Its functions are very technical and I will not go into them deeper.
Some studies suggest that hard working horses benefit from supplementation.
The highest natural sources are grains, brans, cereal grain byproducts, and most of all brewers yeast.
Deficiencies are very rare as horses can synthesize what they need.
The most classical symptom of thiamin deficiency is beriberi. Beriberi is a nasty disease of the nervous system. Complications often affect the heart, nervous system, muscles, and digestive system. Symptoms of beriberi include pain in the limbs, edema (swelling of the body), and severe lethargy.
Toxicity has never been reported.
Vitamin B 2 (Riboflavin)
Vitamin B 2 is a critical cofactor in enzymes (flavoenzymes) involved in oxidation/reduction actions involving the metabolism of fats, proteins and carbohydrates.
B2 deficiency has never been reported and toxicity is also of little concern.
Vitamin B 3 (Niacin)
It is involved in numerous oxidation-reduction cycles throughout the body. Additionally, one of the co-enzymes it creates is essential in DNA processing, cell differentiation, and calcium mobilization from cells.
Neither deficiency nor toxicity has been reported.
Biotin
Biotin is a cofactor for enzyme systems involved in gluconeogenesis, fatty acid and amino acid metabolism. In people it is involved in insulin sensitivity and seems to be helpful for horses as well.
No NRC Recommendations are established and no deficiency or toxicity has been reported.
Interestingly enough, a symptom of biotin deficiency in people is burning feet. In horses, biotin is commonly used to enhance hoof growth and improve hoof integrity, at doses of 10+ mg/day.
Folic Acid
Folic acid is the synthetic version of Folate, the naturally occurring B vitamin.
It is involved in reactions necessary for the creation of DNA as well as methionine (an important essential amino acid).
Because both DNA and methionine are needed in large quantities for cell growth like fetal growth or tissue repair after injury, it is vital for tissues in these states.
As with other B vitamins, there is limited information about folate and folic acid in the horse. Horses that are on pasture have a higher serum concentration of folate than those that are eating hay, suggesting that fresh forage has a higher concentration than preserved feeds.
It also appears that folate can be synthesized by the microorganisms in the horse's digestive tract.
Vitamin B 6
B6 is a part of most of the enzymes that aid in the metabolism of fats, carbohydrates, and proteins. However, B6 is found in high quantities in most of the feeds that the typical horse eats. As a result, there has never been a reported deficiency in horses. Neither has toxicity.
Vitamin B 12
B12 is involved in carbohydrate and fat metabolism, as well as protein synthesis. It is also involved in a number of enzyme systems (quite complicated).
B12 is not available in plant matter but is synthesized by the microorganisms in the horse's digestive tract. Synthesis of B12 is one of the reasons that the cecum is so important to horses. This process by the microorganisms requires cobalt, one of the trace minerals.
Neither B12 deficiency or toxicity has ever been reported in horses.
Pantothenic Acid
Pantothenic acid is found in numerous places in the body. It is part of co-enzyme A, which is a very important complex that is a crucial part in metabolic pathways involving:
Pretty much anything the horse's body does is going to involve pantothenic acid to some degree, like creating new blood cells, walking, digesting etc..
It is found in significant quantities in most parts of the horse's diet and the horse can also synthesize it himself.
No deficiency or toxicity has ever been reported in horses.
Conclusion about Vitamin Supplementation
Vitamin E is the only vitamin that truly needs frequent supplementing. IR (insulin resistant) horses have elevated levels of inflammatory cytokines and high oxidative stress, and in those conditions this important antioxidant is always deficient. Dr. Kellon recommends to routinely use 1000 IU/day per 500 pounds of body weight, double the normal amount. As mentioned earlier, healthy horses being only fed hay also benefit greatly from supplementation.
If hay looks bleached or is known to be older than 1 year, moderate supplementation with vitamin A at 1500 IU/100 kg, and vitamin D, 300 IU/100 kg may be indicated. If hay is 18 months or older, these amounts can be doubled. Supplying A as beta carotene is always the best way, and if the horse is exposed to sun a lot, D does not need supplementing either.
B vitamin supplementation is not likely to be necessary in horses with normal GI tract function. However, biotin has been shown to have a beneficial effect on insulin signaling in other species and on hoof health in horses. 10 to 20 mg/day /1000 lbs is reasonable.
Folic acid is important for support of nitric oxide production to keep blood vessels dilated. 100 mg is a reasonable amount to supplement. However, horses may not absorb folic acid supplements well. One can also use 1 to 2 oz/day of red beet powder as a folate source.
Vitamin C is an important antioxidant but also increases iron absorption, so very much a double edged sword. If the horse is known to be iron overloaded, especially if the diet has not been carefully balanced, one should avoid it. Older horses or horses with severe illness do have decreased vitamin C levels which might otherwise make at least low dose supplementation advisable (low being under 1000 mg/day), but this must be weighed against iron, particularly since C does not have any direct beneficial effect on IR or vascular health.
Final thoughts:
As I said at the beginning, the above is a highly concentrated overview of equine nutrition, it makes no claims of being fully accurate or complete. Besides, lots of different opinions can be found when surfing the net and in the end everybody needs to follow their own preference. Like with anything else in life, nothing is easy and nutrition certainly is one of the harder subjects to truly comprehend. The more I learn about it, the more confused I often become and the more I realize how little we actually do KNOW about it. But I do know that following the above, many, many horses have made tremendous improvements and at this point, to me, this is the best standard we have.
This is a very good link to read up more on the subject. http://www.gettyequinenutrition.com/
http://ecirhorse.com/# relates important information about the IR and Cushings horse, and if you have a horse like that I would recommend joining Dr. Kellon’s Equine Cushings yahoo group, and of course some or all of her courses.
I am glad to answer questions within my range of knowledge, and for dietary help you can contact a specialist from the list below
http://www.desertequinebalance.com/balancing/the-team
Cheryl Kirkus <shabbonawoman@yahoo.com> Hinckley, Illinois
Carol Layton <carol.layton@gmail.com>,
Valeree Smith <shumist@msn.com>,
Claire C. Cox <shotgun.ranch@cox.net > Waddell, Arizona