Simply put, a vitamin is an organic chemical, neccessary for certain bodily functions. Vitamins can be classified as essential or non-essential depending on whether or not the body, or it's resident bacteria, can synthesize them out of other elements. Essential vitamins can not be synthesized, and must be provided in adequate ammounts by the diet.
Vitamins are also either fat soluble or water soluble. Fat soluble vitamins are stored in body fat or organs and can accumulate to hazardous or even toxic levels over time. Water soluble vitamins are not stored in the body and must be constantly replaced. However, any excess is excreted by the kidneys, so excessive dosage is rarely harmful.
Let's look at each individual vitamin, and see what it does for the body, how much your horse needs, which feeds are good sources, and what are the symptoms of deficiency or excess.
The horse creates it's vitamin A from beta-carotene, which is found in green forage and green and yellow vegetables. Growning pasture and alfalfa hay are the best sources for your horse. In fact, six weeks on green pasture can allow the horse to store up enough vitamin in his liver to last for six months. Hay in storage begins to lose beta carotene. In fact, it can lose almost 10% per month, so year old hay has lost over 90% of it's beta carotene.
A mature horse requires 22,000 International Units (IU)of vitamin A per day. Two pounds of fresh grass will supply over 27,00 IU, while two pounds of good hay contains 8,000 to 160,000 IU. In other words, most horses get plenty.
Deficiency, while rare, can happen in foals, who can be born deficient, since Vit A does not pass through the placenta well. These foals may be weak, and slow growing. They may also have teary eyes and suffer night blindnes.
Vitamin A toxicity has never been documented through hay or pasture alone. the toxic level excedes 2,200,000 IU. The most common cause of excess is well meaning owners oversupplementing. Symptoms of excess include a dull hair coat, sloughing skin, and fragile bones. Liver and kidney function will be impaired as well.
B1 is produced by the bacteria in the horses intestine, but they do not create enough for the horse's systems, so he must look elsewhere too. Grass and legumes, as well as cereal grains contain plenty of B1, however storage takes it's toll here too. After one year, hay contains only 5% of it's original B1. Heat processing of feed removes B1 and removing the husks removes all of theB1 found in those grains. Pasture, fresh hay, and whole grains will supply the horse very well.
The minimum recomended ammount of B1 is 3 milligrams per kilogram of feed daily. This is easily supplied by a normal diet.
Deficiency symptoms include a dull coat, nervousness, loss of appetite, lethargy and ataxia (incoordination or staggering). Deficiency is usually the result of intestinal disease or parasites interfering with digestion or absorption. Certain plants also interfere with the absorption of B1. Those to watch for include: bracken fern, horsetail, and yellow star thistle.
toxicosis is nearly always the result of too much injected supplement in an attempt to enhance performance. Symptoms include restlessness, labored breathing, and convulsions. Horses ODing on B1 are also temporarily excitable.
B2 is created by the intestinal bacteria, and is also common in grass and hay.
The horse needs less than 2 milligrams per kilogram of feed daily, which is easily supplied by a normal diet.
At one time it was thought that a deficiency caused Moon Blindness (Recurrant Uveitis) but this has since been disproven.
Neither toxicosis or deficiency is much of a problem in horses.
B6 is produced by the body and is also common in plants. It can be converted into a usable form only in the presence of niacin and riboflavin (B2)
Since the body produces it, B6 is not commonly supplemented, nor do deficiencies appear.
The only known source of B12 is single celled organisms. It is not found in plants.
B12 is produced by microbes in the digestive tract in sufficient ammount to meet the needs of the horse.
Many race horse trainers give Vitamin B12 injections to improve performance, but there is no verifiable evidence that this does anything.
Choline. This B is neccessary for transmitting nervous impulses between neurons. It is also a component of cell membranes.
Choline is produced in the liver of the horse in sufficient quantities for it's needs.
At one time, it was believed that choline could be used to treat COPD (heaves) but research showed no benefits.
Folacin (Folic Acid). Folic Acid is used by the horse to form red blood cells. It may have a role in preventing birth defects. This is being studied currently.
Grass is one of the richest sources of Folic Acid, therefore few horse owners need to wory about it. It is, however, usually included in suppliments designed for pregnant mares.
Niacin. The horse uses Niacin to help regulate his metabolism.
This B occurs naturally in all living tissue. It is produced by the intestinal tract, and also by the amino acid tryptophan.
Pantothenic Acid. This vitamin is used in general metabolic functions.
It is produced by intestinal bacteria and is also present in both forage and grains.
No dietary levels of Pantothenic Acid have been determined for horses.
While not pervalent in the horse's normal diet, vitamin C is created in the horse's liver out of glucose in quite adequate amounts.
In addition, Ascorbic Acid is poorly absorbed by the equine digestive tract, making supplimentation of questionable value.
Vitamin D3 is synthesized by the body of the horse when ultraviolet rays combine with a form of cholesterol found naturally in the skin. Vitamin D2 is found in the dried leaves of plants that have been exposed to sunlight. The horse uses these interchangably.
There are no specific requirements established for vitamin D, since most horses are exposed to sunlight, and eat hay. Vitamin D does diminish in stored hay, however, and year old hay only contains aobut 39% of it's original vitamin D.
Deficiencies are very rare, but they could manifest in rickets-like symptoms and loss of bone density.
Excess vitamin D can cause calcifications of the heart or other soft tissues so supplementation is rarely a good idea.
Found in growning forage, the best sources of vitamin E are alfalfa, timothy, meadow fescue, and kentucky bluegrass. (Kentucky bluegrass is a po;ular lawn grass). The vitamin content goes down quickly as the forage dries, so hay and grain are not good sources. Horses on pasture recieve more than enough, but horses fed only hay all year around may need more.
the average horse requires at least 50 IU per kilogram of feed per day. Horses which are growning, reproducing, or working very hard should have more, about 80 to 100 IU per kilogram of feed per day.
Deficiencies can cause various neuromuscular diseases such as Equine Degenerative Myeloencephalopathy (where the brain and spinal cord degenerate).
Vitamin E does not appear to be toxic, however, an excess can interfere with the utilization of other fat soluble vitamins, therefore the suggested maximum is 37,500 IU per day.
Biotin is mainly synthesized by bacteria in the horse's intestinal tract. The small amounts found in plants are not in a form available to horses.
As a rule, horses create all the biotin that they need. No naturally occuring deficiency has ever been recorded. Laboratory induced signs of deficiency include slowed growth, flaky skin and anemia.
Biotin toxicity in horses has never been reported. The recomended dose for improving hoof quality is 10 to 20 milligrams per day. There is no point in exceding this dosage, which is harmless.
Horses find vitamin K1 in the grass and hay that they eat. Bacteria in the intesting produce vitamin K2. K3 is the synthetic form produced by humans for supplementation. The horse can use any of these forms.
There are no precise minimum daily requirements of vitamin K established, but experts estimate that horses need less then 1/2 milligram per kilogram of feed per day. This amount is readily available in all normal diets. It can also be easily synthesized by the horse.
Deficiencies may occur during a gastrointestinal upset when the bacteria are unable to synthesize the vitamin and the body cannot obsorb it properly. Compromised liver function can also cause a deficiency. Anticoagulant drugs like warfarin can cause a deficiency, as can eating a variety of mold sometimes found on sweet clover. Foals are occasionaly born deficient in vitamin K simply because they have not had time to produce it in their intestines. An injuction of K3 is the perfered method of supplementation.
Natural toxicity of vitamin K has never been repported. If K3 has been given when a horse is not deficient, the symptoms can include renal (kidney) failure and laminitis. Toxicity is such that death can occur within 12 hours.
In this case, Mom was wrong. Tell your horse"Eat a healthy diet!" rather than "Take your vitamins!'.
