The National Research Council (NRC) estimates that a horse needs a minimum of 50 international units (IU) per kilogram of feed. Researchers have increased this level to 80 IU/kg of feed for broodmares, lactating mares, growing and working horses.

Studies have shown that broodmares fed even higher levels of vitamin E (160 IU per kg/feed) had higher serum levels of IgG which indicates that they may have had a more enhanced immune system. It was also found that the suckling foals of these mares also had higher IgG levels than foals of mares fed 80 IU/kg feed.

IgG is an acromim for immunogloblins. The higher the IgG level the more passive transfer of antibodies that a foal receives through its dam’s colostrum and the greater the ability of the foal to stay healthy.

This link between Vitamin E and the immune system is highly significant to a new born foal. Vitamin E does not transfer across the placenta to the unborn foal so all foals are born vitamin E deficient. On the other hand, vitamin E’s partner, selenium, does cross the placenta. That is, as long as the broodmare is fed a diet that has the proper levels of selenium.

Mares on good diets pass high levels Vitamin E and selenium along with the IgG factors in their colostrum to their foals. Once the colostrum clears, Vitamin E and selenium continue to be important components of mare’s milk. A breakdown in this system either due to a Nature design flaw or a poor diet is one of the reasons that vitamin E (and selenium) is implicated in several conditions that affect newborns.

In the article on selenium it was mentioned that a selenium deficiency plays a role in White Muscle Disease. A severe Vitamin E deficiency is also a contributing factor in this condition.

Vitamin E has been implicated in Equine Degenerative Myloencephalopathy (EDM). Equine Degenerative Myloencephalopathy (EDM) is a degenerative disease of the spinal cord and brain stem that is often referred to as “wobbles” or the “wobbler syndrome”. Actually, however, only 1/3 of the cases of horses with wobbles are the result of EDM.

EDM can affects horses of any age but it is most commonly seen affecting foals from 1-14 months of age. Horses with EDM have an abnormal gait which prevents them moving correctly over the ground.

Research has shown that there are many factors which predispose a horse to EDM. Some of them are exposure to pyrethrum insecticides, creosote and oil-based wood preservatives, a genetic factor and a Vitamin E deficiency.

At this point, the exact role that Vitamin E plays in this syndrome has not been completely identified. Some researchers have found Vitamin E levels to be very low in horses experiencing the beginning symptoms of EDM. Others have reported that long-term Vitamin E supplementation is instrumental in the treatment of this condition.

These finding also have validity in horses that have a genetic link to EDM. In a study, 8 out of 9 horses sired by an EDM stallion were afflicted with this condition. Massive doses of Vitamin E were effective in preventions and treatment of this condition.

As a powerful antioxidant, Vitamin E is also a major player in the reduction of free radical formation in the muscles during exercise. Several studies focusing on this relationship led to the suggestion that horses in training and racing receive higher levels of Vitamin E. Saastamoninen (2000 Proceedings KER Equine Conference for Feed Manufacturers.) recommended this amount to be between 1500 and 2500 IU for an 1100 lb horse. Other field studies indicate an increase in performance in horses taking 1000 mg/day.

In 1990, the relationship between Vitamin E and performance was further supported by the identification of a Lou-Gehrig type disease in horses which is referred to as Equine Motor Neuron Disease. EMND affects horses over 2 years of age and associated with and likely caused by prolonged vitamin E deficiency.

EMND affects the nerves that control the muscles in the rear end of the horses. The symptom of this degeneration is trembling, constant shifting of weight between the rear lets, excessive laying down, weight loss leading to muscle wasting.

EMND is a devastating disease resulting in either death of the affected horse or chronic debilitation. In almost all cases, horses developing EMND have had minimal or no pasture exposure for at least 18 months.

Growing forages are the primary source of Vitamin E for the horse with alfalfa, timothy and bluegrass leading the list. At the right stage of growth, these forages can provide the horse with 80IU of vitamin E per kg/feed – the number which is currently recommendation by many researchers.

However, the moment that the forage is cut and transformed into hay these values rapidly decrease. Stored hay might lose up to 50% of its vitamin E the first month.

Vitamin E supplemention is becoming a necessity as more horses are being housed with limited access to growing pasture. The effectiveness of this supplementation is determined by several factors.

Vitamin E occurs in several form. The d-forms of the vitamin are more effective than the dl-forms. Natural Vitamin E is more effective than the synthetic forms. Vitamin E is more effective when fed with grain than when given as an oral past or by stomach tube. This may relate to the fact that amount of unsaturated fat in the diet also effects the action of vitamin E.

Supplementation and the fact that a horse can store excess Vitamin E in its body can help to prevent a horse from slipping into these debilitating conditions. However, for the last 50 million years, horses have evolved to survive on the nutrients in growing plants. It would be wise for management techniques to include time for horses to graze on their natural food.

copyright, Dr. Jim and Lynda McCall