When it comes to horse health and nutrition, geography can play more of a part than most would think. With horses achieving a significant portion of their diet through grazing, where they graze can make a big difference. And most California horses are at a distinct disadvantage when it comes to the nutrients—especially vitamin E—they could be getting from grazing.
Vitamin E is an essential nutrient for horses and one that can easily be provided with access to a lush green pasture in which to graze. Grass is an abundant source of vitamin E, but most California horses don’t have this luxury. Vitamin E from grass can only be found in fresh grass. The nutrient levels decrease, and eventually are lost, as soon as the grass is harvested and stored, so cut hay is not an option.
Much of California has a hot, dry climate with little rain. Some desert areas of the state see less than five inches of rain per year, and the more populated centers—the Southern California coastal areas and the Central Valley—receive less than 20 inches—well below the national average. With this lack of rain comes lack of green pastures for horses to graze. Therefore, these horses are not getting the proper amount of vitamin E naturally, and if not supplemented, that deficiency could have dire consequences.
Consequences of Deficiency In short, vitamin E helps a horse’s muscles and nerves function properly. The biological antioxidant helps maintain normal neuromuscular function, and a lack of it can lead to diseases such as nutritional myodegeneration in conjunction with selenium deficiency, equine neuroaxonal dystrophy/equine degenerative myeloencephalopathy (eNAD/EDM), vitamin E deficient myopathy (VEM) and equine motor neuron disease (EMND).
These diseases can be extremely debilitating to horses, if not fatal. EMND manifests in horses similar to amyotrophic lateral sclerosis (aka Lou Gehrig’s disease) in humans, ultimately wasting away the muscles due to lack of nourishment. Horses with eNAD can have gait abnormalities and lose all limb control, while EDM escalates those conditions, resulting in a more severe incoordination.
The Center for Equine Health (CEH) is studying vitamin E deficiency—not only the effects it has on horses, but also potential correlations it may have with humans. Research reveals a number of similarities in how vitamin E deficient neurodegeneration takes place in the equine and human systems. CEH Director Dr. Carrie Finno hopes further funding will allow her team to expand on how vitamin E deficiency contributes to neurodegenerative diseases across species.
Supplementation Since there is no effective treatment for most of the diseases vitamin E deficiency can cause, it is imperative that they be prevented from happening in the first place. If horses are not able to access fresh pastures to graze in, vitamin E must be supplemented in their diet. All vitamin E supplements consist of alpha-tocopherol because alpha-tocopherol is the most biologically available and well researched isoform of vitamin E.
The National Research Council (NRC) recommends a daily vitamin E supplement to be 1-2 international units (IU)/ kilogram of the horse’s body weight. So for a 1,000-pound horse, 450-900 IU of supplement would be necessary daily.
“It’s important to remember that not all horses with vitamin E deficiencies will exhibit clinical signs,” said Finno. “And we want to prevent those clinical signs from happening anyway, so we don’t want to wait around until we are certain of a vitamin E deficiency before supplementing their diets. Unless your horse is on a yearround green pasture, he or she requires supplementation.”
However, Finno stresses the importance of testing blood vitamin E levels before initiating a supplementation program.
“Some horses may require higher doses of supplementation than others, and it is difficult to tailor their dosing without a baseline vitamin E level,” said Finno. “Healthy grazing horses maintain a blood vitamin E level between 3-4 µg/mL, so that should be our target.”
Historically, there was little concern associated with giving too much vitamin E. This was mainly due to the fact that most vitamin E supplements were not very well absorbed in the horse and the NRC levels were based on these synthetic vitamin E supplements. With newer formulations, however, excessive supplementation can occur.
“Previous studies have shown that detrimental effects may not occur until supplementation reaches 10-20 times the recommended amount,” Finno said. “However, these studies were performed using less bioavailable vitamin E supplements (see below). High dosages can lead to bleeding disorders. With the newer supplement formulations, it is critical to repeatedly check blood vitamin E levels so as to not exceed the recommended range.”
Not all vitamin E supplements are created equally. The first generation of supplements were termed synthetic vitamin E, in that they contained alpha-tocopherol, the main antioxidant component of vitamin E, in all of its different chemical configurations. Later research demonstrated that only the “natural” form of vitamin E, or the one containing only one particular highly bioavailable configuration, was highly effective at increasing vitamin E levels in the blood of horses. Since then, additional alcohol-based vitamin E supplements, termed “water-dispersible,” have been developed for use in horses. These are the most effective of all supplements in that the water-dispersible formulation is readily absorbed and the natural vitamin E quickly increases blood and tissue levels in most horses.
Horses in different conditions and different stages of life may require varying levels of supplementation. Additionally, dosing is based on the type of vitamin E formula used (synthetic powder/pellet, “natural” powder/pellet or “natural” waterdispersible). After assessing baseline blood concentrations and identifying deficiencies, pregnant mares should be given 5,000 IU/day of the natural water-dispersible vitamin E and foals should receive 500 IU/day (i.e. 10 IU/kg as the foal grows) of the same product as soon as the foal is born to decrease the risk of eNAD. Blood levels should be checked frequently to ensure that they remain in the normal range.
Finno encourages all horse owners to discuss with their veterinarian what level would be best for their horse before implementing any supplements into their horse’s diet.
Courtesy of UC Davis School Of Veterinary Medicine