Why Your Horse Needs Vitamin E

Higher levels of vitamin E may also be recommended for horses with certain health issues. “The categories that the NRC does not touch on, but which we have anecdotal evidence and research looking at, are guidelines for disease-state horses—horses with allergies, tying up, metabolic syndrome, or those that are suffering from or recovering from illness,” says Cubitt. “In horses with allergies, we know that potent antioxidants are effective. One guideline that has been suggested is about 5,000 IU per day. Horses who tie up and have muscle problems can also benefit from 5,000 IU per day. Horses with metabolic syndrome, insulin0 resistance and laminitis should also receive that higher level. Horses recovering from surgery, illness or stress may need 1,500 to 5,000 IU per day, depending on the severity of the illness/stress.”

Given that vitamin E is stored in fat, it’s not surprising that severely underweight horses may also have deficiencies. “These horses have no fat, so they can’t store it, so we have to feed them more vitamin E than the normal requirement; they need about 1,500 to 2,000 IU per day,” Cubitt says.

But it is possible to give a horse too much vitamin E. “A person needs to be careful with high doses of vitamin E, because vitamin E and beta carotene [the building block for vitamin A] have the same absorption pathway,” says Williams. “We found that high levels of vitamin E can actually decrease the level of beta carotene in the body. In one study, 10,000 IU of vitamin E was fed daily, and there was some interference with uptake of vitamin A. You are inhibiting one vitamin by overfeeding another.”

Horses on pasture would probably be getting adequate amounts of vitamin A, because beta carotene is also abundant in green grass. “If they are in stalls being fed hay, however, receiving too much vitamin E could become a problem,” Cubitt says.

Your horse’s vitamin E status

Your horse’s turnout schedule and activity level can provide clues to whether he’s taking in enough vitamin E, but a blood test is the best way to determine with some certainty.

“If your veterinarian tests plasma or serum concentrations for alpha-tocopherol, greater than 2 micrograms per milliliter is considered adequate, 1.5 to 2 micrograms would be considered marginal and less than 1.5 would be considered deficient,” Cubitt says. “If we were able to examine horses in the wild and measure their blood levels seasonally, by the end of winter they might be marginal, but that level would soon increase once the spring grass starts growing.”

If your veterinarian suggests that you increase the amount of vitamin E in your horse’s diet, you have several options. Obviously increasing his access to fresh grass will help—assuming this won’t put him at risk of laminitis or obesity. Grass contains somewhere between 30 to 100 IU of vitamin E per kilogram of dry matter.

Click here to learn about the differences between natural and synthetic Vitamin E.

You may also want to see if you can get hay that has been cut earlier—grasses cut for hay while young and growing will have higher levels of vitamin E. Exactly how much of the vitamin hay loses, and how quickly, depends on several factors, including the conditions of harvest and the amount of sunlight it is exposed to when drying (sunlight denatures all vitamins). One study found that fresh alfalfa hay lost as much as 73 percent of its vitamin E after just 12 weeks in storage. In addition, some grains, such as corn, oats or barley, contain some naturally occurring vitamin E but only about 20 to 30 IU per kilogram of dry matter. Grains also lose some of their vitamin E over time in storage; dry, dark storage is best for all feedstuffs.

To avoid uncertainty and ensure that their horses receive what they need, many owners opt for supplements, balancer rations and commercial feeds formulated to provide the nutrients required by average horses or those at specific life stages or activity levels.

“Most commercial feed products are fortified with vitamins and minerals,” says Williams. “They usually provide about 100 to 150 IU of vitamin E per pound. So if a horse is eating two or three pounds of grain daily, this will be adequate if at maintenance or light work.” Vitamin E is included in a wide range of supplements, both as the primary ingredient and as an addition to products for joint health, digestive support and other formulas. However, if the goal is for a level of 5,000 IU per day, make sure you are feeding a sole concentrated source of vitamin E. Otherwise there is a risk of over- supplementing the other nutrients in the product to get to that level of E.

When it comes to keeping a horse healthy, often the best approach is the “natural” way—mimicking as closely as possible the way he would live in the wild—despite stalls, trailers and training schedules. When it comes to an essential nutrient like vitamin E, that means letting him graze as much pasture as possible during the warmer months. But when that’s not feasible, taking steps to make sure your horse gets enough of this essential nutrient will help to keep him healthy.