Vitamin E and the Performance Horse
Dr Peter Huntington and Dr Kathleen Crandell and Ms. Elizabeth Owens

Have you ever watched another horse which has

extravagant movements, stretching out over the

full workout or competition? The answer to

improving your horse’s comfort and performance

may be as simple as adding a vitamin to his/her

diet. Vitamin E has been used in the racing

industry for many years and its importance to

performance horse owners is just beginning to be

recognised.

Vitamin E is a non-toxic, fat soluble vitamin

which has an important role in many

physiological functions such as, reproduction,

immune response, nerve and muscle function. It

also has overlapping yet independent roles with

an essential trace mineral, selenium. Together

they act to maintain normal muscle function, aid

in the prevention of muscular disease and by

performing as antioxidants protect the body

tissue, particularly cell membranes, enzymes and

other intracellular substances, from oxidation

induced damage. If vitamin E levels in the

muscle tissue are inadequate, then the risk of

exercise-induced muscle damage is increased.

One important function of vitamin E is to

interrupt the production of free radicals at the

initial stage of peroxidative damage. Free

radicals attack membranes and cells causing

tissue damage. The more active the cell (cells of

skeletal and involuntary muscles) the greater the

use of fats for energy supply and the greater the

risk of tissue damage if vitamin E is limiting.

A deficiency of vitamin E may cause a variety of

different symptoms and pathological changes,

which may include poor immunity to diseases (eg

recurrent cold and cough), muscle stiffness and

soreness or damage. The result would be

reduced physical performance, especially when

endurance is important. It is known that the

horse is not very efficient in storing vitamin E,

although body stores may contain sufficient

vitamin E to cover for 4 months of inadequate

intake in the non-exercising horse. The onset of

a deficiency may be accelerated when the diet is

insufficient in selenium. Unlike other animals, a

diet that is high in unsaturated fatty acids from

vegetable oils does not appear to increase the

requirement for vitamin E in the horse, although

pre mixed feeds that are high in fat require extra

vitamin E to prevent oxidation of the fat in the

feed. This is important in feeds that are stored

for a period of time before use as vitamin E will

be used up to prevent fat oxidation during

storage.

For the horse which is kept in a paddock, fed

entirely on green grass, it is unlikely that it will

have a vitamin E deficiency, however, not every

horse is that lucky. While roughages such as

lucerne, green pasture and good quality green

hays are excellent sources, the content is

variable and is reduced by maturity, harvesting

and storage. In the process of hay making,

between 30 to 80% of vitamin E activity is lost

between cutting to baling the hay and even more

is lost during storage. Vegetable oils are

relatively high in Vitamin E but are generally not

fed in sufficient quantities to make a big impact

on supply of this vitamin in the diet. Feeds which

contain lower levels of vitamin E are grains,

chaff and poor quality, weather damaged, or

propionic acid treated hays. The crushing of oats

and grinding of cereals results in rapid

oxidisation of fats and the vitamin E content is

quickly lost unless the feed is pelleted. The

presence of heat and sufficient moisture for

fermentation and mould growth to occur all

decrease the vitamin E content in feeds.

When considering prepared feeds it is important

to note that some contain more than adequate

amounts of vitamin E to meet requirements,

some contain very high levels but others feeds

supply below the required level, so always check

the content. You need to consider how much is

being fed per day as well as the amount of

Vitamin E per kg. The vitamin E level in general

• A Publication of Kentucky Equine Research Australasia Pty Ltd ©• 1800 772 198 • equivit@ker.com • www.ker.com •

•Page 2 of 2 •

mineral and vitamin supplements is often low,

although some, eg. EQUIVIT Gold Pellet, contains

750 IU of vitamin E and specific Vitamin E

supplements are available to “top up” the diet,

eg EQUIVIT Preserve, EQUIVIT E Concentrate and

ELEVATE.

When the workload of the horse increases, the

energy demand increases. To maintain body

condition and energy for work, usually more

grain and less roughage is fed. This means the

horse may be receiving even lower amounts of

vitamin E, because of the lower intakes of the

major source of vitamin E ie: green roughages.

Therefore there is a need to consider vitamin E

supplementation, especially if the horse is

supplied with feeds that are lower in vitamin E.

The quantity of vitamin E or selenium required

relies on the amount of the other that is

available and optimum amounts are needed in

order to prevent clinically apparent disease.

This reinforces the need to consider vitamin E

and selenium together in respect to

requirements and the prevention of deficiencies.

Daily supplementation is recommended in diets

deficient in vitamin E in order to correct the

diet. A periodic vitamin E injection is not

sufficient nor is it advisable as death can occur

from an allergic reaction.

So how much vitamin E is needed? Recent

research indicates that the vitamin E

requirement of horses is much higher than was

thought 10 years ago. 

For hard-working and athletic horses that may be

prone to “tying-up” there is a definite benefit

from vitamin E and selenium supplementation.

These antioxidants can reduce the severity of

exercise induced free radical damage to muscle

cells. In a small percentage of horses that tieup,

supplementation of vitamin E and selenium

alone will alleviate the problem.

Research at the University of Kentucky has

indicated that the requirement may been even

higher than the levels in Table 1 in horses

exercised daily for a prolonged period of time. In

the study horses were trained for 3 months and

vitamin E supplementation of 80 IU/kg diet (800

IU/day) did not maintain blood and muscle

vitamin E levels whereas 300 IU/kg diet (3000

IU/day) did maintain levels. A basal diet

containing less than 40 IU/kg diet (400 IU/day)

also failed to maintain blood or tissue levels of

the vitamin. However vitamin E supplementation

did not change specific indicators of muscle

integrity or damage in an exercise test at the

end of the training period. So the jury is still out,

but it would not be surprising if

recommendations for vitamin E intake were

increased in the near future, particularly for

prolonged duration exercise.

Vitamin E is important for your horse’s health

but it is also an expensive supplement.

Therefore, it is important not to overuse the

vitamin. However, if vitamin E can lead to

improved immune and muscle function, better

performance and a happier horse, the benefits

will outweigh the costs.