Vitamin E for Horses: What Owners Need to Know

 Understanding daily requirements, deficiencies, symptoms & how to support your horse’s health

Vitamin E plays an essential role in your horse’s overall health, supporting muscles, immunity, neurological function, recovery and antioxidant defence. Yet many horses, especially those on restricted grazing or preserved forage diets, may not be consuming enough.

This Equell guide explains what vitamin E does, how much horses need, which horses are most at risk of low intake and how to spot the early signs of deficiency. We’ve also added additional commonly asked questions, including how grazing, hay/haylage, workload and age influence Vitamin E requirements.

Quick Quiz :

True or False – My horse is fed ad lib hay so they don’t need any additional Vitamin E

False – vitamin E levels in hay and haylage are significantly lower than those in fresh grass. Hay is considered low to negligible in Vitamin E from a nutritional standpoint, containing on average 5-30iu per kg, with older hay that has been stored for 6months or more often containing under 10iu/kg. Haylage fairs slightly better being 30-100iu/kg. By comparison, grass contains between 50-400iu per kg (depending on plant maturity/overgrazing etc which reduce values significantly), over 10x the amount found in hay! So horses eating hay only diets will nearly ALWAYS need vitamin e supplementation regardless of the work level they are in as diet alone will not meet nutritional needs. 

Which form of Vitamin E is natural?

• d-alpha tocopherol 
• d-alpha tocopheryl acetate
• dl-alpha tocopherol

Answer – the first two are the natural forms of vitamin E. DL denotes the synthetic version which is much less bioavailable than natural. Studies have shown that the natural form of vitamin E is up to twice as effective as synthetic, being more bioavailable, better absorbed and better retained in tissues, so check carefully when comparing supplements and choose natural vitamin E where possible. Equell use only natural vitamin E in their formulations.

Do you always need to feed selenium with vitamin E?

• Yes
• No
• Only in competition horses

Answer – No. Selenium and Vitamin E are both powerful antioxidants that support against oxidative stress within the horse’s body and maintain healthy cells and tissues, but feeding one without the other will not prevent the other from working.
Selenium is essential for reproduction and normal muscle function - particularly useful for horses with conditions like PSSM and those prone to tying up. Most concentrate feeds contain sufficient levels for normal horses, but for hard working horses, those with muscular conditions, breeding stock or horses needing to build more topline, Equell Muscle Up provides excellent levels of both natural vitamin E, grapeseed extract (3000iu combined) and selenium to support recovery from training and normal muscle function. Remember that over supplementing selenium can be toxic, so consult your vet and or reach out to us if you are unsure. Muscle Up is designed to be fed safely with the levels of selenium typically found in normal concentrate feeds but do not feed with another supplement containing high levels of selenium.

What is Vitamin E and why is it important for horses?
Vitamin E is an essential, fat-soluble antioxidant that aids against oxidative stress. Horses can’t make it themselves, so it must come from the diet. Fresh, green grass is the richest natural source, but levels drop markedly once grass is cut, dried or stored (hay/haylage), and can also fall during winter turnout or stabling/competition routines with limited grazing. That’s why many horses benefit from targeted vitamin E supplementation. As a powerful antioxidant, vitamin E helps neutralise oxidative stress that can compromise muscle, nerve and immune function - supporting comfort, recovery and overall wellbeing.

In horses, vitamin E contributes to:

·         Healthy muscle function and post-exercise recovery

·         Normal immune system activity

·         Nervous system and neuromuscular health

·         Maintaining cellular integrity & function - especially in hard-working horses

·         Nutritional balance for high-forage diets with limited fresh grazing

How much Vitamin E does a horse need?

General guidelines (National Research Council, UK nutritionists) suggest that the vitamin E requirements for an average 500kg horse are as follows:

• Maintenance / light work: 500 -1000 IU per day
• Moderate work: 1200 - 2,000 IU per day
• Heavy work / competition horses: 2,000 - 5,000 IU per day
• Broodmares or growing youngstock: 1,500–2,000 IU per day

Horses with specific neuromuscular challenges may require vet-directed levels far above this. According to one research nutritionist Dr Juliet Getty, horses prone to laminitis or recovering from illness/surgery may require up to 5,000 iu/day whilst those prone to tying up or with severe allergies may need up to 10,000 iu per day! It is important to remember that these are general recommendations and individual needs may vary depending on diet, age, workload, health and condition. Always consult your vet before feeding levels of vitamin E above 5000iu per day. 

Which horses are most at risk of low Vitamin E?

Performance horses need much higher levels of vitamin E than those at rest or in light work. Horses short on vitamin E often show generalised muscle soreness, stiffness or reluctance to move freely, early fatigue and slower post-exercise recovery - all hallmarks of oxidative stress and inadequate antioxidant support. Because vitamin E is a primary fat-soluble antioxidant in muscle and nerve tissue, suboptimal intake can reduce exercise tolerance and training quality. Research conducted by McMeniman & Hintz (1992) reported that horses with lower plasma vitamin E demonstrated reduced exercise tolerance, underscoring the nutrient’s importance in the athletic horse’s feed ration. Ensuring adequate daily vitamin E - especially when fresh grazing is limited - can help maintain comfort, willingness, and consistent performance.

The following horses are more also more prone to vitamin E deficiency:

1. Horses on restricted turnout

Winter, wet fields, livery yard restrictions or weight-management plans all reduce access to fresh grass.

2. Horses on hay-only or soaked-hay diets

Preserved forage contains dramatically less vitamin E, especially hay that has been stored for several months. Soaking hay leaches essential nutrients from the hay and so any levels present before soaking will be further reduced.

3. Good-doers and metabolic horses (EMS, laminitis-prone)

These horses often graze less and diets low in fresh grass can mean lower antioxidant intake.

4. Broodmares and young horses

Growth and reproduction increase antioxidant requirements.

5. Older horses

Ageing influences absorption and metabolism, often increasing requirements.

What are the signs of low Vitamin E in horses?

Symptoms vary and some are subtle at first. Potential indicators include:

• Lack of topline development
• Poor muscle definition despite correct training
• Muscle tightness or longer post-exercise recovery
• Low energy or reduced stamina
• Weak immune response
• Mild coordination changes or muscle fasciculations (twitching)
• Weight loss in older horses
• Sore or sensitive muscles

Always consult your vet if you suspect a deficiency or notice neurological signs.

Is Vitamin E deficiency common in the UK?

Yes especially in:

• Horses stabled through winter
• Horses on calorie-restricted diets
• Natives and good-doers with limited grazing
• Horses fed hay or haylage, which contains significantly less Vitamin E than fresh grass
• Horses that require forage soaking

UK forage testing consistently shows lower-than-expected natural vitamin E levels, particularly from late winter into early spring when stored forage is older.

Can horses get too much Vitamin E?

Excessive vitamin E can interfere with other fat-soluble vitamins, but toxicity is rare and usually linked to extremely high supplemental doses. Always follow recommended feeding guidelines and consult your vet for high-dose use. All Equell formulations are designed to be fed safely alongside normal concentrate feeds, including those that already provide vitamin E.

Does haylage contain more Vitamin E than hay?

Not reliably.
While haylage retains slightly more natural vitamin E than dry hay, levels still fall drastically compared to fresh grass. Both should be considered low-Vitamin-E forages after storage.

Should I test Vitamin E levels?

Blood testing through your vet is the most accurate way to assess status, especially if your horse is:

• On restricted grazing
• Not building topline despite regular, correct training
• Consistently recovering slowly from exercise
• Showing neuromuscular or immune concerns
• Older or metabolic

Testing provides a clear picture before adjusting diet or supplementation.

How do I know how much Vitamin E is in my horse’s feed?

Vitamin E is an additive (whether natural or synthetic, it is still classed as an additive) and inclusion amounts should be listed on the label of your horse’s feed. It is normally stated in iu/kg which shows the total amount of vitamin E included per kg. To work out what your horse is getting, simply weigh out the amount that your horse is eating each day and then calculate. For example:

Feed A contains 2000iu/kg per the label

Your horse gets 600g per day.

600g is 60% of 1kg. 2000/100 x 60 = 1200iu per day of vitamin E for a 600g serve.

Working out the amounts in your base feed, considering whether your horse has access to grass or is on a hay only diet and then factoring in their work level and any muscular or health conditions that require additional vitamin E will help you to understand if your horse requires additional supplementation and if so, how much.

How do you increase Vitamin E intake naturally?

• Provide as much safe grazing as possible (do not allow free access to grass for laminitic horses/ponies or those that are metabolic – provide safe grazing for those horses that CAN have grass and supplement higher levels of vitamin E for those who cannot)
• Use fresh hay rather than older batches when available
• Feed a high-quality balancer with vitamin E included
• Support muscle and antioxidant needs with specialised supplements such as Muscle Up, which contains amino acids and antioxidants (including Vitamin E, grapeseed extract – 3000iu per day - and selenium) to complement a forage-based diet

Other Equell supplements that include natural Vitamin E include:

-          Ultraflex (3000iu per day)

-          Ulceraid (1500iu per day)

-          UltraMet (1500iu per day)

The above iu’s are based on the daily serve for a 4-600kg horse of combined vitamin e and grapeseed extract - a potent combination shown in animal studies to be very effective together! If you require help working out the levels for a smaller or larger horse, please reach out to our team via info@Equell.co.uk and they will be delighted to help!

 

Additional common owner questions:

Do older horses need more Vitamin E?

Yes - aging affects absorption and muscle recovery, increasing vitamin E requirements.

Does soaking hay remove Vitamin E?

Yes, soaking reduces water-soluble nutrients, and stored hay is already low in vitamin E. Soaked forage diets almost always require supplementation.

Can lack of Vitamin E affect topline?

Low vitamin E can contribute to poor muscle definition and slower recovery, making it harder for horses to build and maintain topline.

Is Vitamin E helpful for horses in hard work?

Performance horses experience more oxidative stress, so vitamin E helps maintain muscle function, optimal performance and post-exercise recovery.

Final Thoughts

Vitamin E is essential for muscle health, immunity and overall wellbeing, yet many UK horses simply don’t consume enough through forage alone, especially during winter or restricted grazing. Understanding your horse’s needs and knowing the signs of deficiency can help you protect long-term health, performance and comfort.

For horses needing additional muscle or antioxidant support, choosing a supplement with high levels of natural vitamin E and functional amino acids like Equell Muscle Up can help bridge the dietary gap to support overall wellbeing without unnecessary calories or unwanted fizz.

The Equell Team, 13.12.25