Why Deficiency Is More Common This Time of Year—and Why Thoroughbreds Are at Higher Risk

The Effects of Vitamin E on Fascia, Muscle, and Nerves

Why Deficiency Is More Common This Time of Year—and Why Thoroughbreds Are at Higher Risk

Vitamin E is a critical antioxidant for the horse’s most sensitive systems. It supports muscle integrity, nervous system function, immune resilience, and recovery from work. When levels drop, the effects are often felt first in movement quality, coordination, and tissue comfort.

Because horses cannot synthesize vitamin E on their own, they rely almost entirely on fresh, green forage for intake. Seasonal changes—and certain management patterns—make deficiency far more common than many owners realize, particularly in Thoroughbreds.

Before looking at why deficiency increases this time of year, it helps to understand how low vitamin E affects the body.

Why Vitamin E Matters

Vitamin E plays a foundational role in:

• Muscle health and recovery
• Nervous system stability
• Immune support
• Performance and stamina
• Protection against muscle soreness, cramping, and tying up

When vitamin E is insufficient, oxidative stress rises—placing strain on muscle fibers, fascia, and nerves.

Effects of Low Vitamin E on the Body

Effects on Muscle

Vitamin E deficiency can contribute to:

• Increased muscle cell damage from oxidative stress
• Slower repair of normal micro-tears
• Reduced clearance of metabolic waste
• Greater post-exercise soreness
• Stiffness, cramping, or tying up (especially common in Thoroughbreds)
• Difficulty developing or maintaining topline
• Delayed recovery after routine work

Muscles fatigue faster, repair more slowly, and remain sore longer when vitamin E is low.

Effects on Fascia

Fascial tissue depends heavily on antioxidant support to maintain glide, hydration, and elasticity. Low vitamin E can lead to:

• Reduced fascial glide
• Thickened or “sticky” fascial layers
• Increased whole-body stiffness
• Compensatory tension patterns
• Slower or incomplete response to bodywork
• Decreased force transmission through myofascial lines

As fascial elasticity declines, many horses develop the tight, rigid feel owners often notice during winter months.

Effects on the Nervous System

Vitamin E is essential for nerve health—particularly long peripheral nerves serving the limbs, back, and hindquarters.

Deficiency may cause:

• Increased nerve irritability
• Muscle fasciculations (twitching)
• Poor proprioception
• Stumbling or uncoordinated movement
• Hypersensitivity to pressure or touch
• Vague neurologic signs that resemble weakness
• Difficulty maintaining coordination under saddle

Even mild deficiency can make a horse feel shaky, twitchy, weak, or unbalanced.

Horses Without Pasture Access: A Year-Round Risk

Some horses receive little to no fresh pasture at any time of year, placing them at ongoing risk for deficiency. This includes:

• Metabolic horses kept on dry lots
• Horses with restricted turnout
• Horses in desert or arid regions
• Horses boarded at facilities with limited grazing
• Horses kept in sand pens or small paddocks

These horses often require year-round vitamin E support, not just seasonal supplementation.

Why Vitamin E Deficiency Is More Common This Time of Year

Pasture Quality Drops Dramatically

From late fall through early spring:

• Grass becomes dormant
• Green content declines
• Vitamin E content drops sharply
• Grazing time often decreases
• Many horses move to dry lots or sacrifice paddocks

Fresh grass is the primary natural source of vitamin E. When it disappears, intake falls quickly.

Hay Contains Very Little Vitamin E

Even high-quality hay loses up to 80% of its vitamin E within:

• 6–8 weeks after cutting
• And continues to degrade during storage

By winter or early spring, most hay contains virtually no vitamin E. This includes alfalfa, which also loses vitamin E during curing.

Seasonal Changes in Workload

Winter routines often change, increasing oxidative stress and vitamin E demand:

• Modified training programs
• Indoor riding and footing
• Trailering
• Cold-weather stiffness
• Inconsistent exercise schedules

This creates a higher need paired with lower intake.

Confinement and Reduced Movement

Increased time spent in:

• Stalls
• Dry lots
• Small paddocks

reduces circulation and raises oxidative load, further increasing antioxidant requirements.

Feed Alone Is Often Insufficient

Many horses rely on:

• Ration balancers
• Basic grain mixes
• Senior feeds

Even fortified feeds may not meet vitamin E needs unless fed at full recommended amounts. Most horses require 1,000–2,000 IU per day, while performance horses may need 2,000–5,000 IU per day.

Why Thoroughbreds Are More Prone to Vitamin E Deficiency

Professionals frequently observe deficiency signs in Thoroughbreds, and several factors explain why.

Higher Metabolic Demand

Thoroughbreds tend to have:

• Faster oxidative turnover
• Higher metabolic rates
• Stronger stress responses

This means antioxidants—including vitamin E—are used more rapidly.

Greater Susceptibility to Muscle Disorders

Thoroughbreds are more prone to:

• Tying up (RER)
• Muscle soreness
• Fasciculations
• Exercise intolerance

Low vitamin E increases both the severity and frequency of these issues.

Muscle Fiber Composition and Nervous System Traits

Key contributors include:

• Predisposition to RER
  Many Thoroughbreds have altered calcium handling in muscle cells, leading to prolonged contraction and cramping.
• Fast-twitch muscle dominance
  Built for speed and power, these fibers generate more heat and oxidative stress, increasing vitamin E requirements.
• High baseline sympathetic tone
  A naturally reactive nervous system keeps muscles closer to contraction, raising the risk of spasms and soreness.

Common Management Patterns

Many Thoroughbreds experience:

• Limited turnout
• Increased stall time
• Higher-starch diets
• Environmental and training stress
• Inconsistent exercise patterns

All of these increase oxidative load and deplete vitamin E reserves.

Transition from the Track

Horses coming off the track often arrive with:

• Prolonged stall confinement
• Hay-based diets
• High muscular stress
• Existing nutritional gaps

Many begin their second careers already deficient.

Lower Antioxidant Reserve

Thoroughbreds typically have:

• Lower natural fat stores
• Fewer reserves of fat-soluble nutrients
• Faster depletion of vitamin E

As a result, deficiency signs may appear sooner and more subtly.

Common Signs of Low Vitamin E

Signs frequently seen in winter and in Thoroughbreds include:

• Muscle twitching
• Loss of topline despite adequate feed
• Poor stamina
• Slow recovery after work
• Weakness or stumbling
• Vague hind-end issues
• Difficulty holding bodywork or training changes
• Nerve hypersensitivity
• Reduced immune resilience

Early signs are often subtle, especially in Thoroughbreds.

Supplement Form Matters

Not all vitamin E supplements are absorbed equally.

In horses:

• Natural d-alpha-tocopherol is better absorbed than synthetic dl-alpha-tocopherol
• Water-dispersible (micellized) forms are ideal for low-fat diets or deficiency states
• Powdered synthetic forms may fail to raise blood levels in some horses

For horses showing symptoms, a high-quality natural, water-dispersible form is often most effective.

Selenium: An Important Caution

Vitamin E is frequently paired with selenium, but caution is essential:

• Many feeds and balancers already contain selenium
• Excess selenium can be toxic
• Avoid stacking multiple E/Se products without calculating totals

Always review selenium intake with a veterinarian before adding selenium-containing supplements.

When to Involve Your Veterinarian

Consider veterinary testing if you observe:

• Persistent muscle twitching
• Unexplained weakness or coordination issues
• Progressive topline loss
• Vague neurologic signs
• Chronic soreness or delayed recovery
• Sudden behavior changes that feel neurologic

A simple serum vitamin E test can confirm deficiency and guide appropriate dosing.

Other Horses at Increased Risk

Beyond Thoroughbreds, deficiency may appear sooner in:

• Older horses
• Horses in intense or sustained work
• Horses with chronic pain or compensation patterns
• Metabolic horses kept off pasture
• Horses recovering from illness or injury

These horses may benefit from proactive support.

Big-Picture Takeaway

Vitamin E deficiency becomes more common this time of year because:

• Fresh pasture disappears
• Hay contains little to no vitamin E
• Workload changes and confinement increase oxidative demand

Thoroughbreds are especially vulnerable due to:

• Higher metabolic demand
• Heightened stress reactivity
• Muscle sensitivity and RER tendencies
• Common feeding and turnout patterns
• Lower antioxidant reserve capacity

Supporting vitamin E intake appropriately is one of the most effective ways to protect muscle, fascia, and nerve health—particularly through the winter months and in sensitive horses.