VITAMIN E KEY TO EQUINE HEALTH 2018
At the Center for Equine Health (CEH), we continually strive to bring you the latest in
equine health through this award-winning publication.
This particular issue of Horse Report is near and dear to my own research program.
My research team studies the consequences of vitamin E deficiency in the horse. In this
Horse Report issue, we focus on the importance of vitamin E as part of a well-rounded
nutritional regimen. For horses in areas with lush green pastures, vitamin E is abundant,
as the grass consumed in a normal grazing routine provides a sufficient amount. But most
of us in California know that lush green pastures are an extreme luxury due to recent
drought conditions. As a result, many of our horses require vitamin E supplementation.
This powerful antioxidant protects against cell damage from free radicals.
You may be familiar with the importance of vitamin E in human diets. Its advantages
include an increased immune system response, balanced cholesterol levels, lower
inflammation, natural repair to damaged skin, and balanced hormones. Most importantly, however, is its ability to
prevent debilitating neuromuscular disease. This also holds true for horses. In this issue, we will discuss these diseases
and give you information on how to properly supplement your horse’s diet.
With your help, CEH continues to advance the well-being of horses and educate horse owners on the latest discoveries
in horse health. At UC Davis, we are at the forefront of research into the importance of vitamin E in the equine diet.
What an exciting time to be part of our journey!
Thank you for your continued support,
Carrie J. Finno, DVM, Ph.D.
CEH Director
Due to the importance of vitamin E
in every horse’s diet, the Center for
Equine Health has invested in irrigating
its pastures for the teaching herd.
Since the best source of vitamin E is
fresh green grass, these lush pastures
at UC Davis provide an ideal
environment for the teaching herd
to graze.
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CENTER FOR EQUINE HEALTH – HORSE REPORT • FALL 2018
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Recovery from Vitamin E Deficiency
Meet the Scientists Behind the Discoveries
Tarnisha, a 10-year-old
Thoroughbred, came to live
at the CEH in 2012 after her
owners donated her following an
injury that forced her retirement
from racing. Three years later,
she began showing clinical signs
of muscle wasting and weakness.
The Finno Laboratory at the CEH
diagnosed her with vitamin E
deficient myopathy, confirmed via
muscle biopsy. She was started on
a treatment plan consisting of oral
vitamin E supplementation and
showed improved clinical signs
within two weeks. She continued
to make steady improvements and
has never looked back. To maintain her health, she will need to remain on oral supplementation for the rest of her life or live
on green pasture. “Tarnisha is a perfect example of how quickly some horses can improve from vitamin E deficient myopathy
simply with the proper supplementation,” said CEH Director Carrie Finno. “This is the one disease that horses can completely
recover from with appropriate treatment.”
Hadi Habib recently graduated
from UC Davis with a bachelor’s
degree in Chemistry and a master’s
degree in Forensic Science with an
analytical chemistry focus. Hadi’s
research quantified vitamin E and
vitamin E metabolite levels in horse
blood, particularly in serum and
plasma. Vitamin E actually consists of
eight compounds that can be measured
individually. To investigate how fast a
horse “uses” vitamin E and each of these
eight compounds, vitamin E metabolites
are measured. Under the mentorship
of Drs. Birgit Puschner and Ingrid
Gennity, Hadi developed a method to
measure levels of all of the components of vitamin E and its
metabolites in equine plasma and serum. Quantification was
achieved using analytical instrumentation (UHPLC-MS/MS).
The validated method determined concentrations of
these analytes in plasma and serum of horses. Assessment
of vitamin E and metabolites is a critical component of
diagnostic investigation in horses with neuromuscular
diseases. Alpha-tocopherol (isoform of
vitamin E) levels were found to range from
3-6 µg/mL, while the metabolites were found
at much lower levels, ranging from .0002 –
.0010 µg/mL in healthy horses. This work
has been pivotal in investigating the rate at
which certain horses “use,” or metabolize,
vitamin E. The team is discovering that
some horses may require higher doses of
vitamin E than others, based on a more rapid
metabolism of the vitamin.
Hadi performed his training through the
Bioanalytical Research Core, a unique
interdisciplinary analytical core that provides
method development and validation for
therapeutics and toxicants in support of
the School of Veterinary Medicine’s drug discovery efforts.
Core members have advanced training and experience
both in the pharmaceutical industry (preclinical drug
development) and academia as well as extensive experience
with pharmacokinetic modeling of drug and metabolite
concentration data in a variety of biological matrices (blood,
urine, milk, synovial fluid, tissue).
Before After
Hadi Habib
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SCHOOL OF VETERINARY MEDICINE • UNIVERSITY OF CALIFORNIA, DAVIS
Vitamin E: Key to Equine Health
uncoordinated. They may stand with forelimbs too far
apart (or too close), have difficulty navigating curbs or
hills, or lack coordination while walking and making tight
turns. Manifestations of the disease can vary among horses
with some showing mild performance issues, while others
are severely debilitated. Although there is no cure yet for
eNAD, one of most common equine neurological diseases,
researchers are closing in on how to prevent the onset of
symptoms—and early intervention is key.
Dr. Carrie Finno, director of the CEH, said studies show
that vitamin E is necessary to prevent degeneration of the
neurons and axons throughout the brain and spinal cord
during early life in many species. Axons are the part of nerve
cells that transmit impulses, so when those cells are damaged,
communication breaks down between the brain and the rest
of the body, leading to a lack of coordination.
“We still don’t understand the cause of the degeneration, but
we do know there is an interaction between genetics and
nutrition for this disease to manifest,” Finno said. “You need
the perfect storm of genetic susceptibility and a deficiency of
vitamin E during the first few years of life.”
Researchers in the Finno Laboratory are working hard to
develop a genetic test for eNAD, but until one is available, she
advises horse owners to supplement their horses, especially
pregnant mares and newborn foals. The supplement may
Proper nutrition—particularly appropriate levels of
vitamin E—is critical to equine health. This biological
antioxidant helps maintain normal neurological function
by limiting the damage caused by oxidative stress and free
radicals. The best source of this nutrient is fresh green grass.
As soon as the grass is dried for hay, the potency of vitamin E
in the forage declines dramatically.
Many research studies, including some conducted at the
Center for Equine Health (CEH), have shown that horses
without access to grazing on green grass are often deficient in
this essential mineral, which leaves them vulnerable to three
different types of neuromuscular diseases associated with
vitamin E deficiency: equine neuroaxonal dystrophy/equine
degenerative myeloencephalopathy (eNAD/EDM), equine
motor neuron disease (EMND) and vitamin E deficient
myopathy (VEM). These diseases are typically diagnosed
based on the clinical signs, exclusion of other disorders and a
low blood vitamin E concentration.
While not all animals deficient in vitamin E exhibit clinical
signs, individual genetic factors, the age of the horse during
deficiency (such as early growth phases), and the duration of
deficiency all play a part in determining whether insufficient
levels of vitamin E in a horse’s diet will impact their health.
Equine neuroaxonal dystrophy occurs in young animals
and has a genetic predilection. Affected horses appear
Cover Story
Cut grass is not a good source of vitamin E since
nutrient levels start to diminish at harvest.
Mares and foals are especially
susceptible to vitamin E deficiency.
Dr. Carrie Finno examines a case of equine motor neuron disease
displaying the abnormal stance with all four feet placed close
together underneath the horse.
not entirely eliminate the disease, but it does appear to
result in less severe neurological signs if the foal receives
supplementation during the early stages of life.
Equine motor neuron disease occurs in older horses that
have been vitamin E deficient for more than 18 months. It
affects lower motor neurons, nerves that supply the direct
neurological input into all muscles. Without these, the
associated muscles atrophy, resulting in the clinical signs
of weakness and weight loss characteristic of this disease.
Affected horses may carry their heads lower and lie down
for longer periods of time. With treatment, approximately
40 percent of horses affected by EMND improve; 40 percent
stabilize but remain disfigured; and 20 percent progress in
severity of disease.
Vitamin E deficient myopathy is typically found in horses
with a shorter duration of vitamin E deficiency and exhibit
muscle weakness, low muscle alpha-tocopherol concentration
and mitochondrial alterations (i.e. changes to the “power
house” energy storage unit of the cell) in skeletal muscle
but no evidence of neurogenic atrophy. These animals are
generally able to recover within three months with proper
supplementation.
These three diseases are the only conditions definitively
associated with vitamin E deficiency. Despite this, many
horses with neurologic disease caused by other diseases (i.e.
equine protozoal myeloencephalitis, or EPM, and cervical
compressive vertebral myelopathy, or “Wobblers”) are placed
on vitamin E supplementation.
“At this time, we know nothing about vitamin E metabolism
in horses, the appropriate dosage or its actual efficacy in
preventing or treating neurological conditions other than
eNAD, EMND and VEM,” said Finno, who was appointed as
the inaugural holder of the Dr. Gregory L. Ferraro Endowed
Directorship this spring. “Supplementation with vitamin E
may alter drug metabolism and disposition, since, in humans,
the same cytochrome isoforms that metabolize vitamin E
metabolize approximately 50 percent of therapeutic drugs.”
Therefore, while vitamin E supplementation may not
necessarily be harmful for these other neurologic diseases,
it is unlikely to be beneficial. Baseline blood vitamin E
concentrations should always be assessed before initiating
any vitamin E supplementation.
Finno notes that recent droughts in California may
also contribute to the decline in forage with sufficient
vitamin E levels. Her laboratory is currently
conducting research into how both healthy horses
and horses with neuromuscular disease metabolize
vitamin E. There may be an underlying genetic variation
in certain horses that results in them having a higher
requirement of vitamin E. When these horses are then placed
in a vitamin E deficient environment, such as a dry lot in
California, neuromuscular disease may develop. If the Finno
Laboratory can identify which horses require more vitamin
E than others, supplementation could be individualized to
prevent disease in those individuals.
“Continued research into this vital nutrient is critical to
promoting equine health,” Finno said. “Especially for those
horses that live in areas where access to green pasture is
limited, like many areas in this state.”
For more information on vitamin E deficiency and suggested
supplementation, please see the accompanying article in this
issue of the Horse Report.
CENTER FOR EQUINE HEALTH – HORSE REPORT • FALL 2018
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SCHOOL OF VETERINARY MEDICINE • UNIVERSITY OF CALIFORNIA, DAVIS
Importance of Vitamin E
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
A case of eNAD/EDM displaying an
abnormal stance due to damage of the
proprioceptive tracts.
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SCHOOL OF VETERINARY MEDICINE • UNIVERSITY OF CALIFORNIA, DAVIS
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
Vitamin E, an essential nutrient for horses, can
be acquired by grazing in lush green pastures.
CENTER FOR EQUINE HEALTH – HORSE REPORT • FALL 2018
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Horses in dry pastures, especially mares
and foals, need vitamin E supplementation.
CENTER FOR EQUINE HEALTH – HORSE REPORT • FALL 2018
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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 year-
round 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” water-
dispersible). 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.
The Horse Report is published by the University of California, Davis, School of Veterinary
Medicine: Michael D. Lairmore, dean; Carrie Finno, CEH director; Tom Hinds, director strategic
planning and communications; Rob Warren, editor; Katie Blakewell, Don Preisler, Carolyn
Sawai, Trina Wood, contributors. The Center for Equine Health is supported with funds
provided by the State of California Pari-Mutuel Fund and contributions from private donors.
The University of California does not discriminate in any of its policies, procedures or practices.
The university is an affirmative action/equal opportunity employer.
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Center for Equine Health
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University of California
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Davis, CA 95616-8589
We are grateful to equine enthusiasts like you who share our commitment to the
well-being of horses. Thanks to generous support, we continue to make great strides
in advancing equine health to help horses like Tarnisha, highlighted in this issue of
Horse Report. Please consider joining us in our mission by becoming a partner today.
The welfare of horses depends on the improvement and advancement of equine
medicine. To make a gift to the Center for Equine Health, call our Advancement team
at 530-752-7024 or visit give.ucdavis.edu/Go/CEH.
www.vetmed.ucdavis.edu