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A Tale of 3 Selenium Levels: Connection with health and lameness

Selenium and vitamin E are often two of the most common supplemented antioxidants in horses, often attributed to poor soil conditions and likewise perceived deficiencies in the patient.  They are both important antioxidants and vital to cellular health, but all too often, we just supplement without justification or even more, we fail to see rationale for the need for supplementation.  Each horse is different and just because a region is perceived as deficient in selenium or a forage is low in vitamin E, does not always equate to the need for supplementation in every horse.  We need to look deeper, connect the dots and seek deeper, underlying problems which may be addressed adequately.

Selenium, Horse Health and Lameness
Selenium, Horse Health and Lameness

Vitamin E and selenium are both antioxidants found in hay and forage accessible by the horse.  They are both involved in many cellular processes, aid the body in combating oxidative damage present in everyday life and involved heavily in normal immune function.  There are several reasons for deficiencies in the equine patient, but not always associated with low levels in forage or hay.  Unfortunately, a deficient food source is usually blamed for most of the problems, but this is not always the case and may actually NOT be the case in a high percentage of situations.

As a veterinarian, we look at a lot of bloodwork, which often includes evaluating for things like anemia, which is a low red blood cell count.  If we have a patient that is anemic, we really have three possible reasons for this; the cells are being lost (bleeding), not being produced or being destroyed.  We can’t really jump to any conclusion as to the cause, unless there is obvious blood loss, until we do further diagnostic testing.

This same rationale is true when we look at vitamin E or selenium.  In many cases, such as neurological problems including Lyme or EPM, vitamin E is part of the therapy in high doses, although many of these patients are never tested to justify this supplementation.  If we did test a patient, in some cases, we find that they are low in vitamin E, selenium or both.  So again, just like with red blood cells and anemia, we have a few reasons as to why this could be. The first reason would be a deficient intake or deficient food source.  The second would be poor gastrointestinal health and low ability to absorb nutrients from the diet. The final reason would be an increased demand, in relation to the level of intake, by the body.  

We are all familiar with deficient food sources, some regions more prone to this than others.  But, just because a food source is ‘deficient’, this does not necessarily justify the need for supplementation in a patient unless deficiency is proven by bloodwork.  It is theoretically possible to induce toxic like states in patients with over supplementation of both vitamin E and selenium, so one has to be careful.  In reality, antioxidants are best used in combinations, for if we overdose one antioxidant or just focus on one antioxidant, we really could contribute to a oxidative condition.  Antioxidants help the body to neutralize free radicals by donating an electron, and when this electron is donated, the antioxidant actually becomes unstable and a free radical itself.  Thus, other antioxidants are needed to help neutralize and recharge that antioxidant to help prevent further damage.

Digestion is one topic that we have discussed in several articles, ranging from gastric ulcers and heavy use of anti-ulcer medications to leaky gut syndrome. In many of these cases, we actually have underlying inflammation within the bowel, which not only creates issues for the patient, but can decrease the absorptive ability for many nutrients, including vitamin E.  In one study on Equine Motor Neuron Disease, it was discovered that indeed many of these patients were deficient in vitamin E which justifies supplementation, but what was further interesting was the potential cause of this deficiency.  It wasn’t really due to a poor food source, but more so to an underlying eosinophilic enteritis or inflammation within the GI tract.  This inflammatory GI pattern was found in many of these EMND patients and thus believed to be a potential reason as to why they had vitamin E deficiencies, associated with secondary poor absorptive ability. So, this raises the question that we have addressed, in regards to underlying GI disease, inflammation and reduced ability to absorb nutrients.1

The third reason for deficiency in a patient is increased demand by the body in relation to level of intake via the diet.  We have to remember that both vitamin E and selenium are antioxidants, helping to quench free radicals generated during inflammation and stress in the body.  The higher the levels of inflammation and stress, the higher the free radicals generated and the higher the need for antioxidants.  Thus, if a patient is inflammed or stressed, then the need will rise, often exceeding intake.  However, the mistake we make in these cases is that supplementation of vitamin E or selenium is chosen often as the route of therapy, instead of seeking out the cause for the increased demand and rectifying that situation.  It is much like a pool that is leaking water. We can choose just to replace or supplement the water OR we can supplement water AND find the leak.

To demonstrate this, let’s look at three (3) seperate horses, all on the identical diet of alfalfa, whole grains and pasture. In all three horses, full bloodwork was completed along with early morning cortisol, vitamin E and selenium levels.

Levels of vitamin E and selenium are reported as values and often below ‘normal range’ but determined to be ‘adequate” or “marginal” by the laboratory. In most cases of “adequate” levels, supplementation really does not yield clinical benefits.  In cases of “marginal” levels, supplementation is questionable but often advised, still not completely certain if supplementation will yield benefits.

Horse #1:  11 y.o TB gelding, prior eventer retired due to chronic SI injury due to trauma as a yearling. Quiet personality, sound under saddle and currently a low level jumper.  Supplementation consists of Cur-OST® EQ Plus daily.

  • Bloodwork (CBC/Chem) normal
  • Cortisol 4.1 (normal range 1.0-4.6)
  • Selenium 117 ng/ml (normal 160-275) “marginal levels”
  • Vitamin E 3.55 (Adequate levels)
  • Lactate Dehydrogenase 193 iu/L (normal 140-440)

Horse #2: 6 y.o OTTB gelding, current low level jumper, anxiety concerns, thin soles.  Currently on Cur-OST® EQ Total Support.

  • Bloodwork (CBC/Chem) normal
  • Cortisol 6.1 (normal 1.0-4.6)
  • Selenium 183 ng/ml (normal 160-275)  “Adequate”
  • Vitamin E 1.66 (marginal levels)
  • Lactate Dehydrogenase 367 iu/L (normal 140-440)

Horse #3: 7 y.o TB, prior eventer, currently low level jumper, anxiety issues, ulcer history, intermittent tender feet/thin soles.  Currently on Cur-OST® EQ Total Support.  Prior evaluation of feces for leaky gut and bacteria overgrowth are positive, intermittently when stress and anxiety levels are high.

  • Bloodwork (CBC/Chem) normal
  • Cortisol 5.4  (normal 1.0-4.6)
  • Selenium 106 ng/ml  (normal 160-275) “marginal levels”
  • Vitamin E  2.12  ug/ml  (Adequate levels)
  • Lactate Dehydrogenase 315 iu/L  (normal 140-440)

Looking at all three horses, they are on idential diets, same pasture, but different supplements, however, the vitamin E level supplied by the Cur-OST® EQ Plus and EQ Total Support are identical, so supplementation is not a factor.  The first horse is not a stressed animal, very quiet and seems very content with no major health of lameness issues of concern.  The second and third horse are more high stress, high anxiety and both have concerns when it comes to thin soles and intermittent lameness associated with this condition.  In actuality, despite high nutrition and corrective barefoot trimming, their feet tend to do well one month, then quickly go to the negative side, demonstrating tenderness for no apparent reason as all.  The foot growth in both the second and third horse is also slower and of lower quality, as compared to the first horse.  The third horse, interestingly enough, does demonstrate evidence of leaky gut and altered bacterial fecal counts during times of high stress. Again, diets are identical.

Cortisol is one measure of high stress in a patient, as with stress, the adrenal gland secrete cortisol.  As we can see, the first patient has normal cortisol levels first thing in the morning, while the other two horses are elevated.  Seeing this, we now know the second and third horse are experiencing stress. The first horse, non-stressed, has adequate levels of both selenium and vitamin E.  The second and third horse have lower levels. The second horse has high levels of selenium, but vitamin E is low.  The third horse (highest stress patient clinically) has lower levels of both selenium and vitamin E.

The final enzyme measured was LDH or lactate dehydrogenasae.  This enzyme is commonly elevated with excessive muscular activity, due to increased demand by the muscle for energy production and likewise cellular death and release of the enzyme.  Elevated LDH levels are also found associated with several human conditions from heart failure to cancer. In theory, one could connect a higher level of LDH with the stress response.

In all three horses, LDH levels were within the ‘normal’ limits, but in the second and third horse, LDH levels were much higher leaning towards the high end of the normal range.  Is there a connection with the elevated cortisol levels and clinical stress in those patients?

To summarize what we are seeing, we have three horses on identical feed regimens and similar levels of supplementation, however, in two we have clinical stress and intermittent lameness concerns.  We see that with the elevated stress, the cortisol levels are higher and likewise, we have a decrease in selenium, vitamin E or both, as with stress, we have inflammation and free radical drainage.  The higher the free radical levels, the higher the need for antioxidants, thus potentially a drain on the system or influx.  The take home point here is that IF we just tested the horses with thin soles for vitamin E or selenium, then supplemented based on the test results, we may be missing the problem or underlying cause, which is the stress response.

At this point, we have not changed supplementation for horse number one, but have modified the supplementation for horse number two and three.  The last two horses are being supplemented with a new Cur-OST® research formula, combining the effects of the EQ Adapt with several other adaptogens to help further quench the stress response and provide support.  In addition, the third horse is being also placed on the EQ Stomach formula to help soothe the GI tract and quiet any subclinical ulcers which may be present. Bloodwork will be repeated after one month of supplementation to compare with initial values, but already at day 3 of supplementation, clinically both horses are quieter and more relaxed in the morning.  The other notable positive change is that sole tenderness has improved about 80% in 72 hours.

In the end, we have to remember that nutrients are vital to health but a deficiency should not only pose the question of adequacy in diet, but also raise concerns of an ongoing ‘drain’ on the body.  This second point is one that is not often adequately addressed and likewise might explain the ongoing problems in horses despite supplementation.

Thank you.

Tom Schell, D.V.M., CVCH

Nouvelle Research, Inc.





1. Diez de Castro, E et al. Eosinophilic Enteritis in Horse with Motor Neuron Disease. J Vet Intern Med, 2016, May; 30(3):873-879


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