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Selenium is an essential nutrient often times lacking from grazing animals normal feed.  It is very important to take a look at the way we feed and supplement this to our animals. Our mission at Horse Guard is to educate horse owners on their horses dietary needs in order to for them to become better horse owners. We developed the first over the counter selenium supplement in 1978.  Please read material below to learn about the critical mineral selenium. If you have questions feel free to ask our nutritionist!

  • The Crucial Mineral Selenium

    Selenium is an essential nutrient and it is very important to take a look at the way we feed and supplement this to our animals.
    Healthy Paint Horse Guard Horse

    Selenium has several important functions, including the production of antibodies for better immunity, production of thyroid hormone (thyroxine) that can affect growth rates, Vitamin E retention as well as protection against oxidative damage to cell membranes. Some key benefits of selenium for horses are:

    • Its function as a natural antioxidant
    • Role in resistance to viral infections
    • Reproduction
    • Growth
    • Protects integrity of muscle tissues
    • Involvement in immune response

    About Selenium deficiencies:

    Selenium deficiencies can show as clinical symptoms or sub-clinical.

    In clinical deficiency you can see physical problems. With sub-clinical deficiencies you don۪'t see the problems; they are expressed as poor fertility, poor disease resistance, a longer time for muscle recovery, and other problems that you cannot observe.

    English dressage horse Horse Guard supplemented

    Some of the more obvious signs of Selenium deficiency include:

    • Abortions or Retained Placenta
    • Muscular dystrophy (foals)
    • Tying up۪
    • Anorexia
    • Muscle weakness
    • Diarrhea

    When considering selenium supplementation you should know that the best way is to feed organic selenium at 3 mg per day for a 1,000 lb horse.

    What are different ways to Supplement Selenium:

    There are four ways selenium can be supplemented to a horse:

    1. Injection: This is a very poor way to administer any nutrient, especially selenium. With an injection, a horse is given a very high dose all at once which is clearly not optimal. The blood levels drop to below normal selenium and the process is repeated.
    2. Selenium in a salt mix: This is the only practical method for herds horses on pasture or free choice hay. Salt mixes are not ideal as intake varies dependent on the horse, the heat, and the amount of salt in the rest of the ration.
    3. In a Complete Feed: This can be an effective method of supplementation IF the horse owner feeds the daily recommendation. If the directions say feed 2.2 lb per 100 lbs bod y weight, you must feed 22 lbs per day to a 1,000 lb horse to get enough selenium.
    4. As a supplement top dressed on grain: This is the best method of supplementation because the horse owner knows what each horse is getting and how much. By top dressing, the horse is given a consistent daily dose which is optimal for supplementation. Horse Guard has an entire line of products with the recommended daily dose of organic selenium.

    Organic Selenium vs. Inorganic (Sodium Selenate)

    Bay Quarter Horse grazing, Horse Guard Supplements

    The other critical consideration is what kind of selenium to provide. It is important for horse owners to be aware that there are two types of selenium available. These forms are radically different from each other, even though in a products' guaranteed analysis both forms are simply listed as "selenium".

    The true identity of the selenium in the product will be in the list of ingredients as either seleno-yeast or sodium selenite (or sodium selenate).

    Selenium, in the inorganic form, selenite or selenate, is a common and inexpensive ingredient in complete feeds and supplements. This type of selenium is dangerous at levels above requirements and potentially toxic. It is less available to horses and rapidly excreted from the body. Selenite or selenite are not natural to the body and poorly processed.

    The organic form, primarily Seleno-Methionine, comes from selenium yeast and is very available to the animal. It is readily absorbed and stored in muscle tissues. The organic Selenium is the same as the horse would receive if it was able to graze on selenium-rich grasses. The horses' body recognizes it as an essential nutrient and has the ability to process and store it.

    The United States Food and Drug Administration (FDA) approved selenium yeast (organic selenium) for equine feeds in 2004 even though Sodium Selenite had been approved many years prior. It is disappointing that the FDA was slow to allow organic selenium because it is proven safer and more effective than the inorganic form which are bi-products of copper mining.

    In Japan, it is against the law to use inorganic selenium because of toxicity and lower availability. Research demonstrates the organic form, specifically selenium yeast, provides optimum selenium status for all horses.

    Organic Selenium for Peak Performance and Optimum Health

    Breeding Horses and Foals: Organic Selenium provides a much higher level of available selenium to the mare and foal. Foals are born with better selenium status, milk has higher antibody levels (more immunity). Mares expel the placenta more rapidly when they receive organic selenium. One of the symptoms of selenium deficiency is retained placenta. The fact that organic selenium speeds placenta expulsion is evidence that organic selenium is superior to inorganic selenium. Both mare and foal have big advantages when they are fed organic selenium.

    Healthy racing horse Performance Horse

    Performance Horse: Selenium is critical to performance horses. Supplementing a deficient horse will improve performance, increase stamina, and can be the difference between first and just being entered. The stress of travel and competition requires top nutrition. If you don۪'t provide for this deficiency you will certainly have lowered performance.

    Breeding Horses and Foals: Organic Selenium provides a much higher level of available selenium to the mare and foal. Foals are born with better selenium status, milk has higher antibody levels (more immunity). Mares expel the placenta more rapidly when they receive organic selenium. One of the symptoms of selenium deficiency is retained placenta. The fact that organic selenium speeds placenta expulsion is evidence that organic selenium is superior to inorganic selenium. Both mare and foal have big advantages when they are fed organic selenium.

    Older Horses: Because organic selenium is better absorbed and retained it is important for geriatric horses. The ability to metabolize nutrients declines with age. It will help to improve immunity and therefore resistance to disease.

    The form of selenium supplemented to horses is directly related to its availability and use in the body. Research demonstrates the organic form; specifically selenium yeast provides optimum selenium status for all horses.


    Comparing Selenium to Oil in a Gas Engine

    Compare selenium nutrition to a gas engine. The gas comes in the form of fiber, sugars, and fats. The horse modifies these nutrients to use or store them. When he needs energy he burns the fuel. Selenium and other minerals can be compared to the oil. The oil is there to lubricate the machine and keep it healthy. Vitamins and minerals are stored in the system and used to make the burning of energy possible in the same way oil is used in the motor.

    The car doesn۪'t use much oil, just enough to support body functions. We top off the vitamins and minerals daily because some it is naturally lost. The motor can run when it is a little low on oil. When stressed the engine that is a little low on oil breaks down. The engine will also break down if you provide too much oil. It reaches a toxic level that bogs down the machine and creates problems. Compare oil to levels of selenium.


      If you are feeding a 1000 lb horse;
    • 1 mg per day - is a low level - not enough for stress
    • 3 mg per day - correct level to handle stress
    • 20 mg per day - approaches the danger of toxicity.

    Why 3 MG Per Day?

    Healthy Horse Guard Horse

    Nutritionist recognized selenium as a dietary essential in 1957.  In 1979 it was approved as a supplement for cattle. The FDA estimates that the delays in approval of selenium cost the livestock industry over 600 million dollars in losses due to disease, reduced fertility and growth. The FDA restricted supplementation to .1ppm or 1 mg for a 1000 lb horse. This is too little for horses under stress. Research indicated that animals needed 3 times that much to stand the stress of weaning and other life events.

    In 1978, Horse Guard Inc produced the first product to be sold in stores that contained selenium. It provided 3 mg per day to a 1000 lb horse. Since that time 100,000۪s of horses have had the benefit of this level of selenium.

    In 2004 the Food and Drug Administration approved 3 mg of organic selenium per day for a 1000 lb horse. This is the level that equine nutritionists knowledgeable about selenium recommend. The basic truth is that a 1000 lb horse under no stress is sufficient receiving 1 mg of selenium per day. Horses that are under the stress of transportation, performance, breeding, foaling, or disease need 3 mg of organic selenium per day. I recommend 3 mg per day for all horses because they all will face stress at some point in life.

    Selenium Toxicity

    Acute toxicity A one time dose of at least 2000 mg on 1000 lb horse. Chronic toxicity - 20 to 50 mg per day on 1000 lb horse. Symptoms of selenium toxicity include abnormal movement, dark watery diarrhea, high temperature, weak and rapid pulse, labored respiration, bloating and abdominal pain, pale and blue mucous membranes, and dilated pupils. Most animals with acute selenium toxicity are found dead, and there is no antidote for those found alive. Livestock that feed on plants with high levels of selenium develop alkali disease so-called because plants more easily take up selenium when grown in alkali soils. Selenium toxicity is characterized by lameness, hoof malformation, hair loss, emaciation and liver damage. The mechanism behind selenium toxicity is not well understood.

    Results Speak for Themselves

    "Back in September of 2015 I had my horse's selenium level checked because he was having an issue with balance. It was low. I had been using a product with 1/3 the amount of selenium than Horse Guard (I was trying to save money). Dr. Chris Camp wanted the level to be higher. I immediately changed back to Horse Guard. I attended the seminar you hosted at Del Oeste Equine Hospital here in Eugene, OR in January of 2016. I had my horse retested. His level was now perfect!!! And his balance issue was gone. I am so impressed with how much his level grew in such a short amount of time. I really just wanted to say thank you for creating this wonderful product that keeps our horses healthy. I have always stressed vitamin use with all my horse friends and pushed the selenium, but now I have my own story to share with them as to why they need to use Horse Guard." Sincerely, Celia

  • Why Do Horses Need Selenium?

    Healthy Horse Guard Horse

    The Importance of Selenium

    Selenium has several roles in horse health, but the most well-known is as a key element in antioxidant defense, which makes it important in every cell in the body as well as in immune defense.

    The body produces radical oxygen metabolites (ROM) as a normal consequence of oxygen metabolism. Selenium-requiring enzymes such as glutathione peroxidase (GSH-Px) neutralize ROM, rendering them harmless and protecting cellular machinery from damage.

    Other basic processes requiring selenium for normal function include growth, disease defense and reproduction. Selenium-supplemented foals are known to grow better than Se-deficient foals, possible because a Se-dependent enzyme is needed to activate thyroid hormone.

    In addition, both males and females require selenium for reproductive function.

    Exercise increases oxidative metabolism markedly, which results in mobilization of tissue selenium to meet increased antioxidant demand. This explains why performances horses and human athletes have greater selenium needs than non-athletes.

    Is Organic Selenium more or less toxic than inorganic selenium?

    Although more digestible than inorganic selenium, organic selenium is actually much safer to both horses and humans. The organic selenium compounds that plants and yeast produce are nature۪s way of providing a potentially toxic element in a safe form. Seleno amino acids are absorbed from the gut via amino acid pathways, which necessarily limits excessive uptake.

    In contrast, inorganic selenium (selenite) is passively absorbed, which allows rapid and unregulated uptake of toxic levels of selenium. Organic Selenium is also much safer to handle by those mixing feeds. Sodium selenite is extremely toxic because it is absorbed through the skin. In contrast, the compounds of organic selenium are not absorbed on contact, which increases safety against the most common selenium toxicity problem: exposure to human skin.

    Selenium decreases immunity and only organic selenium allows for proper muscle recovery from exercise.

    For a long time we have believed that selenium deficiency decreases disease resistance. Selenium is as critical to horse health as any vaccination that you could give. Here is the story:

    At the University of Kentucky they fed horses a selenium deficient diet and naturally they became selenium deficient. They also monitored GPx status, an enzyme that relieves oxidative stress in muscle tissue after exercise. They found:

    Immune function assessment of the horses indicated that low selenium status was detrimental to the immune system. Also, following exercise the horses of low Se status experienced a decrease in GPx activity which did not recover within 24 hours. This occurred even though the exercise was mild with the recreational riding horse in mind. GPx activity increased post-exercise in horses supplemented with Se-yeast (organic) but decreased in the inorganic Se group (Sodium Selenate).

    This further validates the importance of supplementing organic selenium when horses are fed a selenium deficient diet.

    This information is taken from the Equine Disease Quarterly Newsletter, October 2013. It is produced by the Gluck Equine Research Center at the University of Kentucky.

  • How To Calculate Selenium In Other Feeds & Supplements

    Learn these simple facts and you will know how much and what kind of selenium you are providing to your horse. You will need to read the label of your feed to determine the type and amount or selenium that you are providing.

    Fact 1: You must supplement with selenium in the Northwest.You and your horse live in an area of critical selenium deficiency. Not supplementing with selenium is dangerous.

    Fact 2: Organic Selenium is safer and more effective then inorganic.In the guaranteed analysis of feed and supplements, both are referred to as selenium. You must look at the list of ingredients on your feed bag to tell what source the selenium is from. It is inorganic if it says sodium selenite or sodium selenite. It is organic if it says Seleno-Yeast or Seleno-Methionine.

    Fact 3: A 1,000 lb horse needs 3 mg. of Organic selenium a day. If the horse is heavier or lighter increase or decrease the selenium by the appropriate percentage. This provides enough selenium for times of stress and is very safe.

    How do you know how much selenium your horse is receiving?

    In grains or complete feeds, selenium will be listed in parts per million (PPM). PPM is a measure of concentration just like percent. It is convenient when there is only a small amount present. Percent is 1 part per one hundred. PPM is 1 part per million.

    The table below will allow you to figure out how much selenium you are providing. Find the concentration of selenium on your feeds۪ guaranteed analysis. You must feed the amount in the right column to provide the necessary 3 mg per day.

    .3 ppm feed 22 lbs
    .4 ppm feed 16.5 lbs
    .5 ppm feed 13.2 lbs
    .6 ppm feed 11 lbs per day
    .65 ppm feed 10.2 lbs per day
    .7 ppm feed 10 lbs per day
    .8 ppm feed 8.25 lbs
    .9 ppm feed 7.3 lbs
    3 ppm feed 2.2 lbs

    If you are not getting enough selenium from the feed mix, you should add selenium.Many horses will gain too much weight if you feed enough of the complete feed to provide needed vitamins and minerals. The easiest and safest way is to correct the difference is to top dress with a vitamin mineral supplement that provides organic selenium. This will allow you to provide complete vitamins and minerals even though you are not able to feed enough of the grain mix to reach optimum levels.

    Last Fact: Feeding inorganic or too little selenium is better than nothing. If you are feeding less or more than 3 mg per day, your horse will still receive some benefit. You definitely want to be sure that your horse is getting at least 1 mg. per day and less than 20 mg per day.

  • Horse Guard Funds Selenium Research

    Nutritional science really does not know enough about selenium metabolism. As a result Horse Guard has funded a selenium study at West Texas A&M. This study was conducted by Dr. Kelsey J. Nonella. The study takes selenium sufficient horses and feeds them hay from the Pacific Northwest (Central Oregon), which is extremely selenium deficient. West Texas A&M monitored the depletion of selenium in the horses blood over time. This phase was complete in Jan. 2014, making all horses significantly deficient in roughly 4 months (112 days). On day 113, the team started the repletion phase and for the next 112 days monitored the repletion phase. The horses were divided. Both groups were still fed the same extremely selenium deficient (Pacific Northwest) hay. The difference was, group 1 had 3 mg of organic selenium added to their diet (Horse Guard), while group 2 had 1 mg of organic selenium added to their diet. The results were amazing. Below is Dr. Nonella's synopsis and summary of the trail. Click on the link below for the whole dissertation.

    Synopsis: Selenium is an essential trace mineral that serves as an antioxidant, and aids in both immune function as well as thyroid hormone metabolism. The objective of this research was to evaluate the effects of Se depletion and repletion on whole blood Se concentrations and erythrocyte glutathione peroxidase (RBC GSH- Px) activity.

    Summary: Read more about the details on Dr. Kelsey's doctoral research in her dissertation. She fed horses Northwest hay without selenium supplementation for four months, and then added selenium supplementation for four additional months. During the depletion and repletion she monitored the status of selenium in horses. She found that by the end of depletion, horses were close to clinically selenium deficient, and that four months of selenium supplementation was not enough time to get the horses back to adequate selenium levels. This drives home the point that it is critical to continuously supplement your horse to ensure optimal health.


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