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4 min read

Selenium for Dogs


By Jasmine Sawatzky

Published: 05/19/2023, edited: 05/24/2023

Reviewed by a licensed veterinary professional: Dr. Linda Simon, MVB MRCVS

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Selenium is a trace mineral found in soil. From the soil, this essential nutrient works its way into the food we eat and the water we drink. How much selenium food and water contains depends greatly on the location and the soil conditions. In many areas, selenium levels are low or depleted due to improper farming practices. Fortunately, dogs only need a very small amount, but this microelement is still essential for the function of their metabolism, thyroid, synthesis of DNA, and for reproduction. It can even play a key role in treating cancer. 

Dogs that are fed commercial dog food should already have a balanced intake of selenium, but for dogs on homemade diets, it may not always be the case. What exactly does selenium do, and how can you be sure your dog is getting enough of this essential mineral? Let’s dig a little deeper! 

Brown pit bull smiling with eyes closed and tongue out - selenium for dogs


Selenium contributes to a surprising amount of functions in a canine’s body. This tiny powerhouse is an essential component of many different enzymes and proteins called selenoproteins. Most of the selenium is stored in a dog’s muscle tissue, but the highest concentration is found in the thyroid gland, where it helps with the function of hormones. Recently, it has been shown that there is a link between selenium deficiency and hypothyroidism. 

Selenium also plays an important role in a male dog's reproductive health. In one study, supplementation with selenium and vitamin E improved sperm quality in dogs with lowered fertility and even helped four infertile dogs to mate successfully. 

Selenium is even used to help fight cancer! When ingested, selenium is converted into an enzyme that is a powerful antioxidant, called glutathione peroxidase. These enzymes protect cells from damage by free radicals. Because of these anti-cancerous properties, selenium is often used in dogs with cancer, or even for cancer prevention in older dogs. However, never treat your dog at home with a selenium supplement without consulting a vet first, because too much selenium would be counter-productive to treating cancer and possibly dangerous. 

Other health benefits of selenium include preserving tissue elasticity, increasing the effectiveness of vitamin E, and reducing inflammation. 

The Association of American Feed Control Officials recommends a minimum of 0.35 mg of selenium per kg of your dog's body weight. The maximum limit is set to 2 mg per kg. At this time, the recommended intake is the same regardless of the dog's breed and age. 

a collage of several foods containing selenium

Food sources

Selenium can be consumed in its organic form or inorganic form. The organic form is mostly found in meats and other natural whole foods. Its inorganic form is usually what's used as a supplement in commercial dog food. 

In a study that evaluated 37 commercial dog foods, both wet and dry, the minimum requirements of selenium were met. The only difference was the dog foods with seafood ingredients had slightly higher levels of selenium. Overall, all commercial dog food manufacturers should be following the recommendations for minimal and maximal selenium levels. 

If your dog is on a homemade diet, or your vet recommends more organic selenium, there are plenty of tasty ways to consume it in its natural form. Here is a list of some of the top selenium food sources and how many micrograms they contain: 

  • Brazil nuts, dried (1 ounce) -¬†544 mcg
  • Canned tuna, oil drained (3 ounces) -¬†63 mcg
  • Beef, cooked (3 1/2 ounces) -¬†35 mcg
  • Turkey, cooked (3 1/2 ounces) -¬†32 mcg
  • Chicken breast, cooked (3 1/2 ounces) -¬†20 mcg
  • Egg (1 medium) -¬†14 mcg
  • Cottage cheese, low fat (1/2 cup) -¬†12 mcg
  • Brown rice, cooked (1/2 cup) -10 mcg

Other food sources of selenium include mushrooms, various cheeses, liver, oats, yogurt, spinach, bananas, and lentils. 

Signs of selenium deficiency in dogs

Nowadays, vets don't generally encounter clinical signs of selenium deficiency, but it can be subclinical. This means that there may not be signs and symptoms that are detectable by physical examination or laboratory tests. Subclinical deficiency seems to affect, for example, male fertility or recovery from parasitical diseases.

Some other subclinical signs of a deficiency in dogs include: 

Treatment of selenium deficiency

If your dog is experiencing a selemiun deficiency, your vet may recommend selenium supplements. They may also look at their diet and suggest a food with better levels of selenium. 

Signs of selenium overdose in dogs

Unfortunately, some of the signs of a selenium overdose in dogs are very similar to the signs of a deficiency. The symptoms are pretty vague and could have countless causes, so it's best to take your pup to the vet so they can make a proper diagnosis and treatment plan. 

Signs of chronic selenium toxicity in dogs can include: 

dark brown Labrador Retriever dog being handed a pill

Selenium supplements for dogs

The most reliable method for a veterinarian to check the selenium status of a dog is by measuring serum or plasma levels. Based on this, the vet will be able to decide if your dog needs a supplement. 

The goal of supplementation would be to raise the amount of selenium in your dog to normal levels. Selenium supplements may also prevent cardiovascular disease, support with cancer treatments, thyroid disease, and cognitive decline. If your dog already has a balanced, high-quality diet and consumes a proper amount of selenium, then a supplement would be ineffective and maybe even harmful. 

Selenium can be administered by mouth in capsule form, or as an injection in the veterinarian’s office. It's often given with vitamin E because this makes it more effective. 

An average dose of supplemental selenium in standard dog foods is 0.11mg per kg of adult dog weight. Your veterinarian may prescribe selenium in a lower or higher dose based on the condition being treated, the dog’s age and clinical appearance, and test results. 

As you can see, selenium serves a crucial role in the canine body. While deficiencies are unlikely, they can happen if a dog eats an unbalanced diet.

Thinking about starting your dog on a supplement? Chat with a veterinary professional today to discuss your dog's nutrition and more!

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