10/11/2026
Know Your Minerals
🐴 𝐒𝐄𝐋𝐄𝐍𝐈𝐔𝐌: 𝐀 𝐋𝐈𝐓𝐓𝐋𝐄 𝐆𝐎𝐄𝐒 𝐀 𝐋𝐎𝐍𝐆 𝐖𝐀𝐘!
The next instalment in our series on minerals and what they do for horses is all about SELENIUM.
Selenium is an essential trace mineral, meaning horses only need very small amounts, but it plays some pretty important roles in keeping them healthy.
💪𝐖𝐇𝐘 𝐃𝐎 𝐇𝐎𝐑𝐒𝐄𝐒 𝐍𝐄𝐄𝐃 𝐒𝐄𝐋𝐄𝐍𝐈𝐔𝐌?
One of selenium's most important jobs is helping protect the body's cells from oxidative damage.
It works alongside Vitamin E as part of the body's antioxidant defence system, helping protect muscles and other tissues from damage caused by free radicals.
Selenium also contributes to:
✔️ Normal muscle function
✔️ Healthy immune system function
✔️ Thyroid hormone metabolism
✔️ Protection of muscle and other body tissues from oxidative damage
🐎𝐒𝐄𝐋𝐄𝐍𝐈𝐔𝐌 & 𝐇𝐎𝐑𝐒𝐄𝐒 𝐓𝐇𝐀𝐓 𝐓𝐈𝐄 𝐔𝐏
Selenium is particularly important for muscle health. Working alongside Vitamin E, it helps protect muscle cells from oxidative damage. If a horse is deficient, this may contribute to muscle problems and make muscle tissue more vulnerable to damage.
For horses that experience tying-up (exertional rhabdomyolysis), checking selenium and Vitamin E status may be worthwhile. However, not every horse that ties up is selenium deficient. There can be several underlying causes, including genetics, exercise and feeding management, so simply adding more selenium isn't the answer. Getting the diet and underlying cause investigated is important.
🔍 𝐇𝐎𝐖 𝐃𝐎 𝐘𝐎𝐔 𝐊𝐍𝐎𝐖 𝐈𝐅 𝐘𝐎𝐔𝐑 𝐇𝐎𝐑𝐒𝐄 𝐈𝐒 𝐆𝐄𝐓𝐓𝐈𝐍𝐆 𝐄𝐍𝐎𝐔𝐆𝐇?
Selenium deficiency can be difficult to recognise because the early signs aren't always obvious.
Possible signs include:
• Muscle weakness or stiffness
• Poor coordination or difficulty moving
• Muscle trembling
• Difficulty swallowing
• Poor suckling ability in affected foals
• In severe cases, breathing difficulties and impaired heart function
In young foals, severe deficiency can cause significant muscle damage, including damage to the heart muscle. This condition is known as White Muscle Disease.
It's important to remember that these symptoms can also be caused by other conditions. You cannot reliably diagnose selenium deficiency just by looking at your horse.
A veterinarian can arrange blood testing to assess selenium status, and feed or pasture analysis can help identify whether the diet is providing enough.
⚠️ 𝐂𝐀𝐍 𝐀 𝐇𝐎𝐑𝐒𝐄 𝐇𝐀𝐕𝐄 𝐓𝐎𝐎 𝐌𝐔𝐂𝐇 𝐒𝐄𝐋𝐄𝐍𝐈𝐔𝐌?
Absolutely! And this is where we need to be particularly careful.
Selenium has a relatively narrow safety margin. Too much can be toxic, particularly when several fortified feeds and supplements are being combined.
Chronic selenium toxicity, known as selenosis, can cause:
• Hair loss, particularly in the mane and tail
• Weak, cracked or deformed hooves
• Separation or sloughing of the hoof wall around the coronary band
• Reduced reproductive performance
Severe acute poisoning can cause serious cardiovascular and neurological problems and can be life-threatening.
This is why adding extra selenium without knowing what your horse is already receiving is not a good idea.
🌱 𝐖𝐇𝐄𝐑𝐄 𝐃𝐎𝐄𝐒 𝐒𝐄𝐋𝐄𝐍𝐈𝐔𝐌 𝐂𝐎𝐌𝐄 𝐅𝐑𝐎𝐌?
Horses obtain selenium through their forage, pasture, hay and manufactured feeds.
The amount in pasture and hay depends largely on the selenium content and availability in the soil where the plants were grown. This can vary considerably between regions.
Some areas have naturally selenium-deficient soils, while others may have higher levels.
Commercial feeds, mineral mixes and supplements may also contain added selenium, so it's important to consider the total amount your horse is receiving.
🤔 𝐒𝐎, 𝐒𝐇𝐎𝐔𝐋𝐃 𝐘𝐎𝐔 𝐒𝐔𝐏𝐏𝐋𝐄𝐌𝐄𝐍𝐓 𝐒𝐄𝐋𝐄𝐍𝐈𝐔𝐌?
Not necessarily!
The aim is to provide enough selenium to meet your horse's requirements without exceeding them.
For a typical 500 kg adult horse, the estimated daily requirement is around 1 mg of selenium per day from the total diet. This includes selenium already present in forage, hay and fortified feeds.
Before adding a selenium supplement, check what is already in your horse's diet and seek veterinary or equine nutrition advice if you're unsure.
Remember: More isn't better when it comes to selenium!
💬 Do you know whether your horse's current feed or supplement contains selenium? Have you ever had your pasture or hay tested?
