Your horse’s red blood cells are formed in the blood marrow. Their job is to carry oxygen to cells throughout the body. When your horse is low on red blood cells, either because their body is not making enough of them or the red blood cells have been lost or destroyed due to injury or illness, the horse becomes anemic. Anemia can have a serious impact on your horse’s health and well-being.

Symptoms of Anemia In Horses
A horse experiencing sudden, acute anemia, such as from excessive blood loss, they may go into shock, meaning their blood pressure will have dipped. They may have an increased heart rate, their gums may be pale, and they may also be jaundiced.
Horses with chronic anemia will have developed the condition over time, so their body will have had time to adjust. As it worsens, you may notice decreased energy and performance. They may also have pale gums. Over time, you might notice poor coat quality and unexpected weight loss.
All of these symptoms can point to anemia or another serious condition, so it’s important that you work your veterinarian to find out the underlying cause.

Why Do Horses Become Anemic?
Humans prone to anemia are often advised to take an iron supplement, but the this is not the best advice for an anemic horse. Iron deficiency is not common in horses, though other dietary deficiencies can be a contributing factor.
There are two main types of anemia in horses: regenerative and non-regenerative. Regenerative anemia occurs with excessive blood loss from an injury or a gastric ulcer, or when red blood cells are damaged by parasites, an infection, or an immune system disorder.
Equine infectious anemia (EIA) is related to the virus that causes HIV in humans. It causes the immune system to attack red blood cells. It’s transmitted from horse to horse through biting flies or with contaminated medical equipment. Some horses are lifelong asymptomatic carriers, others die from acute symptoms, while others survive symptoms that typically subside in about 12 months, after which they remain lifelong carriers of the virus. There is no vaccine or cure, though it can be prevented with routine Coggins testing and by limiting your horse’s exposure to biting flies.
Blood parasites, such as babesiosis, can also cause anemia. Babesiosis is transmitted between horses through ticks. The parasitic infection can be prevented by limiting your horse’s exposure to ticks. Symptoms generally last about eight days. If the horse survives, they may make a full recovery, or they may suffer from chronic infection and may be a carrier for years.
Ingestion of poisonous plants or other toxic substances can cause long-term anemia that may develop slowly with repeated exposure.
With non-regenerative anemia, your horse’s bone marrow is not making enough red blood cells.
Though not common in horses, a deficiency in copper, iron, B-vitamins, or protein can make it harder for the body to make blood cells. A blood count from your vet can determine if your horse has a dietary deficiency.
Bone marrow disorders, leukemia, liver disease, and Cushing’s disease can all cause non-regenerative anemia. Kidney failure due to use of illegal performance drugs in racehorses can also put horses at risk.
If your horse has symptoms of anemia or otherwise seems unwell, contact your veterinarian right away.