MSD Manual

Please confirm that you are a health care professional

honeypot link
Pet Owner Version

Introduction to Blood Disorders of Horses


Susan M. Cotter

, DVM, DACVIM, Cummings School of Veterinary Medicine, Tufts University

Reviewed/Revised Mar 2019 | Modified Oct 2022
Topic Resources

Blood cells form and develop mostly in the bone marrow, that is, the tissue located in the cavities of bones. Blood performs a variety of important functions as it circulates throughout the body. It delivers oxygen and vital nutrients (such as vitamins, minerals, fats, and sugars) to the body’s tissues. It carries carbon dioxide to the lungs to be exhaled and waste products to the kidneys and liver to be eliminated from the body. It transports hormones, which are chemical messengers, to various parts of the body, allowing those parts to communicate with each other. Blood also includes cells that fight infection and platelets that control bleeding.

There are 3 cellular elements of blood: red blood cells, white blood cells, and platelets. Basically, red blood cells supply the body with oxygen; white blood cells protect against infection; and, platelets start the formation of blood clots.

Blood components

Blood components

Blood disorders are quite diverse. They can occur as normal responses to abnormal situations; for example, a significant increase in the number of white blood cells in response to an infection or disease. They may also occur as primary abnormalities of the blood; for example, a deficiency of all cellular elements of the blood due to bone marrow failure. Furthermore, abnormalities may be quantitative (too many or too few cells) or qualitative (abnormalities in the way cells function). It is helpful to understand what the names of some blood disorders mean, as they often provide a description of the disorder itself (see Suffixes table below). Like people, horses have different blood groups Blood Groups and Blood Transfusions in Horses Blood groups are determined by the presence or absence of certain proteins or sugars found on the red blood cell membrane. The number of blood groups varies among domestic species. Normally... read more or types. Researchers have identified 8 blood types in horses: A, C, D, K, P, Q, U, and T. Groups A, C, and Q are considered the most important.


For More Information

Also see professional content regarding blood and blood disorders Hematopoietic System Introduction .

quiz link

Test your knowledge

Take a Quiz!