Your horse’s blood

Your horse’s blood is made up of red blood cells, white blood cells, platelets and plasma. Blood has many important roles including…

• the transport of oxygen around your horse’s body
• the removal of waste products including carbon dioxide, lactic acid and urea
• to transport nutrients, hormones and other substances
• to transport white blood cells and antibodies to fight infection
• to regulate your horse’s temperature

Red blood cells
These are circular cells that contain a substance called haemaglobin, which attaches to oxygen and carbon dioxide to enable the blood cells to carry them around the body. Red blood cells are made in the bone marrow and released into the blood stream once they are mature. They can also be stored in the spleen.

White blood cells
These cells are responsible for fighting off infection. They are split into two types – granulocytes (called this because they contain granules) and agranulocytes (without granules). Granulocytes include neutrophils, which fight off bacterial infection, eosinophils, which fight off parasitic infection, and basophils, which respond as part of an allergic reaction. Agranulocytes include lymphocytes, which produce antibodies, and monocytes, which turn into macrophages that fight off infection by engulfing the foreign cells and removing them from the circulation.

Platelets
These cells form clots to stem bleeding. They circulate in the blood with the red and white blood cells, and are activated at the site of injury. They react with fibrinogen to form fibrin. Fibrin lays down strands to create a mesh over the wound, which forms the beginnings of a blood clot.

Plasma
This is the fluid that all of these cells are suspended in. It also contains water, proteins, and all of the remaining vital substances and waste transported by the blood.

In the April issue of Horse&Rider, we took an in-depth look at how your horse’s cardiovascular system works.