Dr. Jeske Noordergraaf

I enjoy asking kids what color blood is.  Do you know?  Frequently the answer is "blood is blue inside us and red when it hits the air".  Blood carries oxygen in our body so this really doesn't make sense.  Blood is red with arterial blood being brighter and venous blood being darker.  Our blood vessels have a bluish appearance through our skin but just as water going through PVC piping isn't white, blood isn't blue.

An adult horse has about 32 liters of beautiful red blood circulating throughout it's body.  Hemorrhage or bleeding is severe and causes shock when 30% or 10.8 liters is lost rapidly.  It is generally very hard to access how much blood a horse has lost  but when the following signs are seen, be concerned. Rapid breathing and a rapid heart rate along with pale gums and prolonged jugular filling happen initially and with continued bleeding, exercise intolerance, muscular weakness and collapse can follow.  The spleen, which stores blood, will contract and release red blood cells into the circulation as the horse tries to recover.  Common causes of bleeding include traumatic events such as lacerations.  Nasal surgery or guttural pouch fungal infections can also be the cause along with spontaneous middle uterine artery hemorrhage in a mare who has just foaled.  Direct pressure is the best way to stop bleeding.  If your horse has a laceration which is bleeding, use lots of padding and leave it on until a veterinarian can arrive to treat the wound.  Keep the horse quiet in a stress free environment. 

Blood has many jobs in our body.  It supplies cells with water, electrolytes, nutrients, and hormones and then removes the waste products.  The different cells types in the blood have very specific jobs.  The red blood cells supply the oxygen.  The white blood cells protect against foreign organisms and antigens.  Platelets cause clotting.  We know the normal number of each of these types of cells in every species and that either too many or too few can indicate a problem. 

Veterinarians like to draw blood from horses because it gives us an idea of what is going on inside the horse at that moment.  We can analyze how the organs are functioning and how the immune system is working.  Common tests that are run on blood include: the Coggins test for equine infectious anemia (EIA), and titers for other diseases including EVA, Rotavirus, and Strangles to just name a few.  The complete blood count (cbc) test tells us how the immune system is working and whether the horse is anemic (doesn't have enough red blood cells) or is dehydrated.  A chemistry panel measures organ function, muscle enzymes and electrolytes.  DNA testing is now commonly done on hair follicles to determine if a horse has the genetic potential to develop a disease such as HYPP but a blood test will measure if the horse has an active episode. 

What is pus?  Sometimes when we culture an abscess, we are unable to grow an organism.  That is because the white blood cells are doing their job and ingesting the bacteria and the pus is actually all those white blood cells.  The body is trying to heal itself.  Antibiotics may be necessary if the infection is severe or generalized but if we didn't have an immune system to do the necessary work, we would be in bad shape.  We would need to live in a bubble with our horse. 

The blood vessels in our bodies are the highways, always busy but organized.  So remember that blood is red and impress your friends with your blood knowledge.