Horses have over thirty blood groups but only eight of them are considered major systems. These are A, C, D, K, P, Q, T and U. Of the eight, seven systems are generally recognized (T excluded). In equine blood typing, the systems are written with an upper case letter with a lower case letter to mean the factors or antigenic sites hence A (a, b, c, f, g), Ca, D (a, b, c, e, f, g, h, i, k, l, n, o, p), Ka, P (a, b, c, d), Q (a, b, c), and Ua. The antigens present in the red blood cells determine the horses’ blood group systems.

Unlike humans and even other animals, equine blood groups can be present in one of divers forms. A horse, for instance, of type A blood may mean type Aa+, Aa-, Ca+, Ca- Qa+, Qa-, etc.

Equine blood typing is important to distinguish blood match in transfusion and compatibility in breeding and to prevent equine neonatal isoerythrolysis (NI), a condition whereby foals develop hemolytic anemia after ingestion of the mare’s colostrums.

Of the equine blood groups, a number have been found to have NI reactions. This includes Ab, Dc, Pa, Ua, Aa and Qa, of which the last two equine blood groups are considered to have the “most severe immunologic reactions.” These two are said to have been responsible for almost 90% of all equine NI cases. Breeds commonly associated with NI are the Standardbred and Thoroughbred because these two have higher Aa and Qa antigens.

Foals with NI can be noticed through the following symptoms: weakness, icterus of the sclera and mucous membranes, which may mean hemolysis in the horse, red-brown discoloration of the urine (can mean myoglobinuria, hemoglobinuria, or hematuria), yellow discoloration of plasma (suggests hemoglobinuria), gasping and depression. If not recognized and treated soon, the foal may die.

The reason why it is important for horse owners and breeders to know their equine blood types is that lack of knowledge may cause mismatch blood transfusion or mismatch cross breeding. In many instances acute hemorrhage in the horse is treated with whole blood transfusion. Although most horses lack antibodies, which can mean a safe and successful blood transfusion, laboratories still perform a hemagglutination mismatch to find out possible incompatibilities to protect any incidence of NI in the future foals of the mare.

For fluid loss or colloid replacement, a horse can be treated by plasma transfusion. Here it is also important to type the horse to avoid any problems.

There are many ways to keep your horses from becoming sick but everything has to start from becoming aware of your equine blood types, especially if you are planning to have them mate. Always, NI happens due to incompatible mating.

This Article is written by Lena Butler, contributor of  Health & Drug Testing Information Center.

Posted under Animal Testing
Tags: equine blood groups, equine blood types, equine neonatal isoerythrolysis.