According to Dr William Ray Fullmer, a veterinarian practicing in Oregon, one of the most under utilized areas of veterinary practice is transfusion medicine. A transfusion can mean the difference between life and death for animals.
Transfusion medicine involves the administration of blood or plasma. This can be done in most species, but are mainly performed in horses, dogs, cats, llamas, and alpacas.
In general transfusions are administered for the following reasons; surgery, trauma, or to mothers after giving birth. Also for chronic blood loss for such things a stomach ulcer, and following red blood cell destruction due to blood borne parasites or immune destruction of red blood cells. Generally a blood transfusion is suggested if the packed cell volume is 10% or less.
Plasma administration is used successfully in several disease processes. Benefits of plasma transfusion include maintenance of vascular pressure and vascular transport capabilities, supplementation of antibodies, and addition of chemicals that decrease tissue proteases, and supplementation of blood clotting factors.
As in humans, animals have different blood proteins in their red blood cells. The number of combinations in horses is estimated at 40,000 although many of these groups may be extremely rare.
The good news about horses is that it is generally safe to transfuse a horse that hasn't received a previous transfusion. This is because even though there are many blood proteins they are fairly weak and don't stimulate much of a reaction with an initial transfusion.
If a second transfusion is given however, the chance of a reaction is more likely because the body will have had time to develop a reaction to the proteins from the first transfusion
Many veterinary schools keep horses and llamas that serve as blood donors. There are also some private companies and even some large farms that collect, prepare and sell llama and horse blood products.
Your veterinarian will be familiar with these resources if the need arises for a blood or plasma transfusion. Don't hesitate to ask your veterinarian if you have any questions.