Blood types were discovered only in the early 20th century. Previously, in the 'dark' times, when there were serious losses, people could receive blood transfusions from pigs or other animals, but this often led to fatal outcomes. Today we know that blood transfusions are only possible between compatible groups. How different is the blood of animals from that of humans?
Blood type represents the antigenic characteristics of red blood cells, based on the types of carbohydrates and proteins in their membranes. If blood types do not match, the body will react aggressively to such blood. In humans, there are several antigen systems, a total of 36, but blood type is most often determined by the ABO system (O I, A II, B III, and AB IV) and the Rh factor (-/+). Animals have their own systems that do not overlap with those of humans.
For example, dogs have seven main blood groups, each with its own Rh factor (a total of about 13 blood groups have been identified in dogs). All of them are varieties of DEA — the dog antigen that predominates in their red blood cells. The DEA system includes groups: 1.1, 1.2, 3, 4, 5, 6, and 7. Often, representatives of the same breed have the same group; for instance, 60% of greyhounds have negative DEA 1.1. Interestingly, 98% of dogs are compatible with DEA 4, while only 42% are compatible with DEA 1.1. However, scientists continue to discover new blood groups in dogs; it was recently established that Dalmatians have their own group — Dal.
As for cats, they have only two antigens — A and B (which differ from human ones). There are no universal donor blood groups in cats, but the vast majority (about 90%) of domestic cats have blood type A, while rarer purebred breeds often have type B. Blood type AB is also occasionally found, but extremely rarely.
The blood groups of horses are also well studied. These animals have 30 different groups, representing combinations of 8 antigens (A, C, D, K, P, Q, U, and T, the latter is still under investigation). Cows have 11 main blood groups (A, B, C, F, J, L, M, R, S, T, and Z), with group B including over 60 different antigens.
Each animal has its own unique system and set of antigens, making blood transfusions between animals (and humans) risky. Certainly, when your pet requires a transfusion, a blood type test will be conducted, and a suitable donor will be selected. Interestingly, like humans, pets can also become voluntary donors. Typically, no more than 22 milliliters per kilogram of body weight is taken from dogs, and no more than 15 milliliters per kilogram from cats.
