Blood type (non-human)
Animals and bacteria have cell surface antigens referred to as a blood type. Antigens from the human ABO blood group system are also found in apes and old world monkeys, which have inherited the same system. Other animal blood sometimes agglutinates (to varying levels of intensity) with human blood group reagents, but the structure of the blood group antigens in animals is not always identical to those typically found in humans. The classification of most animal blood groups therefore uses different blood typing systems to those used for classification of human blood.
Simian blood groups
Two categories of blood groups, human-type and simian-type, have been found in apes and monkeys and can be tested by methods established for grouping human blood.
Rhesus blood group
The Rhesus system is named after the Rhesus monkey, following experiments by Karl Landsteiner and Alexander S. Wiener, which showed that rabbits, when immunised with Rhesus monkey red cells, produce an antibody that also agglutinates the red blood cells of many humans.
Chimpanzee blood group systems
Data on blood groups of chimpanzees, baboons and macaques. Two complex chimpanzee blood group systems, V-A-B-D and R-C-E-F systems, proved to be counterparts of the human MNS and Rh-Hr blood group systems, respectively. Two blood group systems have been defined in Old World monkeys: the Drh system of macaques and the Bp system of baboons, both linked by at least one species shared by either of the blood group systems.
Canine blood groups
Over 13 canine blood groups have been described. Eight DEA (Dog Erythrocyte Antigen) types are recognized as international standards. Of the DEA, DEA 4 and DEA 6 appear on the red blood cell of ~98% of dogs. Dogs with only DEA 4 or DEA 6 can thus serve as blood donors for the majority of the canine population. Any of the DEA may stimulate an immune response in a recipient of a blood transfusion, but reactions to DEA 1.1+ are the most severe.
The most important canine blood type is DEA 1.1. Dogs that are DEA 1.1 positive (33 to 45% of the population) can be considered to be universal recipients - that is, they can receive blood of any type without expectation of a life-threatening Hemolytic Transfusion Reaction ("HTR"). Dogs that are DEA 1.1 negative can be considered to be universal donors. Blood from DEA 1.1 positive dogs should never be transfused into DEA 1.1 negative dogs. If it is the dog's first transfusion the red cells transfused will have a shortened life due to the formation of alloantibodies to the cells themselves and the animal will forever be sensitized to DEA 1.1 positive blood. If it is a second such transfusion, life-threatening conditions will follow within hours. In addition, these alloantibodies will be present in a female dog's milk (colostrum) and adversely affect the health of DEA 1.1 negative puppies.
Feline blood groups
The commonly recognized system of feline blood designates cats as A, B, or AB. The vast majority of cats in the United States are Type A, but the percentage of Type B cats increases in other countries, such as Australia. In a study conducted in England, 87.1% of non-pedigree cats were type A, while only 54.6% of pedigree cats were type A. Type A and B cats have naturally occurring alloantibodies to the opposite blood type, although the reaction of Type B cats to Type A blood is more severe than vice versa. Based on this, all cats should have a simple blood typing test done to determine their blood type prior to a transfusion or breeding to avoid the haemolytic disease (or neonatal isoerythrolysis). It is also important to check donor cats for FeLV/FIV status.
Equine blood groups
There are eight major recognized blood groups in horses. Seven of them, A, C, D, K, P, Q, and U, are internationally recognized, with an eighth, T, which is primarily used in research. 
Breeding a mare to a stallion with a different blood type, usually Aa or Qa blood, risks neonatal isoerythrolysis if the foal inherits the blood type of the stallion. This can also occur if a mare is bred to a jack, due to donkey factor. This immune-mediated disease is life-threatening and often requires transfusion.
Ideally, cross matching should be performed prior to transfusion, or a universal donor may be used. The ideal universal whole blood donor is a non-thoroughbred gelding that is Aa, Ca, and Qa negative. If this is not available, a gelding, preferably of the same breed as the patient, may be used as a donor, and cross matching may be crudely accessed by mixing donor serum with patient blood. If the mixture agglutinates, the donor blood contains antibodies against the blood of the patient, and should not be used.
Bovine blood groups
The polymorphic systems in cattle include the A, B, C, F, J, L, M, S, and Z polymorphisms.
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