Equine Blood Typing
Horses have 8 different red blood cell groups or systems, which are named A,
C, D, K, P, Q, U, and T. The first 7 systems are internationally recognized.
Each system corresponds to a particular gene for which two or more alleles exists.
The blood group genes produce surface molecules that contain antigenic sites
known as factors. Over 30 different factors have been identified. The blood
groups are named with an upper case letter to denote the system and a lower
case letter to designate the factor (antigen). There are variable numbers of
factors for each blood group. The VMTH Hematology laboratory types for the blood
factors: A (a,b,c,f,g), Ca, D (a,g,k), Ka, P (a,b), Q (a,b,c), Ua, V, and W.
Blood typing is useful in selecting blood donor horses for transfusions and
to determine
mare/stallion compatibility before
breeding to predict the potential for
neonatal isoerythrolysis
(NI). Historically blood typing has been used for parentage verification,
but has been replaced by DNA typing.
Blood Transfusions
Whole blood transfusions are useful in the treatment of acute hemorrhage in
the horse. At the UC Davis VMTH patients are blood typed and antibody screened
to find an appropriate donor match prior to blood transfusion. We do not recommend
whole blood transfusions without knowing the blood type of the recipient. Many
veterinary laboratories are able to perform a simple hemagglutination crossmatch
that should identify a large percentage of potential incompatibilities. The
majority of horses lack naturally occurring antibodies, so a first whole blood
transfusion is usually without consequence. Whenever a mare is given a whole
blood transfusion, she is potentially being sensitized to blood group factors
that may lead to NI problems in future foals.
Plasma Transfusions
Often a transfusion is needed to restore fluid loss or colloid replacement,
but the red blood cells are not essential. In this case, a plasma transfusion
may fulfill the clinical requirements. Plasma can be collected and stored frozen
to administer when needed. Potential plasma donors should be positive for the
blood factors Aa and Ca. Horses that are negative for these factors usually
have naturally occurring antibodies (anti-Aa or anti-Ca) or may eventually develop
these antibodies.
For either a potential whole blood or plasma donor a
blood
type and antibody screen is indicated.
Blood sample submission information
Blood Factor Frequencies
| |
A system |
C system |
Q system |
U system |
K system |
| BRED |
Aa+ |
Aa- |
Ca+ |
Ca- |
Qa+ |
Qa- |
Ua+ |
Ua- |
Ka+ |
Ka- |
| Thoroughbred |
98% |
2% |
83% |
17% |
85% |
15% |
18% |
82% |
5% |
95% |
| Arabian |
97% |
3% |
97% |
3% |
37% |
63% |
38% |
62% |
0% |
100% |
| Standardbred |
81% |
19% |
83% |
17% |
1% |
99% |
46% |
44% |
54% |
46% |
| Morgan |
81% |
19% |
90% |
10% |
1% |
99% |
46% |
54% |
1% |
99% |
| Quarter Horse |
74% |
26% |
94% |
6% |
32% |
68% |
44% |
56% |
8% |
92% |
| Paso Fino |
74% |
26% |
60% |
40% |
15% |
85% |
57% |
43% |
0% |
100% |
| Peruvian Paso |
78% |
22% |
93% |
7% |
4% |
96% |
55% |
45% |
5% |
95% |
| Tennessee Walking Horse |
70% |
30% |
93% |
7% |
3% |
97% |
88% |
12% |
4% |
96% |