General Information:

Horse Blood Group Factors

Similar to humans and other mammals, horses have a large number of blood groups, each with many variants (factors). The most important of these in the horse are the Aa, Qa, Qb, and Qc factors.

Blood group testing allows animals to be paired who will have compatible blood group factors. Neonatal Isoerythrolysis (NI) can occur when an incompatible breeding and exposure to a foreign factor leads a mare to produce antibodies against this factor in the future which can harm the foal. Approximately 90% of NI cases are due to the Aa, Qa, Qb, and Qc factors.

Available Tests:

  • H300 – Pre-breeding testing
  • H301 – Pre-foaling testing
  • H302 – NI testing
  • H303 – Colostrum testing

For further information about the tests and ordering see bottom.

Neonatal Isoerythrolysis (NI)

Neonatal Isoerythrolysis (NI) is a potentially fatal condition in foals that occurs when antibodies in the mother’s first milk (colostrum) attack the red blood cells of the foal. This can cause severe disease including anemia, jaundice, organ damage, and if not diagnosed immediately, death. This situation can usually be avoided by not breeding mares and stallions with incompatible blood types.

There is rarely a problem with the first foal, but the potential for NI increases each time a mare is bred to a blood group-incompatible stallion. The prevalence of NI is dependent upon the frequency of blood group factors in a breed population – the chance that a male and female will be incompatible for the factor.

Risk factors for Neonatal Isoerythrolysis

Test information:

Important! Samples for this test need to be processed very quickly, therefore it is very important that you inform us about the test(s) you want to order BEFORE you acutally place the order. Shipping should be as fast as possible. Do not ship before weekends! Please contact us via phone or email.

Test: H300 - Pre-breeding testing

All breeding stock can be blood group tested for the Aa, Qa, Qb, and Qc and other factors. This can be done at any time, and this information will then be known for life. Blood group factor-compatible breedings can be planned which will minimize the chance of a foal being affected by NI.


Used for:


  • Knowing what blood group profiles should be avoided in a mate to avoid producing a foal with NI.
When: anytime

Substance: 5mL blood

Tube(s): EDTA (purple top)

Storage: 4°C

Cost: 60€ (excl. VAT)

Time: 10 – 20 days

Test: H301 - Pre-foaling testing

Within two weeks of foaling (when her milk starts to come in) the mare’s serum can be tested to see if the antibody levels will be high enough to affect the foal. If so, the foaling must be attended and the foal should be fitted with a muzzle and prevented from drinking any of the mare’s colostrum; a veterinarian can advise when her regular milk comes in and the foal may drink safely.


Used for:


  • Finding out if a foal should be prevented from drinking the colostrum.
When: max. 2 weeks before foaling

Substance: 8-10mL serum

Tube(s): empty

Storage: 4°C or-20°C

Cost: 42€ (excl. VAT)

Time: 5 – 7 days

Test: H302 - NI testing

A foal showing symptoms of NI (lethargy, jaundice, fever, weakness) in the first week of life requires urgent veterinary care. Blood and serum from the foal, along with serum from the mare should be tested to make a diagnosis of NI. If the mare or stallion were not previously blood group tested, their blood groups should also be tested to verify the diagnosis and to be able to plan future breedings.

Used for:


  • Knowing if the Veterinarian should follow protocol for treating NI, blood group factors to avoid in future breeding (of foal, and of parents).
When: as soon as foal shows symptoms


  • Foal: 5mL blood and 8 – 10mL serum
  • Mare: 8 – 10mL serum
  • Stallion: 5mL blood

Tube(s): EDTA (blood), empty (serum)

Storage: 4°C

Cost: 200€ (excl. VAT)

Time: 4 – 7 days

Test: H303 - Colostrum testing

Colostrum should be submitted for antibody testing before banking to ensure that it does not contain antibodies that could cause NI in supplemented foals.


Used for


  • Finding out if colostrum will be safe for foals to drink.
When: before banking

Substance: 3 – 5mL

Tube(s): empty

Storage: -20°C

Cost: 42€ (excl. VAT)

Time: 5 – 7 days

Discounts: We offer substantial discounts for breed clubs and club members for all of our testing services. Bulk orders may also qualify for reduced prices. Contact us for more information!