Genetic Defects

Where the information is available, whether an animal is free of a genetic defect (F), or a carrier of a genetic defect (C) will appear on pedigree certificates and on the Society’s website.

The abbreviations are as follows: -


Congenital Muscular Dystonia 1 CM1
Congenital Muscular Dystonia 2 CM2
Crooked Tail Syndrome CTS
Dwarfism DW
Gingival Hamartoma and Osteopetrosis HAM
Prolonged Gestation PG
Arthrogryposis and Cleft Palate AP
Protruding Tongue PT
Not tested Abbreviation will not appear on cert.
Free of the defect F
A Carrier of the defect C

The above abbreviations will appear on the front of pedigree certificates, with the legend on the reverse.

Disease Summary

1- CMDI: Congenital muscular dystonia I

- Lethal within days around birth

- Default in muscular relaxation

- Mutation identified, direct test proposed

2- CMD2: Congenital muscular dystonia II

- Lethal within hours around birth

- Default in neuro-muscular relaxation

- Mutation identified, direct test proposed

3- CTS: Crooked Tail Syndrome

- Not lethal per se but > 25% euthanized on welfare grounds

- Growth retardation, stocky head, extreme muscular development, scoliosis, spastic paresia: economic losses

- Two mutations identified in the same gene: combined direct test proposed to detect both mutations

4- DW: Severe growth retardation (dwarfism) and decreased resistance to infections

- Not lethal per se but 40% died before 1 year from recurrent infections

- The remaining 60% are severely growth retarded and culled for health related reasons: economic losses

- Mutation identified, direct test proposed

5- HAM: Gingival hamartoma and osteopetrosis

- Lethal around birth, some can survive a few weeks

- Complications during parturition, cows often culled

- Vascular mass (1 to 15 cm) in the mouth, abnormal skull shape

- Blindness

- No bone marrow cavity in the long bones (osteopetrosis)

- Mutation identified, direct test proposed

6- PG: Prolonged Gestation

- Parturition fails to occur, upon medical induction, calves are born alive but die within hours

- Gestation can last up to 14 months

- Mutation localised, indirect test proposed

7- AP: Arthrogryposis and cleft Palate

- Lethal before birth

- Arthrogrypose, cleft palate, blindness, umbilical hernia

- Complications during parturition, cows often culled

- Mutation localised, indirect test proposed


Protruding Tongue

Research is still being undertaken on this condition and, as yet, it is not confirmed as a defect caused by genetics, there may be other health issues that lead to these symptoms. For Belgian animal data on this condition click here


An actual defective calf will only occur where both the sire and the dam are carriers (C) of a disease. Where only one parent is a carrier no defective calf will appear; however the condition can be carried forward in future generations.

When selecting bulls, it is important that you are aware of the carrier status of the females in your herd.

These can easily be tested by sending a blood sample to Liége University, Belgium.

Sample Submission Form

GIGA - Genetic defects in Belgian Blue Cattle

Conditions for Import Authorisation

Shipping Samples from UK to Belgium