Bulldog Dwarfism (Chondrodysplasia) in Dexters

Quick Summary

Bulldog dwarfism is a lethal genetic defect of Dexter cattle. Affected fetuses have severe disproportionate dwarfism, a short vertebral column, a large head, and are naturally aborted around seven months of gestation. The two known mutations are specific to Dexter cattle and may be present in Dexter crossbreds.

Phenotype: Affected fetuses have severe disproportionate dwarfism, a short vertebral column, a large head, and are naturally aborted around the seventh month of gestation.

Mode of Inheritance: Incomplete dominance

Alleles: N = Normal/Unaffected, BD1 = Bulldog Dwarfism BD1 mutation, BD2 = Bulldog Dwarfism BD2 mutation

Breeds appropriate for testing: Dexter, Dexter crosses, Miniature Jersey, Miniature Zebu

Explanation of Results:

  • Cattle with N/N genotype will not have these types of bulldog dwarfism and cannot transmit either of these bulldog dwarfism variants to their offspring.
  • Cattle with N/BD1 or N/BD2 genotype will not be affected by these types of bulldog dwarfism, but are carriers. They will transmit the bulldog dwarfism variant they carry to 50% of their offspring. Matings between two carriers result in a 25% chance of producing a calf with bulldog dwarfism.
  • Cattle with BD1/BD1, BD2/BD2, or BD1/BD2 genotype will have bulldog dwarfism. Fetuses with any of these genotypes are expected to be naturally aborted around the seventh month of gestation.
Price

$25 one test per animal for Dexter BD1 Bulldog Dwarfism
$75 one test per animal for Dexter BD2 Bulldog Dwarfism (flat fee - not available as part of discount package)

Also available as part of the following packages:

$35 Dexter BD1 Bulldog Dwarfism + one test from list below
$45 Dexter BD1 Bulldog Dwarfism + two tests from list below
$55 Dexter BD1 Bulldog Dwarfism + all tests from list below

Additional Details

Inheritance of a form of chondrodysplasia known as bulldog dwarfism has been documented in Dexter cattle since the early 1900s. Among other defects, affected fetuses have severe disproportionate dwarfism, a short vertebral column, and a large head, and are naturally aborted around the seventh month of gestation. The defect is a major problem for Dexter breeders, as one copy of the defective allele produces the short-legged phenotype of Dexter cattle. Thus, selection for this phenotype maintains a lethal allele in high frequency in the population. Breeding carrier animals together will produce 25% affected fetuses.

Research by investigators in Australia determined that the bulldog dwarfism in Dexters is caused by two mutations in the aggrecan gene (ACAN). The most common mutation is BD1 (2266_2267ins-GGCA). A second mutation in the same gene – BD2 (–198C>T) – accounts for bulldog dwarfism in one particular bull lineage. Diagnostic testing for BD1 and BD2 helps Dexter breeders avoid production of bulldog calves.

 

Note: Each of the two mutations (BD1 & BD2) is detected by a separate test, and each test must be purchased individually on MyVGL.
Turnaround Time
2-6 business days
Type of Sample

Species

Type of Test

Results Reported As

 

Bulldog Dwarfism BD1
Test Result Bulldog Dwarfism BD1
N/N Normal. Does not have the Dexter BD1 Bulldog mutation.
N/BD1 Carrier. Has one copy of the Dexter BD1 Bulldog mutation. Breeding to another carrier will produce 25% affected calves.
BD1/BD1 Affected fetus. Has 2 copies of the Dexter BD1 Bulldog mutation.

 

Bulldog Dwarfism BD2
Test Result Bulldog Dwarfism BD2
N/N Normal. Does not have the Dexter BD2 Bulldog mutation.
N/BD2 Carrier. Has one copy of the Dexter BD2 Bulldog mutation. Breeding to another carrier will produce 25% affected calves.
BD2/BD2 Affected fetus. Has 2 copies of the Dexter BD2 Bulldog mutation.

 

Compound Heterozygote (only found in affected fetuses)
Test Result Bulldog Dwarfism BD1
BD1/BD2 Affected fetus. Has 1 copy each of Dexter BD1 and BD2 Bulldog mutations.
References

Harper, P.A., Latter, M.R., Nicholas, F.W., Cook, R.W., & Gill, P.A. (1998). Chondrodysplasia in Australian Dexter cattle. Australian Veterinary Journal, 76, 199-202. doi: 10.1111/j.1751-0813.1998.tb10129.x

Cavanagh, J.A., Tammen, I., Windsor, P.A., Bateman, J.F., Savarirayan, R., Nicholas, F.W., & Raadsma, H.W. (2007). Bulldog dwarfism in Dexter cattle is caused by mutations in ACAN. Mammalian Genome, 18, 808-814. doi: 10.1007/s00335-007-9066-9