UC Davis School of Veterinary Medicine Veterinary Genetics Laboratory
Bulldog Dwarfism (Chondrodysplasia) in Miniature Zebu
Introduction

Inheritance of a form of generalized chondrodysplasia known as bulldog dwarfism has been documented in several breeds of cattle including Miniature Zebu. Among other defects, affected fetuses have severe disproportionate dwarfism, short, compressed vertebral column, a large head and short, stocky limbs. Fetuses with this genetic defect are naturally aborted around the seventh month of gestation. 


A mutation in the cartilage development gene Aggrecan (ACAN) was identified as the cause of bulldog dwarfism in Miniature Zebu cattle. The mutation is one base pair insertion (ACAN:c.5686insC) in the sequence of exon 12 of the gene which results in production of truncated protein and loss of its critical function needed for normal bone and cartilage development. This mutation (named here BDz for simplicity) has an autosomal recessive lethal mode of inheritance. This means that both males and females are equally affected and that affected fetuses are not viable and are aborted later in pregnancy. Two other mutations (BD1 and BD2) in the same gene are responsible for bulldog dwarfism in Dexter cattle.

The VGL offers a test for bulldog dwarfism in Miniature Zebu. Test results help breeders determine if carriers are present among breeding stock and to use mating strategies to avoid producing affected calves. Breeding carrier animals together is not advised because this type of mating has a 25% chance of producing affected calves. The test can also be used by veterinarians to confirm bulldog dwarfism diagnosis of aborted fetuses.

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Allow 2-6 business days for results.

Results reported as:

N/N

Normal – no copies of the BDz mutation are present.

N/BDz

Carrier – 1 copy of the BDz mutation is present. Animal is normal but can produce affected offspring if bred to another carrier.

BDz/BDz

Affected – 2 copies of the BDz mutation.

 

Reference:

Struck A-K, Dierks C, Braun M, Hellige M, Wagner A, Oelmaier B, Beineke A, Metzger J and Distl O. (2018) A recessive lethal chondrodysplasia in a miniature zebu family results from an insertion affecting the chondroitin sulfate domain of aggrecan. BMC Genetics 19:91, https://doi.org/10.1186/s12863-018-0678-8.


Cavanagh  JAL, Tammen I, Windsor PA,  Bateman JF, Savarirayan R, Nicholas FW  and  Raadsma HW. (2007) Bulldog dwarfism in Dexter cattle is caused by mutations in ACAN. Mammalian Genome 18:808-814.

 
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