Bulldog dwarfism / Chondrodysplasia (ACAN, BD1/BD2) - Cattle

Bulldog dwarfism in cattle

This DNA test assesses two ACAN variants known as BD1 and BD2. The trait is also called Bulldog Calf Syndrome, congenital bovine chondrodysplasia, chondrodysplasia and bulldog calf. The analysis is relevant for Dexter and Scottish Highland cattle; both variants are assessed for both breeds.

ACAN encodes aggrecan, a protein with an important role in cartilage development and function. Carriers may show shorter legs or a chondrodysplastic type. Animals with two disease-associated ACAN alleles have the severe bulldog-calf presentation, often with late fetal loss or a stillborn, severely malformed calf.

What is tested?

• BD1: ACAN c.2266_2267insGGCA, a small insertion on chromosome 21.
• BD2: ACAN c.-198C>T, a rarer regulatory variant on chromosome 21.

Practical value of this test

The result shows whether the animal is clear, carries one of the tested variants, or has a risk combination for the tested ACAN variants. This helps breeders identify carriers correctly, avoid carrier-to-carrier matings and make targeted breeding decisions without unnecessarily excluding valuable lines.

For these ACAN variants the trait is described as autosomal incompletely dominant: one copy can give a milder chondrodysplastic effect, while two disease-associated copies lead to the severe bulldog-calf presentation.