Dwarfism in Cattle

Condrodysplasia

History

Found in all breeds of cattle. Dwarfism was very prevalent in the 1940's-60's but was not diagnosed in all breeds until 2000. It was considered one of the biggest genetic defects in the Black Angus Industry.

What is the Disease?

Dwarfism in cattle is a defect found in various cattle breeds that results in the calf being born abnormally small. It has several variations of severity, the worst being Bulldog or Complete Dwarf.

Bulldog Dwarf: Calf will die at birth or soon after. The calves with bulldog dwarfism have an extremely compressed body.

Snorter Dwarf: Calves have a short-blocky appearance and have a deformed nose that caused labored breathing

Long-Headed Dwarf: Causes a small size due to affecting the growth plates, mainly in the legs. The bones in the calf's head grown normal while the leg bones do not develop as they should so their head seems in-proportionate to the rest of the body.

Genetic Transmission

Dwarfism is considered an autosomal recessive. While the specific gene varies from breed to breed of cows, Angus cattle show a mutation in the PRKG2 (D2) gene.


A Heterozygous cow bred to a heterozygous bull will result in

1/4 homozygous normal calf

1/4 homozygous D2 calf (some form of dwarfism)

1/2 heterozygous normal calf but carrier for dwarfism

Phenotypes

Other Causes of Disease

Dwarfism can also be caused by the cow being exposed to toxins during her pregnancy. If a cow gets an infection, has a poor body condition score or is subject to extreme weather conditions, dwarfism can appear in the calf when born.

Diagnosis

A veterinarian can perform a necropsy on the calf and complete lab work in order to determine if the dwarfism was truly caused by a genetic mutation or from environmental factors.

Prevention

To prevent dwarfism in cattle, must ensure all cows and bulls do not carry the PRKG2 mutation. A simple genetic test can check for the presence of the gene. The Angus Association will not register any cattle that are carriers of the gene mutation even if they do not show symptoms.

Discussion Point

While dwarfism is more notably caused by a genetic mutation, it is interesting to find that it can also be caused by various environmental factors that a cow faces during gestation. Dwarfism is not the only disease that can be caused by genetic mutation or environmental factors. I am curious as to what actually determines the severity of dwarfism in each calf born with the mutation. While a calf that ends up homozygous recessive and displays the dwarfism characteristics, their phenotype varies from one calf to the other.