(Poll Herefords)

Stimulus-responsive myoclonic spasms in bright and alert calves is the striking clinical feature of this disease. The majority of affected calves have hip lesions, most frequent being fractures of the acetabulum, and less commonly, fractures of the head of the femur. No consistent histological findings.

Diagnosis

History, clinical signs; confirmed by DNA analysis.

Specimens required

See Collection of hair samples for DNA testing

Diagnosis and heterozygote detection:

1. 20 to 25 hairs, with roots attached, from the distal end of the tail.