(Holstein/Friesian calves)

This defect was disseminated throughout the international Holstein herd from a founder bull in the USA whose descendants have been used extensively in the international Holstein herd. The disease is characterised by progressive leucocytosis emanating from a deficiency of an adhesion factor on the surface of leucocytes that is essential for leucocytes to migrate from blood vessels to sites of infection. Consequently, affected calves suffer with repeated bacterial infections.

AI centres select against BLAD heterozygotes when screening bulls for entry to their centres.

Specimens required

See Collection of hair samples for DNA testing

For diagnosis of the disease and for heterozygote detection:

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