How did testing Holstein bulls for the BLAD gene help prevent hereditary disease in calves?

Bovine leukocyte adhesion deficiency (BLAD) is a hereditary disease in Holstein calves caused by the inheritance of two copies of a recessive gene. Because this gene was once present in nearly 25 percent of Holstein bulls, it posed a significant risk to the health of the cattle population, leading to severe infections and early death.1

Testing bulls for the BLAD gene has been instrumental in preventing the disease because it allows breeders to identify carriers—animals that possess one copy of the gene but remain healthy. By screening bulls before they are used for artificial insemination, producers can avoid breeding carriers together. This practice prevents the birth of calves that would inherit two copies of the recessive gene, thereby effectively managing the disease and avoiding a potentially major problem in the industry.1