PROS1 and mastitis: In bovine pathology today, one of the most important APPs frequently used in clinical diagnostics is the hemoglobin scavenger protein, haptoglobin (Hp).2, 4 Haptoglobin has been shown to have diagnostic value in detecting subclinical (and clinical) mastitis using milk samples5 and has recently proven useful in distinguishing between different mastitis‐causing pathogens.6