It is present in milk in its native, active state and its concentration is known to increase during mastitis.7,46 HRG was also identified as an early elevated APP and is a major plasma protein in a range of mammals, including cattle.47,48 It plays a role in blood coagulation, fibrinolysis, and innate immune systems and is also thought to have antibacterial properties.48 As HRG was upregulated as early as 36 h PC and was returned to normal levels towards the end of the experiment, it may have a role as a diagnostic marker in detecting the occurrence and resolution of IMI. This evidence concerns the gene APP and mastitis.