Cow 1419 had a concentration of 420 ng/ml of S100A12 in milk from the control udder at 16 h post-infection while the S100A12 levels in the udders that had been challenged with 1 × 105 and 1 × 106 bacteria were almost five times greater (1920 ng/ml in the milk from both udder quarters) (P < 0.01). The gene discussed is S100A12; the disease is infection.