Further support for subclinical mastitis was provided by the significant (although modest) higher rectal temperature between 12 and 44 h after IMI compared to control groups, by the decrease in milk yield, by the increase in expression of CCL2 in MEC, and by a significant decrease in % PMN in blood within 24 h after IMI, likely caused by a temporary massive migration of neutrophils into the mammary gland. Here, CCL2 is linked to mastitis.