Mastitis is the most costly and common disease of dairy cows worldwide, causing significant pain and suffering in millions of animals annually while driving overuse of antibiotics.
Mastitis causes genuine pain and suffering in affected cows. Clinical mastitis involves hot, swollen udder tissue that is sensitive to touch, along with systemic illness, fever, and reduced appetite. Cows with mastitis show altered gait, reduced social interaction, and avoidance of milking — behavioral indicators of pain. Subclinical mastitis, which causes chronic low-level inflammation, may affect even more animals without triggering treatment. High-producing dairy genetics that increase mastitis risk represent a fundamental welfare trade-off embedded in the structure of dairy production.