Mastitis — inflammation of the udder, almost always due to bacterial infection — is the most costly and one of the most welfare-significant diseases in dairy cattle globally. It causes pain, systemic illness, and premature culling, while representing the largest single use of antibiotics in dairy farming.
Mastitis ranges from subclinical (elevated somatic cell count, no visible signs — but associated with udder tissue damage and chronic discomfort) to clinical mild (abnormal milk only), moderate (abnormal milk plus visible udder signs), and severe/peracute (abnormal milk, swollen hot udder, systemic illness — fever, reduced appetite, depression). Severe mastitis causes acute intense pain and, with gram-negative infections (E. coli), endotoxaemia that can cause shock and death within hours. Welfare impact spans from chronic low-grade discomfort (subclinical) to acute life-threatening illness (peracute).
Mastitis pathogens are classified as contagious (spread cow-to-cow primarily at milking — Staphylococcus aureus, Streptococcus agalactiae) or environmental (contracted from the environment between milkings — E. coli, Streptococcus uberis, Klebsiella). Contagious mastitis control focuses on milking hygiene and teat condition. Environmental mastitis control focuses on housing hygiene, lying surface quality, and teat-end condition. Most herds have a mixture of both pathogen types.
All clinical mastitis causes pain. Treatment should always include: appropriate antibiotic therapy (administered by intramammary tube or systemically depending on severity and pathogen), NSAIDs for pain relief and anti-inflammatory effect (improving milk let-down and cow comfort), and supportive care for severe cases (IV fluids, oxytocin to aid milk let-down for natural drainage). Evidence strongly supports NSAID use in mastitis treatment — cows treated with NSAIDs show faster recovery, better milk production recovery, and improved welfare indicators.
Milking management is the primary driver of contagious mastitis transmission. Prevention measures include: pre-milking teat cleaning and drying (reducing teat-end contamination), post-milking teat disinfection (teat dipping or spraying with appropriate disinfectant — kills bacteria before they penetrate the teat canal), dry cow therapy (antibiotic treatment at drying off to clear existing infections and prevent new ones during the dry period), and culling of chronically infected cows (persistent reservoir for contagious pathogens).
Environmental mastitis control requires: clean, dry lying surfaces (deep-bedded sand or well-managed straw/mattress cubicles with daily fresh bedding), regular scraping of passages to reduce slurry accumulation, adequate teat-end callosity management (hard teat ends from over-milking impede teat canal closure), and ensuring cows can stand after milking while the teat canal closes (avoid pushing cows immediately into dirty housing post-milking).
Mastitis represents the single largest use of antibiotics in UK dairy farming. Responsible use includes: selective dry cow therapy (treating only cows with infected quarters or high SCC rather than blanket treatment — using internal teat sealants alone for low-risk cows), culture-guided treatment selection where feasible, and avoiding unnecessary treatment of subclinical infections in low-SCC cows. Reducing mastitis incidence through prevention directly reduces antibiotic use — a welfare and public health benefit.