Mastitis — inflammation of the mammary gland — is the most costly and welfare-significant disease of dairy cattle. Dry cow therapy (DCT) — antibiotic treatment at drying-off to prevent or cure mastitis during the non-lactating period — is a cornerstone of mastitis management with important welfare and antimicrobial stewardship dimensions.
Mastitis and Animal Welfare
Clinical mastitis causes significant pain, fever, and systemic illness. Affected cows show behavioral indicators of pain including reduced feed intake, altered posture, and decreased social interaction. Severe clinical mastitis causes acute systemic illness that can be life-threatening without treatment. Subclinical mastitis — infection without obvious clinical signs — causes chronic immune activation and reduced milk quality without the acute welfare crisis of clinical disease, but may progress to clinical mastitis if untreated.
Selective vs. Blanket Dry Cow Therapy
Traditional blanket DCT — treating all cows at drying-off regardless of infection status — provides comprehensive mastitis prevention but uses antibiotics prophylactically in cows without confirmed infection. Selective DCT — treating only cows with evidence of intramammary infection at drying-off — reduces prophylactic antibiotic use in alignment with antimicrobial stewardship principles.
The welfare implications of selective DCT require careful consideration. Cows with subclinical infection not identified and treated at drying-off may develop clinical mastitis in the next lactation, causing welfare costs that blanket treatment would have prevented. Accurate identification of infected cows through somatic cell count records, California Mastitis Test, and bacteriological culture is essential for welfare-safe selective DCT implementation.
Internal Teat Sealants
Non-antibiotic internal teat sealants — bismuth subnitrate preparations that create a physical barrier in the teat canal — provide mastitis protection during the dry period without antibiotic use. Used alone in uninfected cows, or alongside antibiotic DCT in infected cows, sealants reduce new infection rates and support welfare by preventing mastitis without contributing to antimicrobial resistance. Correct administration technique is essential — improper infusion introduces bacteria, potentially causing iatrogenic mastitis.
Monitoring and Early Treatment
Early detection and prompt treatment of clinical mastitis in lactating cows is the highest-return welfare intervention for mastitis management. Twice-daily observation of fresh cows — those most vulnerable to mastitis — combined with daily milk quality assessment (strip cup, inline sensors) enables treatment initiation before disease becomes severe. Welfare outcomes are substantially better for mastitis cases treated within hours of clinical sign onset than those where treatment is delayed.