Summer Mastitis in Dry Cows: Prevention and Welfare

Key Facts

• Summer mastitis is caused by Trueperella pyogenes transmitted by Hydrotaea irritans flies
• Occurs during the dry period or in late-gestation heifers exposed to flies in summer
• Clinical signs include acute fever, painful quarter enlargement, foul secretion, and systemic toxemia
• The affected quarter rarely returns to function after clinical infection
• Fly control (pour-on insecticides, ear tags) and internal teat sealants are highly effective prevention

Welfare Considerations

Summer mastitis causes severe acute suffering through infection and toxemia. Affected animals show fever, depression, and obvious quarter pain. Without prompt treatment, pregnancy loss, permanent udder damage, and death can follow. The welfare imperative is early detection through daily checks of dry cows and heifers in fly-prone summer environments, combined with vigorous fly control. Internal teat sealants at drying off provide physical protection at modest cost and represent excellent welfare-cost investment.

What You Can Do

• Apply fly repellent ear tags and pour-on insecticides to dry cows and in-calf heifers in summer
• Apply internal teat sealant at drying off to prevent bacterial entry during the dry period
• Check dry cows and heifers daily during summer for udder swelling and fever
• Treat promptly with systemic and intramammary antibiotics plus NSAIDs when detected
• Move susceptible animals to less fly-prone shaded areas if practical during peak fly season