Causes

Mastitis, or inflammation of the mammary gland, is generally classified into two categories:

• Environmental bacteria such as Escherichia coli, Klebsiella spp, environmental streptococci and environmental staphylococci
• Contagious bacteria including Streptococcus agalactiae, Staphylococcus aureus and Mycoplasma spp., which are transmitted from cow to cow

Signs

Clinical mastitis:

• Signs will vary with severity; may be localized, or in rare cases, systemic
• Udder may appear hot, swollen, red or painful
• Milk may contain flakes, clots or blood
• Milk production may decrease
• Systemic signs may include fever, depression, appetite loss

 Subclinical mastitis:

• Cows may show no clinical signs
• Milk can appear normal
• Affected cows will have elevated somatic cell counts

Diagnosis

• Based on clinical signs, abnormal milk
• Bacterial culture +/– sensitivity
• Somatic cell count (especially for subclinical mastitis) >200,000 cells per mL

Treatment

• Work with your veterinarian to develop a milk quality program that includes targeted mastitis treatment protocols
• Ideally, use of bacterial culture to guide antibiotic treatment choices can help reduce overall antibiotic use, milk discard and hospital pen time
• Antibiotic treatment is generally beneficial for Gram-positive bacteria; treatment of mild or moderate mastitis caused by E. coli  is generally unnecessary
• Lactating cow therapy: Antibiotic choice, as well as route and duration of administration, will depend on organisms involved:
  • For mild to moderate infections, use the appropriate intramammary mastitis tube
  • For severe infections, systemic antibiotics may be appropriate, as well as supportive therapy
• Dry cow therapy: Treatment immediately after the last milking of lactation can help eliminate existing infections and prevent new infections during the dry period:
  • lntramammary antibiotics, using blanket cow therapy (in all quarters of all cows), are generally most effective at treating and preventing new infections
  • Selective dry cow therapy may be appropriate for some herds
  • A teat sealant, used alone (only in uninfected udders) or with intramammary antibiotics, can help supplement teat defenses

Prevention

• Keep cow environment clean and dry
• Make sure milking equipment functions properly
• Sanitize and dry teats before milking 
• Wear gloves during milking and disinfect hands between cows
• Apply a germicidal teat dip after milking
• Establish an effective dry cow therapy program
• Vaccinate cows against coliform mastitis
• Cull cows with chronic mastitis