Clinical mastitis in two California dairy herds participating in contagious mastitis control programs

Area of Science:

• Veterinary Medicine
• Dairy Science
• Animal Health

Background:

• Clinical mastitis is a persistent challenge in dairy herds.
• Established mastitis control programs targeting Streptococcus agalactiae and Staphylococcus aureus were in place.
• Herds maintained good hygiene, husbandry, and low somatic cell counts (SCC).

Purpose of the Study:

• To describe the occurrence and etiological agents of clinical mastitis in two large California dairy herds over three years.
• To identify risk factors associated with clinical mastitis incidence.

Main Methods:

• Retrospective analysis of clinical mastitis cases over a 3-year period.
• Identification of etiological agents, focusing on coliform bacteria and environmental streptococci.
• Analysis of incidence based on lactation stage and season.

Main Results:

• An annual clinical mastitis incidence of 49% was observed in both herds.
• Coliform bacteria and environmental streptococci accounted for 60% of cases.
• Clinical mastitis was more prevalent in the early months of lactation, peaking in lactations 4 and 5.
• Incidence was highest during the rainy season (late fall and winter).

Conclusions:

• Coliform bacteria and environmental streptococci are significant etiological agents of clinical mastitis, even in herds with established control programs.
• Lactation stage and season are important factors influencing clinical mastitis occurrence.
• Further research into managing environmental pathogens and understanding lactation-specific susceptibility is warranted.