Streptococcus dysgalactiae isolates at calving and lactation performance within the same lactation

Area of Science:

• Veterinary Medicine
• Dairy Science
• Bacteriology

Background:

• Streptococcus dysgalactiae is a significant mastitis pathogen in dairy cattle.
• Understanding its impact on milk production and cow health is crucial for effective herd management.

Purpose of the Study:

• To investigate the association between early lactation Streptococcus dysgalactiae isolates and key production and health parameters.
• To evaluate the impact on milk yield, somatic cell count (SCC), clinical mastitis, and culling within the same lactation.

Main Methods:

• A study involving 178 commercial dairy herds with various dry-cow treatments and teat disinfection protocols.
• Cows were sampled in early lactation; Strep. dysgalactiae-positive and negative cows were monitored throughout lactation.
• Mixed models and survival analyses were used to assess milk yield, SCC, clinical mastitis, and culling risks.

Main Results:

• Streptococcus dysgalactiae-positive cows exhibited significantly higher SCC throughout lactation.
• These cows produced less milk (334 kg for primiparous, 246 kg for multiparous) over a 305-day lactation.
• The hazard ratio for clinical mastitis was 2.3 and for culling was 1.6 in Strep. dysgalactiae-positive cows.

Conclusions:

• Early lactation Streptococcus dysgalactiae infection negatively impacts dairy cow health and productivity.
• Management strategies targeting Strep. dysgalactiae are essential to mitigate economic losses and improve animal welfare.
• Co-infection with Staphylococcus aureus further increases culling risk.