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Canadian Bovine Mastitis Research Network

Our Research  I  Our Results 

What does CBMRN Research Show about the Mastitis Situation in 2009?

Clinical Mastitis
The Incidence of Clinical Mastitis
On a yearly basis, 31% of lactating cows in Canada experienced an episode of clinical mastitis. Among various herds, the incidence (rate of new udder infections) of clinical mastitis in lactating cows ranged from 3% to 110%. 

According to CBMRN findings, clinical mastitis cases among cows enrolled in the National Cohort of dairy farms were found to have the following symptoms:
  • 51% of cases – abnormal milk (flakes, clots, watery milk)
  • 38% of cases – swollen udder
  • 11% of cases – systemic signs (fever)

Incidence of Clinical Mastitis per Province
Provinces Incidence (% of cows)
Alberta 22
Quebec 28
Ontario & Atlantic 36
What Pathogens are Responsible for Clinical Mastitis?
At the national level, the most severe cases of mastitis are typically caused by:
  • Escherichia coli – 34.5%
  • Staphylococcus aureus – 12%
  • Coagulase negative staphylococci (CNS) – 11.5%
  • No significant growth – 7.6%
In Quebec, Ontario and the Atlantic provinces, clinical infections were more often caused by Staphylococcus aureus than by Escherichia coli.
Infections without Clinical Signs
Just before Drying-off
At least 17.7% of all quarters were infected. The proportion of infected quarters varied from 13.6% in Atlantic to 19% in Alberta. CNS was most often responsible for subclinical infections, followed by S. aureus. This was especially evident on Quebec dairy farms.
Two Weeks Post-calving
The situation improved slightly with a rate of 11.8% of infected quarters, ranging from 9.8% in Atlantic Provinces to 14.3% in Alberta. Again, the most common pathogens were CNS (4%), followed by S. aureus (3%).
During Lactation
The situation remained the same with a rate of 13.3% of infected quarters, ranging from 10.3% in Atlantic to 14.7% in Ontario. CNS was once again the most common pathogen in all regions (from 4.5% to 6.9%). During lactation, mastitis caused by S. aureus was fairly rare:
  • Alberta – 1.5%
  • Atlantic – 2.0%
  • Ontario – 2.7%
  • Quebec – 3.1%
 It is encouraging to note that no infection was diagnosed in 87% of all quarters sampled.

Member Access
Cohort data bank