Clinical bovine mastitis in Norway

Area of Science:

• Veterinary Epidemiology
• Animal Health Management
• Dairy Science

Background:

• Clinical mastitis (CM) is a significant concern in dairy cattle production.
• Understanding CM incidence is crucial for effective herd management and economic viability.
• The Norwegian Health Card System for Cattle (NHCSC) provides valuable data for epidemiological studies.

Purpose of the Study:

• To determine the incidence of clinical mastitis (CM) in Norwegian dairy cows.
• To estimate various risk measures associated with CM using national health data.
• To explore factors influencing CM incidence, such as herd size and geographical location.

Main Methods:

• Utilized data from the Norwegian Health Card System for Cattle (NHCSC) spanning 1992-1995.
• Calculated incidence density (ID), accounting for repeated CM episodes within the same cow.
• Employed actuarial and density methods to estimate annual and lactational risks for fixed cohorts.

Main Results:

• Overall incidence density (ID) for CM was 49 episodes per 100 cow-years at risk.
• Twenty-six percent of affected cows experienced at least two CM episodes annually.
• Incidence density for acute CM (ACM) was 30 episodes per 100 cow-years.
• Annual CM risk ranged from 0.32 to 0.35; lactational risk ranged from 0.32 to 0.34.
• CM incidence density tended to decrease with increasing herd size (in herds >5 cow-years).
• Significant geographical variation in CM incidence was observed, with higher rates in coastal areas.

Conclusions:

• The study provides a comprehensive overview of clinical mastitis incidence in Norwegian dairy cows.
• Factors such as herd size and geographic location are associated with CM risk.
• Findings highlight the importance of the NHCSC for monitoring and managing cattle diseases.