Genetic parameters for pathogen-specific mastitis resistance in Danish Holstein Cattle

Area of Science:

• Animal Genetics
• Dairy Science
• Veterinary Epidemiology

Background:

• Mastitis remains a significant concern in dairy herds, impacting animal welfare and economic profitability.
• Understanding the genetic basis of resistance to specific mastitis pathogens is crucial for effective breeding strategies.
• Previous research often focused on unspecific mastitis, potentially overlooking pathogen-specific genetic variations.

Purpose of the Study:

• To estimate heritabilities and genetic correlations for various pathogen-specific mastitis traits in Danish Holstein cows.
• To investigate genetic parameters for mastitis caused by Streptococcus dysgalactiae, Escherichia coli, coagulase-negative staphylococci (CNS), Staphylococcus aureus, and Streptococcus uberis.
• To analyze genetic correlations among pathogen groups (Gram-negative vs. Gram-positive, contagious vs. environmental).

Main Methods:

• Utilized data from 168,158 Danish Holstein cows calving between 1998 and 2006.
• Employed uni- and bivariate threshold models with Gibbs sampling for variance and covariance estimation.
• Calculated posterior means for heritabilities and genetic correlations of pathogen-specific mastitis traits.

Main Results:

• Heritabilities for pathogen-specific mastitis were lower (0.035–0.076) than for unspecific mastitis.
• Heritabilities for pathogen groups ranged from 0.053 to 0.087.
• Genetic correlations among pathogen-specific traits varied (0.45–0.77), influenced by pathogen-specific immune responses.

Conclusions:

• Pathogen-specific mastitis traits should be treated as distinct entities in genetic evaluations.
• Genetic evaluation for pathogen-specific mastitis resistance is beneficial due to direct infection measurement and differing economic impacts.
• Improved recording of pathogen information is critical for accurate genetic evaluation of udder health.