Invited review: Herd-level udder health indices derived from repeated individual somatic cell count measurements

Abstract

Subclinical mastitis remains a major challenge in dairy production, affecting animal health and welfare, milk quality, profitability, and antimicrobial use. This narrative review synthesizes current knowledge on herd-level udder health monitoring, focusing on indices derived from repeated individual cow SCC measurements. Using an epidemiological framework based on the dairy cow life cycle, it highlights how SCC data from routine milk recording can be used to monitor udder health across physiological stages, including periods surrounding the nonlactating phase. The review presents key herd-level udder health indices, discusses their interpretation, strengths, limitations, and reported reference values, and emphasizes the need for standardized definitions and thresholds. Its objective is to provide veterinarians and dairy producers with practical guidance for implementing robust mastitis monitoring strategies across diverse dairy production systems.