State-Level Geographic Disparities and Temporal Patterns in Milk Somatic Cell Counts Across the United States, 2011–2023

The dairy industry faces challenges from mastitis, which affects milk quality. Somatic Cell Counts (SCCs) are key indicators of udder health, subclinical mastitis presence, and legal thresholds. However, limited research has explored geographic disparities and temporal patterns in SCCs across the USA, despite their critical role in informing targeted herd management strategies, optimizing policy interventions, and ensuring consistent milk quality standards. This study aimed to examine temporal trends and geographic disparities in median weighted SCCs (mwSCCs) across USA states. This study analyzes SCC data using records from the Dairy Herd Improvement Association across 42–45 states between 2011 and 2023. State-level differences in mwSCCs were examined, with temporal changes assessed using percent differences between 2011 and 2023. Moran’s I and Local Indicators of Spatial Association (LISA) were used to identify spatial clusters of states with high and low mwSCCs. The mwSCCs decreased by 24.8%, from 234,000 cells/mL in 2011 to 176,000 cells/mL in 2023, with significant reductions in Virginia and Georgia, while Tennessee and South Carolina had minimal declines. However, Texas, California, and Colorado saw increases, with Colorado rising by 147.9%. Spatial clustering revealed high mwSCCs in the southeast and low levels in the northeast, highlighting the need for region-specific strategies.