Monitoring udder health in dairy cows is most effectively done by measuring the somatic cell count in milk. Somatic cells are mainly white blood cells and some shed epithelial cells. In a healthy udder, their number is low, but when mastitis or udder infection occurs, the immune system sends more cells into the milk, causing the count to rise. This makes somatic cell count a direct and sensitive indicator of udder inflammation, capable of detecting even subclinical infections that don’t show obvious symptoms. In practice, this measurement can be taken for individual cows or assessed in bulk milk from the herd. Keeping effective SCC levels helps manage mastitis risk and milk quality. The other options—milk calcium level, blood urea nitrogen, and blood potassium—do not specifically reflect udder infection or inflammation and are used for broader metabolic or nutritional status rather than focusing on udder health.