Fluctuations in somatic cell count and their impact on individual goat milk quality throughout lactation

Somatic cell count is used by the dairy industry as an indicator of milk quality and udder health. However, in goats, its reliability is significantly masked by noninfectious variables such as the milk secretion process and physiological lactation changes. Additionally, notable individual variability between goats might exist. This study aimed to investigate fluctuations in SCC in individual goats during an entire lactation and to examine the relationship between SCC and milk parameters such as bacterial count and chemical composition. Individual milk samples from 40 Norwegian dairy goats from the university herd were collected monthly across an entire lactation including the pasture period. The goats were categorized based on SCC levels to analyze patterns in chemical components within these groups. Notably, goats exhibited increased SCC and decreased bacterial counts when moved to summer grazing pastures. At that stage, milk samples from goats with the highest SCC (>2,000 × 10³ cells/mL) showed a distinct decrease in individual bacterial counts. The SCC level affected several milk components (especially lactose, protein, and various minerals), as well as pH. These effects were further amplified when considering the interaction with the lactation stage, influencing a broader range of variables. The results presented in this study provide new insights into the effect of SCC on milk composition and its critical role. These insights underscore the necessity for establishing lactation-specific thresholds for interpretation, as well as for making adjustments in quality payments.