Anotace:
The objective was to analyse (1) relationships between somatic cell score (SCS) i.e. logarithmic transformation of somatic cell count (SCC) and daily milk yield and milk components (fat, protein and lactose contents), and (2) factors aff ecting variation of these traits in Hostein cows. Test day records (10,892) from 2015 to 2020 were investigated. Relationships were characterized using linear correlations. Eff ects of fi xed factors: SCC class, parity, month in milk, sampling year and season, and random factors of cow and residual error were evaluated using mixed model. The factor SCC class was omitted in the analysis of SCS. There were found negative correlation coeffi cients between SCS and milk yield (-0.25) and lactose content (-0.36), and positive correlation coefficients between SCS and fat content (+0.12), and between SCS and protein content (+0.15). The considered fixed factors showed the significant influence on investigated traits. With increasing SCC, milk yield and lactose content decreased and fat and protein contents increased (this pattern agreed with pattern of correlation coeffi cients). Milk yield, fat and protein contents and SCS were lower in primiparas than in multiparas; lactose content showed the opposite pattern. The lowest milk yield and lactose content were found in autumn; the lowest fat and protein contents were found in summer. The highest SCS found in winter did not confi rm a hypothesis that higher temperatures and humidity have impact on cows’ susceptibility to infections and the number of pathogens to those cows are exposed. Further research is needed.