Evaluation of the milk urea content in relation to milk production and composition in dairy cows

The aim of this study was to evaluate the milk urea content along with the dynamics of lactation and milk components in production dependency in Holstein dairy cows. Evaluation of daily milk yield in relation to milk urea presented a positive regression dependency, which was the strongest in early lactation (r = 0.860; P < 0.001), decreasing in mid lactation (r = 0.329; P < 0.001) and late lactation (r = 0.261; P < 0.001). Evaluation of milk protein in relation to milk urea showed a negative regression dependency, which was the strongest in early lactation (r= -0.850; P < 0.001), decreasing in mid lactation (r = -0.819; P < 0.001) and late lactation (r = -0.679; P < 0.001). The somatic cell counts in relation to milk urea confirmed a negative regression dependency in early lactation (r = -0.635; P < 0.05) and mid lactation (r = -0.818; P < 0.05), but no significance was found in late lactation. The results of the study confirm the influence of production factors (milk quantity and milk components) on the milk urea content. Dependencies found between the production, milk components and milk urea are applicable for the evaluation of protein nutrition and metabolic transformation of nutrients in dairy cows.