Variability and correlation of milk urea content with parameters of cow productivity

During the work, 24774 individual milk samples for Ayrshire cows (Karelia, Russia) with an annual yield of over 8.300 kg were tested (1.355 cows) every month last three years. The urea content averaged 32.19 mg% a daily 25.5 kg. In at age first two lactations, was higher than adult animals. in increased from 31.46 to 33.56% increasing yield. summer and early autumn, concentration lower spring winter. A reliable positive correlation obtained yield, lactose, negative – protein, dry matter, non-fat residue, number somatic cells, lack connection fat freezing temperature milk. bull's genotype has significant effect on amount urea. Heritability coefficient (h 2 ) range 0.222 - 0.367.