Correlation of productive longevity and reproductive functions in dairy cows

The Ural type of the domestic Black-and-White mottled breed is characterized high milk-yield rates and good suitability for industrial milking technology. milk yield increase led to a deterioration reproductive functions in livestock. As result research it was found that process prolonged using cattle, cows regularly changes, reaching highest among mature by 3rd lactation, then gradually decreases, remaining sufficiently stable. decrease starts from 13 kg (in 4th lactation comparison with lactation) goes 663 (from 8th lactations). That makes on average 132.6 per period, or 1.7%. quality indicators changed better 1st 10th lactation. turned out be more variable; they had coefficient variability 20.7 17.6, which indicates quite wide possibility selection herd this trait. not related duration service period; modern Holsteinized cattle will provide negative impact cows.