Retrospective: duration and efficiency of dairy cows productive lifespan depending on age at first calving and first lactation milk productivity

The retrospective analysis involved 562 Holstein cows, 545 Ukrainian Black-and-White dairy cows and 100 Ukrainian Red-and-White dairy cows in Breeding Station Terezyne, Kyiv region. The influence of age at first calving and first lactation milk yield on the duration and efficiency of the productive lifespan of cows was studied. The results showed that with the increase of age at first calving from less than 22 to more than 34 months there was a steady tendency to reduction in the longevity and lifetime productivity of cows. There was found a statistically significant (P