Evaluation of variability of dairy characteristics of cows depending on the duration of lactation activity

The scientific article presents the results of studying the indicators of variability of signs of dairy productivity depending on the duration of lactation in Holstein cows. Analysis of the data showed that modern dairy cattle have high productivity indicators. The age structure of the herd shows that some of the animals are used for a sufficiently long time, that is, there are cows in the herd with a high duration of productive use and good indicators of resilience. As a result of research, it was found that they all had high milk yield, which depend on the age characteristics of lactation activity. The difference between the minimum and maximum indicators of milk yield ranged from 5956 (5th lactation) to 8284 kg (4th lactation), according to MJ - from 0.48 (7 lactation) to 1.47% (1 lactation) and MJ from 0.31 (7 lactation) to 0.51% (1 lactation). The coefficients of variation (Cv) for milk yield, MJ and MDB in milk confirm that the variation was in a normal ratio. Analysis of the variability of milk traits will allow further effective selection work to improve them.