The study of repeatability of milk yield of Brown Swiss, Sychevsky and Black-and-White cows of the method of correlation analysis and analysis of variance revealed overall for the three breeds, the relation between the milk yield during the productive life of the animal. The value of the coefficient of repeatability for milk yield for any of the lactations with maximum and average for the life that is comparable and exceeds the magnitude of the relationship between the yields of adjacent lactations. At lifetime variation of milk yield of cows, their level as a whole remains and is defined by milk yield for the first lactation. Research was carried out based on the data of in-farm pedigree records in the "SELEX-Dairy Livestock" breeding program of the breeding farms of the Smolensk Region for: the brown Schwitz livestock breeding reproducer of the SPK "Druzhba", the Sychevskoe stud farm of the PK KP "Rybkovskoe", the black-and-white of the collective farm of the stud farm "Radischevo". Milk yields at standard or finished shortened lactation periods were analyzed. Derived regularities form a basis for sufficiently precise forecasting of milk yields for adjacent lactation based on lactation of any type (shortened or standard), as well as the maximum and mean milk yield per life.