In this thesis we were studying the effect on the course of the lactation curve in dairy cows. Not only calving season but also day length, nutrition, health status, age at first calving, milking frequency and breed have a significant influence on the lactation curve. We have also included in this thesis a review of data obtained from the Central Cattle Database for the period 2010-2022 for Brown Swiss, Simmental and Holstein dairy cows included in the milk recording. Milk persistency was expressed by persistency index P2:1 and P3:1 and reported for primiparous and multiparous cows of different breeds by months of calving. Lactations starting in autumn and winter have usually the best milk persistency. Cows calving in autumn (September, October) had the best milk persistency, while cows calving in spring had the worst. Holstein cows had better milk persistency than Brown Swiss and Simmental cows and heifers. In all three breeds, primiparous cows had better milk persistency compared to multiparous cows.
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