We evaluated the variability of daily milk yield (DMY) of cows and estimated its correlations with production, functional and health traits. The dataset included 278,531 DMY records collected on 3 farms between 2004–2020 in 2002 Holstein cows. Cows were required to have records for at least 50 days of the first lactation. All records were used up to 305 days in milk (DIM). The first DIM must have been lower than 150.