Letter to the Editor: Associations between days open and dry period length versus milk production, replacement, and fertility in the subsequent lactation in Holstein dairy cows

The recently published retrospective observational study by Overton and Eicker (2025) is well conducted, revealing many associations between previous days open and days dry and their association with replacement risk and milk production in early subsequent lactation. However, the conclusions are unjustifiably bold considering that this is a retrospective observational study where the reason for the delay in days open is unknown and that controlled studies drawing different conclusions do exist.