Influence of different concentrations of milk urea nitrogen on the reproductive performance of Holstein cows.

The purpose of this study was to assess how various MUN levels affected the reproductive performance traits of Iranian Holsteins. The dataset used in this study included reproduction performance records for 16,000 Holstein cows and was gathered by the Animal Breeding Center and Promotion of Animal Products of Iran on 30 large dairy herds during 2018-2021. The MUN concentrations were grouped into four classes: [Formula: see text] mg/dL (MUN1), [Formula: see text] mg/dL (MUN2), [Formula: see text] mg/dL (MUN3), and [Formula: see text] mg/dL (MUN4).