Genetic analysis of milk urea concentration and its genetic relationship with selected traits of interest in dairy cows

The aim of this study was to estimate genetic parameters milk urea concentration (MU) and its correlations with production traits, longevity, functional traits in the first 3 parities dairy cows. edited data set consisted 9,107,349 MU test-day records from 560,739 cows 2,356 herds collected during years 1994 2020. To MU, 109 randomly selected herds, a total 770,016 records, were used. Genetic estimated breeding values using multiple-trait (parity) random regression model. Herd-test-day, age-year-season calving, days classes (every 5 d as class) used fixed effects, whereas effects herd-year permanent environment, animal modeled regressions Legendre polynomials order 2. average daily heritability repeatability 365 0.19, 0.22, 0.20, 0.48, 0.47, respectively. mean correlation among ranged 0.96 0.97. for bulls (n = 1,900) ?9.09 7.37 mg/dL. In last 10 yr, trend has gradually increased. between 11 interest –0.28 (milk yield) 0.28 (somatic cell score). findings can be step development routine evaluation inclusion into selection program Walloon Region Belgium.