Genetic Parameters for Milk urea in swiss dairy cattle breeds

The objective of this study was to estimate repeatability scores and variance components (VC) for milk urea in the Swiss cattle breeds Braunvieh (BV), Original Braunvieh (OB), Holstein (HO), Montbéliard (MO), Red Holstein (RH), Swiss Fleckvieh (SF) and Simmental (SI). For this purpose, milk urea results from 2,315,437 standard lactations yields (BV=955,231; OB=80,016; HO=265,775; MO=44,590; RH=474,289; SF=367,720; SI=127,816) with totally 2,335,267 pedigree records (BS=676,368; OB=73,927; HO=416,634; MO=70,635; RH=526,760; SF=431,080; SI=139,863) were used. The data were collected in the years 2010-2019. Genetic variances and covariances were estimated by REML using the software ASReml 4.2. The model to estimate VC and repeatabilities included the fixed effects number of lactation and milk yield, the random effects farm and sire, as well as a random additive genetic component and a permanent environmental effect. Estimated heritabilities and standard errors were 0.37±0.004, 0.52±0.012, 0.32±0.007, 0.20±0.013, 0.27±0.005, 0.34±0.006, 0.38±0.009 in BV, OB, HO, MO, RH, SF and SI breed, respectively. The repeatability coefficients varied between 0.30±0.008, 0.34±0.003, 0.40±0.003, 0.40±0.003, 0.44±0.006, 0.45±0.002 and 0.56±0.006 in MO, RH, SF, HO, SI, BV and OB, respectively (±standard error). The results are consistent with other studies and show that genetic modification of milk urea by selection is possible.