Genetic Assocciation of Test-day Milk Urea Concentration with Milk Yield in Primiparous Holstein Fresian Cows

The aim of this study wos to estimate genetic parameters of milk urea concentration (MUC) and the relationships with milk yield (MY) in the first lactation of Holstein Friesian cows. Data consisted of 952 test day records of MY and MUC on 52 first lactation Holstein Friesian cows calving from 2015 and 2016 at Agricultural Research and Development Station (ARDS) Simnic-Craiova, Romania. Random regression models were used to estimate genetic parameters and associations between traits. The coefficient of varation for MUC in the first parity was 38,34%. Average daily heritability of MUC was 0,20. In the first parity,genetic correlation between MUC and MY was positive and increased with days in milk from 0,18 to 0,38.This results confirm that MUC,used for management porposes,may slightly increase due to selection for milk production trait