The objectives of this study were to determine the eff ects of environmental and physiological factors on milk urea content (MU) and milk production traits and to estimate heritability and repeatability for MU and milk production traits. Milk yield and MU, fat, protein, lactose, somatic cell count (SCS) and freezing point (FP) of milk were collected from the herd control data from August 2008 to August 2009 from dairy herd of the Study and research farm “Vecauce” of the Latvia University of Agriculture. Milk content parameters for total 794 milk samples were analyzed in accredited milk quality laboratory. The investigation data was processed using a program SPSS. Genetic parameters of MU and milk production traits were estimated by REML method using WOMBAT soft ware applying a repeatability animal model. The average MU was 16.55 mg dL-1 and milk yield was 20.37 kg per test day. The average fat, protein and lactose contents were 4.60, 3.56 and 4.70%, respectively. The average SCS and FP of milk were 2.40 and minus 0.529oC. Milk productivity traits varied depending on season, lactation number and stage of lactation (p

dairy cattle; genetic parameter; milk yield; urea

Published by University of Zagreb, Faculty of Agriculture, Zagreb, CROATIA
Sponsored by Ministry Science and Education of the Republic of Croatia