Interrelations Betw Een The Milk Urea Concentration And Production And Reproduction Performance Of Dairy Cow S

The objective of the study was to investigate the correlation between the milk urea (MU), milk yield and reproductive performance using milk recording tests and the health check results. Weak to average negative correlation was found between MU and the milk yield (r = -0.44 and r = -0.34; p>0.05), milk protein (r = -0.22; p<0.05) and milk freezing point (r = -0.33; p<0.01). Higher milk fat was found in cow milk with MU below 30 mg dL(-1) in comparison with cow milk which had MU above 30 mg dL(-1), 4.0 +/- 0.77% and 3.9 +/- 0.75%, respectively. High MU fluctuations within a cow group can be observed if cows of different productivity levels are grouped together or if there are too many animals in one group. Correlations between MU and times of artificial insemination or the service period were not established, possibly due to successful veterinary measures. In conclusion we emphasize the necessity on large dairy farms to analyse MU concentration in relation to milk protein and fat concentration for individual animals and in each feeding group separately. The study was the part of the State Research Project (AgroBioRes) No. 2014.10-4/VPP-7/5; subproject VP29.