LATVIA UNIVERSITY OF AGRICULTURE - Latvijas ...

Diana Ruska, Daina JonkusMILK UREA CONTENT AS INDICATOR FEED PROTEINUTILIZATION AND ENVIRONMENTAL POLLUTION IN FARMSFigure 4. Milk urea content per control day in farms.Figure 5. Milk urea nitrogen content per control day in farms.Researchers from Europe (Bijgaart, 2003) confirmthat normal milk urea content in milk is from 15.0to 30.0 mg dL -1 . In our study, milk urea contentdiffered among the farms. Farm C were urea contentin milk significantly highest than recommended. Themeasurements of milk urea content could be used toassess the adequacy of protein feeding in dairy cowsand the efficiency of N utilization for milk production(Jonker et al., 1998; 2002; Nousiainen et al., 2004).The value of 20.8 mg 100 mL -1 milk urea content hasturned out to correspond to an optimal crude proteincontent of the ration, i.e., a ruminal N balance of zero.The statistical evaluation of the official milk recordingand breeding organisation in Austria indicates thatthe average milk urea content is around 20 – 22 mg100 mL -1 in the relevant milk yield classes (3000 –7000 kg milk) (Gruber and Poetsch, 2012).Researchers from United States use milk ureanitrogen (MUN) content for evaluation of theutilization of feed protein (Depeters et al., 1992). Milkurea nitrogen content makes 46% from the milk ureacontent (Spiekers and Obermaier, 2012). We estimatemilk urea nitrogen content for our study resultsfollowing the principles (Fig. 5).In the United States, normal MUN content in milkis from 8.0 to 12.0 mg dL -1 . In our study, farm A hadthe recommended MUN content, which suggests agood feed protein utilization in the farm. Farms B andD had a similar MUN content, which was higher thanthe normal content, whereas farm C had a two timeshigher MUN content than the norm, which indicatesthe problem with farm feeding or managementtechnology. The MUN content used for evaluation ofnitrogen utilization is more sensitive than urea content.The results of our study approval monitoringnitrogen utilization in the farms urea content areuseful to indicate problem with feeding managementand potential nitrogen loses.Conclusions1. It was established that milk urea content and yieldsignificantly (p