Fütterungs- und nicht fütterungsbedingte Einflüsse auf den Milchharnstoffgehalt von Milchkühen – 3. Mitteilung: Vorschlag für ein dynamisches Modell zur Einschätzung der Rohproteinversorgung an Hand des Milchharnstoffgehaltes

Abstract. Title of the paper: The impact of nutrition and non nutrition factors on milk urea concentration. III. A new milk urea model to indicate the dietary crude protein / energy balance in dairy cows
The object of this study was to determine the impact of dietary crude protein / energy balance, stage of lactation, parity, milk protein yield, somatic cell count on milk urea concentration under the conditions of routine milk yield recording. From this data a model was created to predict the milk urea concentration for a single dairy cow or a feeding group. The relationship between dietary crude protein/energy balance, milk protein yield, stage of lactation, somatic cell count and milk urea concentration can be described by the following equation:

first lactation period y = 156.7 + 42.52 * milk protein yield + 0.34 * day in milk -0.017 * somatic cell count
second lactation period y = 186.2 + 43.23 * milk protein yield + 0.04 * day in milk - 0.019 * somatic cell count
third lactation period y = 188.3 + 31.17 * milk protein yield + 0.06 * day in milk - 0.015 * somatic cell count

The approximate confidence interval for a predicted milk urea content is ± 15 mg/l. If the analyzed milk urea concentration is greater than the predicted milk urea content (interval), this could indicate dietary crude protein excess. If the analyzed milk urea concentration is lower this might be due to a lack of dietary crude protein.