Beurteilung der Versorgungslage von Milchkühen in der frühen Laktation anhand der Milchinhaltsstoffe

For the on-farm assessment of protein and energy supply of dairy cows, specific management tools based on milk protein and urea content are used. In order to determine the degree of agreement between estimates from the so-called 9-fields table or the updated 6-fields table and the actual protein and energy supply, data from a feeding trial were used (chi-square fit test, sensitivity, specificity and likelihood ratios). The optimum supply range for both crude protein and energy was defined within ±10% of daily requirement. For the first ten weeks of lactation the proportions of correct estimates were 17.2% and 27.6% for the 9-fields and the 6-fields table, respectively. Sensitivity ranged from 0.00 to 0.50 and from 0.00 to 0.56, respectively. In addition, the false assessments were compared with their effective classification. It was found that these are not always located in the adjacent fields. Therefore a mere adaptation of thresholds for milk urea, milk protein or the fat to protein ratio will not substantially improve the reliability of the assessment. Due to the high proportions of seriously false estimates, the tools tested in the present study cannot be recommended for assessment of energy and protein supply of individual dairy cows.