An adequate supply of newborn calves with antibodies from the maternal colostrum within the first hours of life is essential, because as a result of the structure of the bovine placenta, only insufficient transfer of antibodies from the cow to the calf can take place during pregnancy. This investigation set out to determine wether, levels of three diagnostic parameters - diagnostic parameters immunoglobulin G serum concentration (IgG), total protein serum concentration (STP) and gamma-glutamyltransferase activity in the blood (GGT) – measured in the blood of new born calves could be related to subsequent illness in the first three weeks of life. In addition, we checked whether the limit values of these parameters published in the literature can be used in on-farm conditions. Blood samples were taken from a total of 200 German Holstein calves 24 to 26 hours p. n. at three dairy farms. The calves were segmentally examined for 14 days and 21 days p. n. and the state of health was documented. Three animals were excluded, leaving a sample size of 197. The concentrations of immunoglobulin G in serum were detected by means of an ELISA. The total protein serum concentration was determined refractometrically and the activity of gamma-glutamyltransferase in the serum of the calves was determined photometrically. The data were evaluated using a ROC curve. The values determined by laboratory diagnostics were related to their respective animal’s state of health on the 14th or 21st day p. n.. The animals were divided into five groups (all animals, all female animals, all male animals, all female and drenched animals, all female and undrenched animals). The evaluation of the collected data took place on the basis of an ROC curve. The following results were achieved: The cutpoints of 21.9 mg/ml IgG (14 days p. n.) and 21.8 mg/ml IgG (21 days p. n.) for serum IgG concentrations had a sensitivity of 54.39 % and 42.11 %, respectively, and a specificity of 60.74 % and 57.52 %, respectively. These values refer to the calculations for the total population. By means of differentiated calculations for defined groups, own cutpoints could be calculated. These did not lead to a significant improvement in sensitivity and specificity. Based on the results of the statistical evaluation, immunoglobulin G cannot therefore be defined as a suitable predictor for disease under on-farm conditions. Limit values for the serum IgG concentration (5 mg/ml, 10 mg/ml and 20 mg/ml) necessary for sufficient passive immunity selected from the literature could also not be demonstrated as suitable limit values. According to the calculations, the determined limit values for the TP serum concentration were 5.4 g/dl for the entire population. The corresponding sensitivities were 54.39 % and 36.84 % respectively and the specificities were 66.67 % and 60.13 % respectively. The calculations for the subpopulations provided their own limits, which in turn did not lead to a significant improvement in sensitivity and specificity. The selected limit values from the literature (5.0 g/dl, 5.5 g/dl, 6.0 g/dl) could not be confirmed as suitable. The detected limits for the activity of gamma-glutamyltransferase, based on the total population, were 790 IU/L (14 days p. n.) and 920 IU/L (21 days p. n.). The corresponding sensitivity was 64.91 % and 65.79 % respectively and the specificity was 51.85 % and 41.83 % respectively. The cutpoints determined by calculations for subpopulations did not lead to a significant improvement in sensitivity and specificity. The limit value of the activity of gamma-glutamyltransferase in the serum of calves suggested by the literature was 200 IU/L. This could not be confirmed as a suitable parameter. The serum activity of gamma-glutamyltransferase could not be demonstrated as a suitable parameter for predicting the disease probability of calves in the first 3 weeks of life. In summary, in the investigated population under realistic conditions, no suitable limit value for the immunoglobulin G serum concentration, the total protein serum concentration and the gamma-glutamyltransferase activity in calves‘ blood 24 - 26th hours p. n. could be determined to predict the probability of disease in the first 21 days of life. Neither could the limit values published in the literature be verified as useful under field conditions.weiterlesen