ICAR Technical Series no. 7 - Nitra Proc.

Kroemker et al.were calculated using the principle of least probability of misclassification(PM) (Krömker et al., 1998). The diagnostic test criteria sensitivity,specificity, and PM were determined with Win Episcope 2.0 ® (Epidecon).The data of 96 cows with 382 quarters was used in the present study. Udderhealth of animals and quarters involved was determined at the beginningof the survey on both farms, with constant monitoring during the trial.Table 2 shows the prevalence of mastitis at the onset of the investigationfor both production systems.ResultsUdder health was defined by SCC less than 100,000 cells/ml and theabsence of pathogenic bacteria in foremilk samples (DVG, 1994). By thisdefinition merely six animals were considered as udder-healthy on allquarters throughout the whole lactation. The physiological developmentof quarter milk yield and electrical conductivity during lactation is depictedin figure 1.During the survey, 684 new cases of sub-clinical mastitis (NS becoming Mor UM) and 44 clinical cases of mastitis were recorded. In order to assurecomparability, a similar number of non-disease cases (NS remaining NS)was used along with the new cases.Because of the retrospective analysis of the electrical conductivity andquarter yield data, thresholds for the individual parameters and acombination of both were established separately. Analysis methodsassociated with ‘moment’ and ‘time’ were also tested. Those associatedwith the momentary survey considered only the actual value, whereasthose associated with consecutive survey compared the actual value withthe preceding values. Table 3 presents the methods of analysis employedin the present study, along with their thresholds; table 4 shows theircorresponding values for sensitivity, specificity and PM.The results of the analyses show that between 12 and 70 % of all newlydiseased quarters can be readily identified, using these parameters. Thecombination of different thresholds increases the sensitivity. In particularit is interesting that the decrease of relative quarter yield from one samplingto the subsequent one by 10 %, alone and in combination with otherparameters is the method with the best identification rates. The specificityTable 2. Udder health status (%) at the onset of sampling.Farm NS LI UM M1 (n = 54 cows) 27,8 / 68,2* 3,7 / 1,9 55,6 / 25,7 13,0 / 4,22 (n = 42 cows) 35,2 / 70,2 7,1 / 3,0 31,0 / 18,5 26,2 / 8,3*= The first value refers to the cows, the second to the quarters.ICAR Technical Series - No 765