Evaluation of a Prototype On-Line Electrical Conductivity System for Detection of Subclinical Mastitis

¹ Department of Herd Health and Reproduction, Utrecht University, Yalelaan 7, 3584 CL Utrecht, The Netherlands
² IVO-DLO Institute for Animal Production, PO Box 501, 3700 AM Zeist, The Netherlands

A prototype on-line system for measurement of electrical conductivity of quarter milk was evaluated for accuracy in detection of subclinical mastitis compared with that of bacteriological culture and SCC of sampled quarters. Because of the low quarter prevalence of mastitis, quarters were sampled conditionally from the signals of the on-line system. All signaled quarters and a random selection of the nonsignaled quarters were sampled. To calculate sensitivity and specificity, the total number of nonsignaled quarters was extrapolated.

The system identified correctly 18 out of 23 subclinical quarters and 521 out of 555 healthy quarters. Quarter prevalence was about 1%. Predictive value of a positive test (35%) and the predictive value of a negative test (99%) were calculated, as well as sensitivity (25%) and specificity (99%), after extrapolation of the total number of nonsignaled quarters. Because of repeated measurements, sensitivity may be underestimated. When signaled quarters were defined by repeated signals within 14 d, predictive value positive increased to 48%.

The prototype on-line system did not detect subclinical mastitis very accurately because of suboptimal test characteristics.

Key Words: on-line electrical conductivity • subclinical mastitis detection

Submitted on August 30, 1993
Accepted on November 3, 1993

This article has been cited by other articles:

				E. Norberg, H. Hogeveen, I. R. Korsgaard, N. C. Friggens, K. H. M. N. Sloth, and P. Lovendahl Electrical Conductivity of Milk: Ability to Predict Mastitis Status J Dairy Sci, April 1, 2004; 87(4): 1099 - 1107. [Abstract] [Full Text] [PDF]