An evaluation of a hand-held electrical resistance meter for the diagnosis of bovine subclinical mastitis in late lactation under Australian conditions.
OBJECTIVE
To assess the ability of a hand-held device to differentiate between infected and noninfected bovine mammary glands according to the electrical resistance of milk, under Australian conditions.


METHODS
A cross-sectional study.


METHODS
Milk samples were collected from 236 quarters of 60 cows selected from a commercial dairy herd with a high prevalence of mastitis. The true infection status of these quarters was determined using bacteriology. Various methods were used in an attempt to relate the electrical resistance of milk from each quarter to the presence or absence of infection in that quarter.


RESULTS
Although the electrical resistance of milk from infected quarters was generally lower than that of noninfected quarters, the overlap of readings between the two populations limited the ability of this device to indicate accurately whether a quarter was infected. The use of methods comparing the readings from each of the four quarters of a single cow did not allow the reliable detection of infected cows.


CONCLUSIONS
Although this device may have some practical advantages in comparison with some other methods of diagnosing subclinical mastitis, the predictive value of the method was generally poor.
Seguya
A G
AG
University of Melbourne, Werribee, Victoria.
Mansell
P D
PD
D000818:Animals; D001315:Australia; D002417:Cattle; D003430:Cross-Sectional Studies; D017097:Electric Impedance; D005260:Female; D007774:Lactation; D008414:Mastitis, Bovine / Q000175:diagnosis* / Q000503:physiopathology; D008892:Milk / Q000382:microbiology* / Q000502:physiology; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D013290:Streptococcal Infections / Q000175:diagnosis / Q000503:physiopathology / Q000662:veterinary*