Problems associated with the milk ring test

Decolorization induced by bacterial growth after long incubation periods could affect the strength of the reaction and subsequent interpretation. 3
The MRT was subject to nonspecific reactions caused by testing colostrum or milk from cows with mastitis. 4
In addition to the subjective nature of the test it was also recognized that results were dependent on the ability of laboratory personnel to read the test correctly. 5
It was known that antibodies against cross reacting organisms would produce reactions in the MRT resulting in false positives. 8
MRT depends on the presence of cream, making the test difficult to perform. The cream content varies with individual animals and would be diluted with pooled or bulk tank samples. 16
Partial freezing of negative milk could result in weak nonspecific reactions. 16
Animals vaccinated as calves produced weak reactions upon maturity. 23