Nature of the Material in Milk Responsible for the Modified Whiteside Test for Mastitis

Abstract

Summary The evidence obtained in this study that leucocytes are directly or indirectly responsible for the Whiteside reaction in mastitic milk may be summarized as follows: The reaction in gravity-separated cream was stronger than in the whole milk; leucocytes have been shown to concentrate in gravity-separated cream. Cellular material, which produced a viscid mass when mixed with NaOH, was washed from cream separated from mastitic milk by gravity. Separator slime, which contained from 700,000,000 to 900,000,000 leucocytes per gram, always gave the most intense Whiteside reaction of any of the milk fractions obtained by mechanical separation. The curves showing the trend of the number of leucocytes, the amount of separator slime, and the intensity of the modified Whiteside reaction in samples of milk from a cow affected with mastitis of varying severity were closely parallel to one another. Addition of separator slime to Whiteside-negative milk produced a strongly positive milk and a large increase in leucocytes to about 2,600,000 cells per ml. The intensity of the Whiteside reaction of this mixture corresponded to that of other milk samples containing approximately 2,000,000 leucocytes per ml. Addition of either bovine or equine leucocytes to Whiteside-negative milk samples resulted in a change to positive reactions, the intensities of which varied directly with the number of leucocytes added. Addition of whole blood, blood plasma, blood serum, or erythrocytes to milk did not produce a positive test. Normal blood, which contained approximately 8,000,000 leucocytes per ml., reacted with normal NaOH in the ratio of 1:5; the appearance of the reaction in blood, however, could not be satisfactorily compared with that in mastitic milk. When a suspension of bovine blood leucocytes was mixed with normal NaOH on a glass slide, a transparent viscid gel could be detected. When one drop of normal milk was mixed into the gelatinous material, giving a white color to the mass, the appearance was that typical of the Whiteside reaction. Addition of leucocytes to Whiteside-negative milk, previously heated to 98° C. and cooled, resulted in a mixture which was strongly positive; addition of a suspension of leucocytes, heated to 98° C. and cooled, to negative milk did not make the reaction positive; the heating of negative milk which contained a suspension of leucocytes gave a negative reaction. It is postulated that the protein material of leucocytes in mastitic milk reacts with NaOH to form a gelatinous mass similar to that which is formed by the action of NaOH on nucleic acid from animal cells.