Electrophoretic studies on milk I. Investigations on colostrum of dairy cows

Electrophoresis tests were carried out on samples of colostrum of dairy cows. The milk was first cleared by dialysis against Michaelis veronal-sodium buffer (pH = 8; μ = 0.1) and high-speed centrifuging. The results of chemical fractionation by the method of Rowland show an increase in the casein, in the samples from cow A, from 42.1 to 82.8%; with cow B from 29.7 to 81.0%. Together with this increase in casein content there is a drop in globulin content during the colostrum period from 41.7 to 4.5% with the samples of cow A and from 61.2 to 6.4% with cow B. In the electrophoresis (pH = 8; μ = 0.1; t = 2° C; I = 25 mA) the same number of fractions were obtained as with normal milk, but in different proportions. From the results obtained it appears that the B component, of mobility 7.5 · 10 −5 , rises during the colostrum period from 21.8 to 51.8% and from 11.9 to 48.6% respectively for the samples from cow A and B. The G component also, of mobility 3.6 · 10 −5 , rises during the colustrum period, i.e. from 9.0 to 14.7% in the samples from cow A, and from 6.5 to 18.4% with cow B. As we were able to establish previously from the results obtained in the electrophoresis of normal milk, the B and G components show a casein character, which is also confirmed by the results obtained with colostrum milk. Moreover, during the colostrum period there is a considerable drop in the H component, the slowest moving fraction with a mobility of 1.9 · 10 −5 . With the samples from cow A this drop is from 46.9 to 3.3% and with cow B from 59.2 to 4.2%. On account of the remarkable agreement between the globulin percentage and the magnitude of the H component, we ascribe a globulin character to this fraction. The other components A,C,D,E and F show only slight variations during the colostrum period.