Time-course levels of alpha 2-macroglobulin and albumin in cow colostrum and milk and alpha 2-macroglobulin levels in mastitic cow milk.

Time-course levels of alpha 2-macroglobulin and albumin in cow's colostrum and milk during lactation were investigated in order to obtain data that could help to elucidate the biological role of alpha 2-macroglobulin in mammary secretions. Levels of these proteins were also studied in mastitic cow milk and were related to the degree of mastitis, which could allow its use as a mastitis marker. The highest concentration of alpha 2-macroglobulin was found in the first milking (386.7 micrograms/ml). This value decreased very rapidly during the colostral period, attaining its definitive value during the 2nd wk postpartum (4.5 micrograms/ml). The albumin/alpha 2-macroglobulin ratio increased by 6.8 in the first milking to 44.4 at 2 wk postpartum, indicating that the increase of alpha 2-macroglobulin was greater than that of albumin. In mastitic cow's milk, the concentration of alpha 2-macroglobulin (48.1, 71.4, and 89.0 microgram/ml) was also higher than that in normal milk. This increase was found to be related to the degree of mastitis as determined by the California Test.