Estimation of bovine colostral immunoglobulins by refractometry

The total protein of colostral whey from dairy cows as determined by a refractometer were compared with the immune globulin concentration obtained by cellulose acetate membrane electrophoresis and the immunoglobulin (IgA + IgG + IgM) contents determined by radial immunodiffusion. The coefficient of correlation between the results obtained by refractometry and electrophoresis was 0.98 (P < 0.001). The correlation between refractometry and radial immunodiffusion was 0.89 (P < 0.001), while that of electrophoresis and radial immunodiffusion was 0.87 (P < 0.001). Refractometry can be used as a simple, fast and inexpensive indirect method of assessing immunoglobulins in colostral whey.