Measurement of neonatal equine immunoglobulins for assessment of colostral immunoglobulin transfer: comparison of single radial immunodiffusion with the zinc sulfate turbidity test, serum electrophoresis, refractometry for total serum protein, and the sodium sulfite precipitation test.

Four procedures for assessment of adequacy of colostral immunoglobulin (Ig) transfer in foals were evaluated. Results of zinc sulfate turbidity test, serum electrophoresis, total serum protein refractometry, and sodium sulfite precipitation test were compared with immunoglobulin G content determined by single radial immunodiffusion. The zinc sulfate turbidity test gave acceptable results for IgG, except that hemolyzed serum samples gave higher than expected values. A correction factor for hemolyzed serum was found to be useful. Serum electrophoresis was a satisfactory method of estimating IgG content. Total serum protein values may not be a valid basis for estimating IgG content, inasmuch as postsuckling total protein values were found to decrease in some foals in which passive transfer of IgG had been adequate. Sodium sulfite precipitation reactions were too unpredictable to be of value for determination of neonatal IgG concentration.