Brix refractometer scoring of immunoglobulin G in postpartum mares’ colostrum

Abstract

Newborn foals are dependent on ingestion of high-quality colostrum for their immune protection. Colostrum quality (immunuoglobulin G [IgG]) can be determined by the single radial immunodiffusion (SRID) test or estimated by Brix refractometer. Goal was to compare SRID test findings (IgG concentrations) and Brix refractometer readings (IgG percentage) in colostrum samples collected from mares during the first 12 - 18 hours postpartum. A total of 56 colostrum samples were collected from 10 postpartum mares. Postfoaling, colostrum IgG concentrations were 21,785 ± 5,592 mg/dl and IgG percentage was 27.9 ± 3.7%. At 12 hours postfoaling, IgG concentrations decreased to 1,713.9 ± 1,380.4 mg/dl and its percentage to 11.4 ± 1.6%. There was a high correlation (r = 0.9661) between SRID test results and Brix refractometry scores. In summary, Brix refractometry can be used to monitor colostrum quality.