The diagnostic accuracy of the Brix refractometer in determining mare colostrum with high and low immunoglobulin G concentrations.

Abstract

Background: Foals, that receive poor-quality colostrum, are exposed to a risk of failure of transfer of passive immunity. The Brix refractometer can be used for the estimation of the immunoglobulin (IgG) concentration of mare colostrum, yet there is a scarce literature available on Brix refractometer thresholds for use in the detection of mare colostra with high and low IgG concentrations.

Aim: This study aimed to assess the diagnostic accuracy of the Brix refractometer in determining mare colostra with IgG concentrations of <50g/L, <60g/L, >80g/L, >100g/L and >125g/L.

Materials and methods: Two hundred and seventeen Arabian mares had colostral IgG concentrations measured with the radial immunodiffusion assay and estimated with the Brix refractometer. Brix thresholds were determined by performing a receiver operating characteristics analysis.

Results: The mean colostral IgG concentration was 83.73±2.46g/L and colostral IgG concentrations had a high correlation (Pearson's r=0.78) with Brix percentages. The optimal refractometer thresholds for the determination of colostral IgG concentrations of <50, <60, >80, >100 and >125g/L were ascertained to be <19.6%, <20.1%, >21.6%, >23.6% and >27.3%, respectively. The sensitivity and specificity of the Brix refractometer for the determination of colostral IgG concentrations of <50, <60, >80, >100 and >125g/L were found to be 89.3%(95%CI:71.8-97.7%) and 83.8%(95%CI:77.5-89.0%); 82.0%(95%CI:68.6-91.4%) and 88.1%(95%CI:81.8-92.8%); 85.3%(95%CI:76.9-91.5%) and 73.7%(95%CI:63.9-82.1%); 84.8%(95%CI:73.0-92.8%) and 76.1%(95%CI:68.2-82.8%); and 75.0%(95%CI:53.3-90.2%) and 90.4%(95%CI:85.1-94.3%), respectively.

Conclusion: the digital Brix refractometer showed a good performance in determining mare colostra with low and high IgG concentrations.