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 ± 2.46 g/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 ≥125 g/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 ≥125 g/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.