An Investigation of the Suitability of Viscosity Detection in Estimating IgG Content in Mare Colostrum.

An adequate supply of colostrum is important for the prevention of hypogammaglobulinaemia in foals. In addition to the quantity of colostrum consumed and the time of consumption, the quality of the colostrum, the immunoglobulin (Ig) G concentration, is crucial. The aim of this study was to determine whether the viscosity of equine colostrum was a suitable estimate of IgG concentration. IgG content of colostrum was measured by ELISA and viscosity directly measured with a cone plate viscometer and indirectly assessed with a funnel. Analysis of 56 colostrum samples obtained from 40 mares at different postpartum time points was conducted to assess colostrum samples with varying levels of quality. The range of IgG concentrations determined by ELISA was 0.83 to 245.5 mg/mL (30.69 ± 41.92 mg/mL). The range of viscosity values determined by the cone plate method was 1.84 to 110.00 cP (7.86 ± 17.48 cP) at a shear rate of 3 rpm. Colostrum drainage from the funnel (drainage time), varied between 7.9 and 30.0 s, with an average of 9.96 ± 4.48 s. As the data were not normally distributed, Spearman's rank correlation analyses were calculated and significant correlation found between viscosity and IgG content (ρ = 0.71, P < .001), as well as between drainage time and IgG content (ρ = 0.75, P < .001). These correlations indicate that determining the viscosity of equine colostrum by cone plate or drainage time, may be an effective proxy measurement of IgG content.

Comparison of Different Methods to Determine the Absorption of Colostral IgG in Newborn Foals.

The timely diagnosis of abnormalities in the passive transfer of colostral immunoglobulins is important for the health and development of newborn foals. This study investigated three different methods for measuring immunoglobulin G concentration in neonatal foals. Comparison of a commercial SNAP assay, total protein concentration determination, and total globulin calculation by subtracting the albumin fraction from total protein as an indirect parameter was performed on a quantitative ELISA, which served as a reference method. The study included 119 samples from 148 foals between the age of 1 and 6 days. A blood concentration of 800 mg/dL was considered to indicate adequate absorption of immunoglobulins, and a concentration of less than 400 mg/dL was considered to be hypogammaglobulinemia. The sensitivity of the SNAP test was 64.5% and specificity was 94.7% for diagnosing sufficient absorption of immunoglobulin G at a value of 800 mg/dL. A value of 54 g/L was found to be most appropriate for the use of total protein and provided a sensitivity of 67.3% and specificity of 84.2%. For total globulins, the most appropriate value was 27 g/L, which yielded a sensitivity of 74.5% and specificity of 81.6%. At values under 400 mg/dL, the sensitivity of the SNAP test was 89.4% and the specificity was 83.0%. Here, the most suitable value for the total protein was 51 g/L. This provides a sensitivity of 65.2% and a specificity of 76.8%. The most suitable concentration for the use of total globulin was determined to be 24 g/L, which provided a sensitivity of 75.8% and a specificity of 78.1%. The study and its results show that the SNAP test, the TP, and the TP-A method perform similarly well compared to the ELISA in determining IgG concentration of ≥800 mg/dL. Based on the 95% confidence intervals, however, the Snap test and the TP-A method appear to perform similarly well but better than the TP approach for IgG concentrations <400 mg/dL.

[Immunoglobulin concentration in equine colostrum and blood of newborn foals as well as clinically relevant IgG evaluation methods - An overview]. / Immunglobulinkonzentration im equinen Kolostrum und im Blut neugeborener Fohlen sowie klinisch relevante IgG-Bestimmungsmethoden.

Due to the special structure of the equine placenta, foals depend on an adequate intake of high-quality colostrum post natum in order to ensure the development of passive immunity. The quality of the colostrum is determined, among other things, by the IgG content. This may be evaluated in the colostrum by direct and indirect methods (density and refractive index). The density of the colostrum is measured by a colostrometer and should amount to at least 1060 g/l. Refractometry is suitable for assessing the relative density or refractive index. Good equine colostrum has a Brix value of at least 23 %. The IgG concentration in the blood of the foal may also be determined by direct and indirect methods. The SNAP®-Test is regarded as a direct semi-quantitative measurement method, with values > 800 mg/dl indicating an adequate IgG concentration. Furthermore, the radial immuno-diffusion test, the latex agglutination test, and the immunoturbimetry are direct methods that may be applied. Indirect methods include the zinc sulphate turbidity test, the glutaraldehyde coagulation test, as well as the measurement of total protein, globulin concentration and γ-glutamyl transferase activity.