Assessment of colostrum quality using a refractometer

The mammary gland selectively concentrates antibodies (primarily IgG class and some IgM class antibodies) from the blood of the mare during the last two to three weeks of pregnancy. The mammary gland is capable of directly producing some IgA class antibodies that are found in colostrum. The average IgG concentration in equine colostrum is approximately 70 g/L (range:30 to 120 g/L). Evaluation of mare colostrum immediately after foaling and prior to nursing can be helpful in predicting if failure of passive transfer is likely to occur e.g. when colostrum has been lost due to premature leakage from the mammary gland, or if the colostrum quality is poor.

Refractometry measures the concentration of dissolved solids in a solution. Colostrum with a low amount of dissolved solids (i.e. low IgG level) will have a lower amount of light scatter and a lower percentage score. Colostrum with high amounts of dissolved solids (i.e. high IgG levels) will cause more light scatter and a higher percentage score.

The cost of a Colostrum refractometer test is approximately $2 (assuming the refractometer is used for 10 years).

Four samples of colostrums have been collected immediately post foaling from each of the four foals you assessed in the previous tests.

Procedure

1. Collect a small amount of one of the four colostrum samples (A, B, C, D) in a plastic pipette.
2. Two drops of colostrum are applied to the prism surface of the refractometer.
3. Close the plate; spreading the colostrum across the surface of the prism. View through the eyepiece while holding the refractometer in the direction of a light source.
   
   Note the level or location of the color (blue) on the scale. The Brix scale contains graduations (%) and a quality assessment score for accurate interpretation.
   
   
4. Evaluate the IgG Concentration range by consulting the table and recording the range.
5. After making a reading, wipe the prism surface with a KimWipe and irrigate with water. You can then assess the other three colostrums.

Interpretation