Pet Factsheets

Client Factsheets > Cattle > Brix refractometer

< Back to search

CONTRIBUTOR(S): Ash Phipps, Paul Wood,

Brix refractometer

Brix refractometer

The Brix Refractometer is an accurate and rapid cow-side method of measuring colostral quality. It works by light penetrating through a liquid (in this case colostrum) which causes the light to bend (or refract). The amount of bending can then be measured and correlates to the amount of protein in the sample. A large percentage of the proteins present in colostrum are antibodies (IgG) from the cow.


A Brix refractometer 
©Ash Phipps

How is the Brix Refractometer used?

1. Mix the colostrum thoroughly.
2. Place a small drop of colostrum onto the plate of blue glass using a pipette.
3. Place the daylight plate over the plate of blue glass.
4. Hold the refractometer up towards the light (the device measures the amount of light passing through the liquid).
5. Look through the eyepiece and read off the scale to the left of the field – your reading should be somewhere between 0 to 30%.
6. The reading you take is where the boundary line of blue and white cross the scale off to the left of the field.
7. Clean the plate of blue glass with a damp cloth and dry before storing away.

High fat content in some colostrum samples can result in a hazy line in the refractometer. Repeat the process above on the same colostrum to gain an accurate reading. If it remains fuzzy then take a reading from the middle of the fuzzy region.

What should the results be?

A good colostral sample should be > 22% (this equates to 50mg/ml of IgG).

Samples with readings below this level should not be given to calves under 24 hours of age, this can be retained and fed to calves that are older than 24 hours of age.

How do I calibrate a refractometer?

The refractometer should come with instructions as to how to look after it and how to calibrate it. Regular calibration will ensure accurate results. Manufacturer guidelines should be followed. If you do not have the manufacturer guidelines, then most refractometers may be calibrated as follows:

  • Ensure that the device is clean and dry.
  • Place 2 – 3 drops of distilled water on the plate of blue glass. (Do not use tap water.)
  • Place the daylight plate over the plate of blue glass.
  • Hold the refractometer up towards the light.
  • Look through the eyepiece and read off the scale to the left of the field.
  • The reading for pure water should be 0.0.  If necessary, turn the calibration screw (on the top of the device) until the boundary line (between the blue and white fields) is exactly on the 0.0 line. 

Brix refractometer results may be affected by ambient temperature and so it is worth calibrating regularly, particularly between seasons.

Scroll to top