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Why use a refractometer to measure colostrum?

Did you know that using a refractometer is one of the simplest and best ways to determine the quality of colostrum for new-born livestock?

Using an OPTi Digital Handheld Refractometer pre-programmed for colostrum quality, you can obtain results within seconds!

Receiving quality colostrum is imperative to newborn livestock including foals, lambs and calves, as it is rich with antibodies (or immunoglobulins). Livestock born with low levels of immunoglobulin are in danger of becoming immunologically compromised and can be, at times, in a potentially life-threatening position at birth.

For the healthiest start to life, and to provide the nutrients that a newborn needs, it is imperative that the first feed be of good quality, with a sufficient colostrum supply available for your livestock.

Using a refractometer to monitor colostrum quality fed to newborns can help to ensure that these young animals receive enough immunoglobulin, increasing the survival rate of new livestock. 

What is “Good” colostrum?

 What do we mean by “good” quality colostrum? Well, it is broadly accepted that a sample of good quality colostrum contains 50g IgG/litre of colostrum though not all stock will produce to this level, this is why it is important to test across the farm to ensure a high quality first feed.

Colostrum quality conversion table


IgG Conc. g/l

Colostrum Quality












Very Good


Why use a refractometer to measure colostrum?

Testing with a colostrometer (a hydrometer that uses the correlation between colostrum density and IgG concentration to give a measure of quality) is possible but can be impacted by temperature or by dry matter within the sample. Accuracy with temperature is key and will need samples of 20-21 °C to measure reliably. Refractometers are not dependant on temperature for accurate measurement of colostrum so are preferred by many.

OPTi Digital handheld refractometer for colostrum

The quickest and simplest method for colostrum quality measurement is by using an OPTi digital refractometer. This pocket sized handheld device only needs a tiny amount of sample to give you a reading. All you need to do is apply the sample to the prism dish & press “READ”. It really is that simple!

Unlike other methods of measurement there are no look-up tables or conversions necessary, the OPTi will do the hard work for you, before telling you in plain English whether the sample is good to use or not.

The OPTi Digital Handheld Refractometer for colostrum also comes with 2 additional pre-programmed scales: Total Solids of Waste Milk, and Brix. These scales can be used when needed, or swapped at any time thanks to the onboard library of 50 common refractometer scales.

Eclipse optical refractometer for colostrum

The Eclipse handheld refractometer is an optical tool designed to measure refractive index, which is then converted into a concentration measurement – in this case colostrum quality. To use, place a small drop of your colostrum sample onto the glass prism, close the flap and look through the eyepiece. The results will be shown by a shadowed line through the scale. We call this the borderline. By referring to the colostrum conversion table, you’ll be able to tell if the sample is poor, adequate or very good.

Remember: the use of a refractometer allows the level of immunoglobulin to be assessed quickly (in seconds) and effectively and immediate treatment can follow. The refractometer is an invaluable and simple aid to securing these measurements without the need for large, valuable amounts of sample.

To learn about Eclipse and OPTi refractometer click here.