Calf Care Quick Tip: Testing Total Proteins with a Refractometer
Collecting the sample
- Use a red-top serum collection tube (no anti-coagulant added), vacutainer or 3-cc syringe with 20 g 1-inch needle.
- Draw 2 to 3 mL of blood from the jugular vein in calves two to five days of age. Ideally, draw blood one to two hours after the first milk or milk replacer feeding.
- Let the blood sample sit at room temperature for 12 to 24 hours OR let it sit at room temperature for at least 30 minutes and then spin it in a centrifuge for 10 minutes.
Testing with an optical refractometer
- Calibrate the refractometer according to the manufacturer’s instructions.
- Pipette the serum from the tube, making sure you do not collect the clot or any red blood cells.
- Place a drop of serum on the optical surface.
- Lower the lid over the glass and look through the eye piece to determine the concentration of total serum protein.
Testing with a MISCO refractometer
- Calibrate the refractometer daily.
- Select “read total protein” from the refractometer menu.
- Pipette a small amount of serum and place a few drops on the center well.
- Close the lid, press the read button, and wait a few seconds to get the results.
Download this Refractometer How-to Guide for more details on selecting, using and cleaning refractometers.
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