Calf Care Quick Tip: Testing Total Proteins with a Refractometer

Testing total blood proteins can help you manage your colostrum program as this simple test indicates whether successful passive transfer is achieved.  Use the following steps as you test blood protein levels in your calves.

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.