Editor’s Note: Dr. Olson is technical services veterinarian for Milk Products, LLC. For more information, contact him at 920-216-7612, [email protected] or visit calfsolutions.com.
Remember experimenting with prisms in middle school science class, casting rainbows all over the classroom? Those fun tools, which separate different wavelengths of light, are the main components of refractometers.
Veterinarians have been using Brix refractometers for many years to assess concentrations of liquids like blood serum and urine. Others use refractometers as a quality-control tool for processing liquids such as wine, beer, maple syrup, honey and apple cider. Now, this convenient, hand-held tool is being adopted widely by calf raisers to improve consistency of colostrum and waste milk.
Refractometers work by measuring the degree of bending of light through a liquid sample placed on a prism. As the concentration of a liquid increases, so does the degree to which the light is bent or refracted.
A Brix refractometer assesses the percent of sucrose, or sugars, in a solution, measuring in “degrees Brix.” “Brix” is not a brand name, but rather, a specific measurement of sucrose content. One degree on a Brix scale is equal to 1 gram of sucrose in 100 grams of solution.
Colostrum quality control
Many calf raisers use visual appraisal and volume of first-milking colostrum to assess colostrum quality. Despite these evaluations, research has shown colostrum from one cow to the next can range in IgG content – from as low as 20 mg/mL IgG to as high as 100 mg/mL. Without assessing IgG levels, calf raisers risk failure of passive transfer of immunity in newborn calves.
A Brix value of 22-23 has been shown to correlate with 50 mg IgG/mL, which is often used as the cut-off point for high-quality colostrum. The reading can easily be taken as colostrum is harvested since many models of refractometers compensate for temperature. It is highly valuable in separating high-quality colostrum from low-quality colostrum, thus giving every calf the opportunity for successful passive transfer of immunity.1
Waste milk consistency
More recently, dairy producers have started using Brix refractometers to help improve the consistency of waste milk fed to calves, which has been shown to promote preweaned calf growth.
Over time, the industry has learned the importance of delivering a consistent, high-quality product to young calves. That’s also why pasteurization, to kill bacteria in waste milk, has become such a widespread practice. Likewise, on-farm studies have shown the solids content of waste milk can be highly inconsistent.
Washington State University researchers evaluated the solids content of samples from several batches of waste milk sold to a large western calf ranch. They found that solids levels varied widely from the standard level of 12.5 percent for whole milk. In a few cases, solids levels were higher than 12.5 percent, likely due to colostrum or transition milk included in the waste milk. But many more samples were below 12.5 percent, dipping to as low as 6.7 and 5.1 percent, respectively, for two samples.
Calves fed waste milk low in solids may not receive adequate nutrition for optimal growth and health. The likely cause of low solids levels in waste milk is added water. Often, waste milk is not handled as carefully as salable milk, and wash water may inadvertently be mixed with it.
Researchers at Washington State University determined a Brix refractometer can be helpful in assessing solids level in waste milk, but the Brix reading underestimates the solids percentage by about 2 points. So, the standard conversion for waste milk is “Brix-plus-2.” In other words, if the Brix refractometer reads “10,” the solids level of the sample is 12 percent.3 Brix readings should always be taken using raw, unhomogenized, whole milk before it is pasteurized.
Pasteurized milk balancer products can be used to boost solids levels in waste milk. Based on the prepasteurization Brix reading, a simple calculation process can determine the amount of balancer and water needed to achieve the desired consistency. Balancers are preferred over standard milk replacer powder for this purpose. They typically contain a higher level of protein which is used to raise the level of protein that is diluted when water is added to the whole milk in the effort to lower the total fat in the milk.
It is important to note that a Brix refractometer is not as precise in evaluating solids in waste milk after it has been fortified with balancer powder, or in reconstituted milk replacer. Solutions with powder added to them do not refract light as consistently as unpasteurized whole milk. However, a Brix refractometer can be used as a quality control measure to assess mixing consistency of milk replacer solutions.
Choosing and caring for Brix refractometers
Brix refractometers can range in price from $100 to several hundred dollars. A unit with a Brix scale of 0 to 35 should be sufficient for colostrum and waste-milk testing.4 Digital Brix refractometers are preferable because they can leave less interpretation of results.
Finally, be sure to purchase a model with automatic temperature correction (ATC), which will deliver more consistent results regardless of the temperature of the solution being tested. This feature costs a little more, but is worth it when you consider the temperature variation that can occur day-to-day – testing fresh colostrum that still may be warm or waste milk that may be chilled.
Be sure to clean the prism after every use by wiping it off with eye glass cleaner and wipes that won’t scratch the prism. Return the Brix refractometer to its case after every use to avoid damage and to keep it clean. While they are sturdy tools, they are not indestructible. Calibrate the refractometer periodically with distilled water, which should provide a Brix reading of “0.”
Your veterinarian or calf nutritionist can be a helpful resource in choosing a Brix refractometer, and putting it to use on your farm for more consistent colostrum delivery and calf nutrition from whole milk.
1, 4 – Heinrichs, J. and C. Jones. 2016. Colostrum management tools: hydrometers and refractometers. Penn State Extension Bulletin.
2, 3 – Moore, D. A. et al. 2009. Quality assessments of waste milk at a calf ranch. Journal of Dairy Science. 92:3503-3509.