Using a Brix Refractometer to Test Colostrum
The results of a study suggest using two criteria for assessing colostrum quality.
"Based on this study, the 2 cut-points could be alternatively used to select good quality colostrum (sample with Brix greater than or equal to 22%) or to discard poor quality colostrum (sample with Brix less than 18%). When sample results are between these 2 values, colostrum supplementation should be considered." [S. Buczinski and J. M. Vandeweerd, "Diagnostic accuracy of refractometry for assessing bovine colostrum quality: A systematic review and meta-analysis." Journal of Dairy Science 99:7381-7394 Sept 2016]
This two-cut point idea maintains the upper value that has been published in the dairy magazines in the past few years - greater than or equal to 22 percent. At or above this value it's okay to use for first feeding as fresh or frozen.
So what is different? Well, they are saying that on one hand there is enough uncertainty about the Brix values that tossing out anything below 22% can result in discarding a fair amount of pretty good colostrum.
On the other hand if the test value is below 18% the chances of correctly classifying this colostrum as poor are quite high - few mistakes.
Thus, we end up with the colostrum between 18 and 22% that may be important to fill our needs. I feel this is good stuff to feed as second or third feeding. If it has to be fed as first feeding their suggestion of using a colostrum supplement is good advice.