Calves with Sam

Brix Refractometer to Assess Colostrum Quality

An assessment of colostrum quality was done on 240/255 samples from 30 different dairy farms. 

The assessment methods were:

• digital Brix refractometer
• opitical Brix refractometer
• radial immunodifusion (RID) (laboratory method - used as reference standard)
• transmission infared spectroscopic

Of special interest to me was the comparison of the laboratory test (think of this as the "gold standard") and the two Brix methods.

The optimal cut off value for both the optical and digital Brix refractometers was 23% - pretty much as I expected from previous work. Recall that we are trying to exclude poor quality colostrum from the first feeding of newborn calves. With the optical and digital Brix refactometers at 23% this work reported correctly selecting "good" colostrum 80 percent of the time.

Compared to the laboratory test (RID) the Brix refractometer readings agreed 77 percent of the time. It was of interest to me to see that the two Brix methods had readings that agreed 98 percent of the time. 

Reference: Elsohaby, I and Others, "Rapid assessment of bovine colostrum quality: How reliable are transmission infared spectroscopy and digital and optial refractometers?" Journal of Dairy Science 100:1427--1435.