At the present time, quality of FM is described only
by its solubility in 0.2% pepsin solution (Association of
American Feed Control Officials, 1994). Protein in FM
must be at least 75% soluble, using the in vitro test. A
more dilute solution (0.002% pepsin) has been tested as
a way to more accurately differentiate among the qualities
of FM (Johnston and Coon, 1979). Another procedure
was based on the use of acid detergent solution to solubilize
protein (Latshaw et al., 1994). Measurement of bulk