The accuracy and usability of the radial gel diffusion assay and a dye-release technique for determination of β-glucanase in feed

Two enzyme assays, the radial diffusion and the dye-release methods, were modified and tested for their suitability in measuring β-glucanase activity in poultry feed. Enzymes A and B were incorporated into a barley-based broiler starter diet at three levels (500, 1000 and 2000 g/t). The measured β-glucanase activities were 35 U/g and 49 u/g for Enzymes A and B, respectively. A comparison of enzyme recovery rates from samples containing known amounts of the enzyme and from a buffer solution containing the same amount of the enzyme revealed that a fixed percentage of the enzyme bound to feed components in a dose responsive manner. Thus, enzyme recovery rates for the feed samples were not complete and varied between 66% and 97% for the radial diffusion assay and between 76% and 91% for the dyerelease assay. The two assays largely agreed with each other although at low enzyme concentrations, the dye-release assays gave higher recovery rates with lower standard errors. It may be concluded that both assays are useful in determining β-glucanase activity in feed and digesta samples, but the radial diffusion assay is cheaper to perform.