Evaluation of three enzymic methods as predictors of in‐vivo response to enzyme supplementation of barley‐based diets when fed to young chicks

The β‐glucan degrading ability of several commercial crude enzyme preparations was determined using three different assay procedures. The assays were based on the ability of the enzymes to reduce the viscosity of a β‐glucan solution, to produce reducing sugars from β‐glucan or to produce a blue‐coloured solution upon hydrolysis of azo‐barley‐glucan. Regression analysis showed that the relationship between the relative improvements in weight gain of chicks fed a barley‐based diet that was supplemented with different concentrations of different enzyme and in‐vitro enzyme activity when the azo‐barley‐glucan and reducing sugar assays were used was quadratic. A linear relationship was observed for the viscosity method. The R 2 values for both weight gain and feed to gain ratio were highest for the azo‐barley‐glucan method but the other methods yielded similar values under appropriate assay conditions (ie concentration of enzyme). The azo‐barley‐glucan method, nevertheless, is the assay recommended as it is by far the simplest of the three assays and it yields a low coefficient of variation.