Evaluating the efficacy of enzyme preparations and predicting the performance of leghorn chicks fed rye-based diets with a dietary viscosity assay

Department of Animal Science, University of Manitoba, Winnipeg, Canada.

We studied whether a single-step dietary viscosity assay could be used to evaluate the efficacy of an enzyme when added to a poultry diet. The results demonstrated a linear relationship between the log of the dietary viscosity change in vitro, as determined with the new assay and the log of the enzyme activity (xylanase) added to a rye-based diet. The sensitivity of the dietary viscosity assay was high, as little as 0.19 U of xylanase per gram of diet could be detected. In addition, there was a high correlation (r > or = 0.97; P < 0.005) between chick performance and the log of the amount of enzyme added to the diet or the log of its viscosity change in rye-based diets that contained different amounts of xylanase, as determined by the in vitro dietary viscosity assay. Further, the dose response data from the dietary viscosity assay, when incorporated into a log-linear model that we developed, was able to distinguish between the efficacy of two enzymes with regards to their ability to hydrolyze the viscosity factor in rye grain. Therefore, it was possible to accurately evaluate the efficacy of enzyme preparations in a rye diet and to predict chick performance using the new assay in conjunction with a model equation.