A SIMPLE-MODEL FOR PREDICTING THE RESPONSE OF CHICKS TO DIETARY ENZYME SUPPLEMENTATION

Two experiments with Leghorn chicks and data from five publications we re analyzed to determine whether a simple general equation could be us ed to predict the relationship between the amount of a crude enzyme ad ded to a diet and chick performance. The maximum improvements in weigh t gain and feed: gain ratio in Leghorn chicks fed rye diets containing different concentrations of enzymes were as high as 61 and 42%, respe ctively. Regression analyses demonstrated that there was usually a hig h linear correlation (r(2) > 0.9, P < 0.05) between the concentration of the enzyme when transformed into its logarithmic value and weight g ain or the feed:gain ratio. The general prediction equation was Y = A + B(logX), where Y is the performance value (i.e., weight gain, grams) , A is the intercept (y-axis), B is the slope of the line (change in p erformance per unit of enzyme in the diet), and X is the amount of enz yme in the diet. The slope of the line provides an index of the overal l efficacy of the enzyme treatment. The log-linear model shows that fo r every ninefold increase in amount of enzyme in the diet (i.e., when the amount was increased to 10 times the starting amount), there was o nly a doubling of improvement in chick performance. High correlations (r(2) values) were also obtained when data from the literature were an alyzed. The equation was applicable to different classes and ages of p oultry fed diets containing rye, wheat, barley, or lupins. These studi es demonstrate that there is a linear relationship between the amount of enzyme added to the diet, when expressed as a logarithmic value, an d the corresponding performance of chickens.