The effect of adding exogenous phytase to nutrient-reduced corn- and wheat-based diets on performance and egg quality of two strains of laying hens

A laying trial was conducted in which ISA-Brown and ISA-White hens were fed diets based on corn or wheat that had been pelleted to eliminate endogenous phytase. Control diets were formulated to contain adequate levels of all nutrients. Nutrient-reduced diets were formulated to account for nutrients released by the phytase. To formulate these diets, phytase was entered into the matrix with a value, on a weight basis, of 1,173% for CP (60.5% for lys, 29.4% for met plus cys, 40.0% for thr), 39 900 kcal kg (-1) for AME, 666% for Ca, and 333% for available P. A negative control diet was based on the modified formulation but did not include phytase. Differences between diets were observed for tibia ash, and Ca and P in the ash, as well as for BW and measures of egg quality. Egg production likely provided the best measure of the adequacy of P nutrition. In the final period of production, feed intake and egg production of hens fed the nutrient-reduced corn-based diet without enzyme was lower (P < 0.05) than that of hens on the control diet. Egg production of hens fed the nutrient-reduced diet with phytase was similar to that of hens fed the control diet, showing that inclusion of phytase permits formulation of corn-based diets with reduced levels of energy, CP, Ca, and P. No major effect of diet was seen for the hens fed wheat-based diets indicating that the formulation changes used may not have been appropriate for evaluating a response to exogenous phytase in wheat-based diets.