Phytase and protease supplementation for laying hens in peak egg production

Abstract

The effects of the combination of enzymes in commercial laying hens need to be more explored in literature. To determine if the type of protease affects performance, egg quality, nutrient intake, and morphometry of intestinal mucosa of laying hens in peak egg production and fed with phytase, 780 25-weeks Hy-Line W36 hens were assigned to a completely randomized design composed of five treatments/diets (one positive control, two negative controls, and negative controls plus protease A or B), with 12 replicates of 13 birds each. There was no effect of treatments (P > 0.05) on egg production, egg mass and feed conversion, even though the nutritional restriction imposed by the negative controls reduced egg weight (P = 0.02), albumen height (P < 0.01), and Haugh unit (P < 0.01). Although inclusion of proteases in negative controls did not cause the calculated intake of protein and amino acids to return to the same amount consumed by positive-control hens, egg quality parameters returned to positive control standards with protease A. Intestinal mucosa responded to treatment only at jejunum, where birds fed with protease B showed greater (P < 0.01) villus height and crypt depth than those treated with protease A. These findings suggest that different proteases and phytases interact distinctly and, in consequence, induce different responses on the birds. Moreover, the behavior of egg quality parameters after protease A inclusion in the diet indicates that the nutritional contribution of the combination of this protease with phytase is greater than the contribution of protease alone.