Improving the utilization of crude protein is subject of many studies because of its economic impact on the animal and poultry industries and detrimental effects of nitrogen excretion to the environment.  Protease supplements have been suggested to potentially achieve increased prececal amino acid digestibility in broiler chickens, and thereby allowing reducing the crude protein level in the diet.  The effects of protease supplementation on prececal crude protein and amino acid digestibilities have been found to be inconsistent.

The objective of this study was to determine the effects of protease products on the prececal amino acid digestibility and the influence on composition of the microbial community in the small intestine.   Treatments considered of three protease products added to the corn-soybean meal basal diet at the level recommended by the supplier and at an 8-fold level.   Each dietary treatment was allocated to 8 replicates of 15 birds each.  The results of this experiment showed that the effect of protease supplementation on the prececal amino acid digestibility depended on the protease product type and the amount supplemented.  The amino acid digestibility of the corn-soybean meal diet was significantly increased by one protease product when supplemented at high level and when phytase was supplemented.  In all the other treatments, protease supplementation had no significant influence or it decreased prececal amino acid digestibility.