The activities of amylase and a trypsin-like protease in the gut contents of germ-free and conventional chickens.

1. Proteolytic and amylase activities were assayed in the gut contents of germ-free and conventional chickens aged 3 and 14 d. 2. The tendency was for the proteolytic activity to be increased and the amylase activity to be decreased in conventional chicks. These differences were statistically significant in the caecum. 3. All of the additional proteolytic activity detectable in the caecum of conventional chicks was inhibited by soybean trypsin inhibitor. However, the increased activity was not detectable in the small intestine and was, therefore, not due to pancreatic trypsin. 4. Attempts to demonstrate in vitro bacterial production of a trypsin-like enzyme were unsuccessful.