The effect of adding exogenous protease on the activity of endogenous enzymes in the digestive tract of animals is affected by multiple factors such as animals (type, physiological stage, age), feeding environment, diet type, etc. The mechanism is very complicated. Most studies have shown that the addition of exogenous proteases can stimulate or promote the secretion of endogenous enzymes in animals, but there are also individual studies that show that the addition of low doses of exogenous enzymes promotes the secretion of endogenous enzymes in the digestive tract of animals, while high doses Exogenous enzymes have a certain inhibitory effect on the secretion of endogenous enzymes in the digestive tract of animals. Some studies (Inborr, 1990) believe that feed enzyme preparations are generally fermented by microorganisms, and have no homology with endogenous enzymes secreted by the digestive tract of animals, and so-called "feedback inhibition" is unlikely; There is a complementary relationship between the restriction site of the source digestive enzyme and the restriction site of the endogenous digestive enzyme, which not only does not inhibit, but also has a synergistic effect.