A series of experiments was conducted to evaluate the effects of amylase supplementation upon the endogenous amylase levels and growth performance of male turkey poults. [In the first experiment, a multi-enzyme supplement containing amylase and an additional protease supplement were added to diets of low (24%) and high (28%) protein content. Enzyme supplements Significantly improved performance of birds on the low, but not on the high protein diet. Even with the improvement from enzyme addition, the performance of poults fed the low protein diet was not equal to poults fed the high protein diet. The second experiment was designed to evaluate the effect of varying levels of amylase and xylanase on bird performance, and to determine optimal level of enzyme inclusion in the basal corn-soybean meal diet. Feed utilization or growth of birds did not differ between the amylase diets, however 200 units of amylase per kilogram of feed produced numerically optimal growth and feed efficiency values. Xylanase inclusion greater than 160 units per kilogram of feed appeared to be detrimental to bird growth and feed efficiency. In the third experiment, endogenous amylase levels were measured to determine if supplemental amylase produced a quantitative, qualitative, or inhibitory effect upon the endogenous amylase activity. Amylase supplementation was found to be additive to the endogenous levels and did not inhibit endogenous activity. Amylase supplemented diets decreased body weight and feed efficiency loss due to weighing and handling stress on the birds when compared to the control and xylanase diets. Villi lengths within the jejunal and ileal sections of the small intestine were longer during the first three weeks for amylase supplemented birds when compared to intestinal villi of either the control or xylanase fed poults. The fourth experiment was conducted to compare the effect on growth and feed utilization of the serial addition of various enzyme preparations to corn-soybean poult diets. In retrospect, due to the serial application of the supplements, assessment of the benefits of a given supplement within a composite application was futile. Amylase, however, was present within the composite supplements fed to poults with the highest growth performance values. These experiments suggest that the addition of amylase to conventional corn-soybean meal turkey poult starter diets can be effective in improving growth and feed utilization during the first few weeks. The addition of amylase supplements to basal diets did not inhibit the poult endogenous amylase activity levels and were associated with increased intestinal villus length corresponding to increased utilization and absorption of nutrients. Xylanase appeared to be a detrimental enzyme additive to corn-soybean meal diets fed to male poults. / Ph. D.