Effect of Phytase and Glucanase, Alone or in Combination, on Nutritive Value of Corn and Soybean Meal Fed to Broilers
Type of DegreeDissertation
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In order to efficiently use exogenous enzymes, the effects of these products on nutrient availability must be determined. A series of experiments were designed to evaluate a phytase and a glucanase supplemented to corn-soybean meal diets. The first two experiments were bioassays, using diets with either adequate or low aP fed to broilers between 5 and 10 d of age. AME, ileal digestible energy (IDE), productive energy (PE) and digestibility of minerals and CP were determined. Glucanase supplementation increased IDE and AME in adequate aP diets, but not PE. Phosphorus, Ca and CP digestibility were improved by phytase, but there was no effect of this enzyme on energy parameters. An experiment designed to investigate the effects of phytase and glucanase on IDE of corn and soybean meal separately, and at various ages was performed. Broiler chicks were fed either corn or soybean meal with or without enzyme supplementation, from 7 to 9, 14 to 16, or 21 to 23 days. Glucanase improved the IDE of both feedsuffs by approximately 100 kcal/kg at all three ages. Phytase did not affect IDE at any age. The location and extent of phytate degradation, and the effects of phytase and day length were investigated. Broilers were fed complete diets with or without phytase, and were exposed to either 12 or 24 hours of light per day. The experiment was performed between 20 and 24 d of age. The degree of phytate degradation was determined through analysis of digesta and excreta samples for the products of degradation (IP5 through IP2). Degradation occurred primarily in the crop, gizzard and proventriculus. Phytase decreased IP6 and increased IP5 concentrations. Shorter day length generally increased phytate degradation. Phytase supplementation increased ileal IP6 digestibility from 41 to 60%. A final experiment was designed to confirm the results seen in previous experiments in a practical trail. A positive control (PC) was formulated to meet all nutrient requirements. A negative control was formulated by reducing the energy, aP and Ca level in the positive control by 90 kcal/kg, 0.15% and 0.20% respectively. Phytase, glucanase and both enzymes together were supplemented to the NC to create 5 diets. Phytase supplementation improved the performance of birds fed the NC to the level of those fed the PC diets for all response variables. Glucanase supplementation failed to improve the NC diet for any response variable. These experiments show that the phytase used can replace 0.15% aP and 0.20% Ca in corn soybean meal diets. While there was no energy response in the bioassay experiments, the practical experiment suggests that there is an energetic response to phytase supplementation. Glucanase supplementation did not result in an energy response in practical situations.