| dc.description.abstract | Two studies were performed to evaluate the efficacy of supplementing exogenous enzyme combinations on broiler growth performance in reduced nutrient density corn-soybean meal diets. In experiment 1, 3,200 Cobb 500 broilers were allocated to 5 treatments with 16 replicates for 39 days. The experiment consisted of a nutritionally complete positive control, AME reduced negative control (NC), NC + Non-starch polysaccharide degrading enzyme (NSPase) containing xylanase, β-glucanase, α-galactosidase, NC + an enzyme combination of xylanase, amylase, protease (XAP), and NC + NSPase + XAP. Apparent metabolizable energy in the NC was reduced by 55 kcal/kg in the starter phase and 88 kcal/kg in the finisher and withdrawal phases. Energy reduction in the NC significantly decreased average BW and significantly increased FCR through the starter and finisher phase. Non-starch polysaccharide degrading enzyme inclusion increased average BW significantly compared to the negative control at levels similar to that of the positive control during the starter and finisher phases. Non-starch polysaccharide degrading enzyme significantly reduced FCR compared to the NC at levels that were similar to the positive control. Inclusion of XAP resulted in BW similar to the PC at d 14 and 27, and reduced (P<0.05) FCR from d 1 to 27. The combined inclusion of NSPase + XAP resulted in no further benefit beyond individual inclusion of each enzyme combination. In experiment 2, 2,590 Cobb 500 broilers were allocated to 7 treatments with 10 replicates for 41 d. Treatments consisted of a nutritionally complete reference diet, and 6 AME reduced (-88 kcal/kg) treatments composing a 2 X 3 factorial of phytase and XAP inclusion. Phytase was included at 600 (low) and 1,200 (high) FTU/kg, with XAP included at 1,200 (low), 1,800 (medium), and 2,400 (high) XU/kg. High phytase x low XAP and high phytase x medium XAP both resulted in similar cumulative FCR compared to the reference diet. Factorial analysis indicated high phytase compared to low phytase significantly reduced starter FCR and elevated finisher mortality. During the starter phase, medium XAP inclusion resulted in a significantly lower rate of feed consumption compared to the low XAP. Inclusion of medium XAP significantly reduced cumulative FCR from d 15 to 41 compared to low level XAP. These data indicate that supplementation of multiple enzyme preparation into a diet can influence growth performance; however, combinations of enzyme preparations similar in mode of action do not result in performance levels beyond that of individual preparation inclusion. | en |
