| dc.description.abstract | The objective of this research was to quantify improvements in nutrient
digestibility and performance using multiple exogenous enzymes which target different
substrates in diets varying in nutrient density. Experiment one consisted of three control
diets varying in dietary energy with the supplementation of xylanase at two inclusion
rates. Reducing the dietary energy level negatively influenced feed conversion ratio
(FCR) and decreased the fat pad weight of broilers in the reduced energy diet compared
to the positive control. The inclusion of xylanase reduced FCR throughout the trial
compared to the control. These results demonstrate the effectiveness of xylanase
inclusion in reduced energy diets to improve FCR of broilers.
Experiment two evaluated the inclusion of a cocktail NSPase and β-mannanase,
separately or intermittently, on broiler growth performance and processing. Broiler
performance was improved with the inclusion of a cocktail NSPase and β-mannanase
throughout the experiment. When evaluating weight gain from d 22 to 47, the
intermittent application of cocktail NSPase and β-mannanase improved weight gain
compared to the positive control diet. The results of this experiment confirm the ability
of exogenous enzymes to improve the nutritive worth of feed ingredients by enzymatic
degradation.
Experiment three determined the impact of corn source on broiler performance
and nutrient digestibility with or without the inclusion of xylanase. The variability of
nutrient profile between corn sources influenced body weight, FCR, and nutrient digestibility throughout the trial. Xylanase inclusion improved FCR in the finisher phase
suggesting that the length of time feeding enzymes may be impactful to the final
outcome of performance. The results of this experiment indicate the importance of rapid
and accurate evaluation of corn nutrient content to maximize observed growth
performance.
Experiment four evaluated the effects of calcium (Ca) and phosphorus (P) level
in a diet containing super-dose (> 3X dose) levels of phytase on male broiler
performance and breast meat yield. Calcium and P level influenced broiler performance,
tibia ash percent, fecal mineral content, and litter mineral content. These data illustrate
the importance of utilizing the correct Ca and P matrix value in diets containing phytase.
This research program outlines the importance of adequate understanding of nutritional
value of raw ingredients for accurate formulation when utilizing exogenous enzymes. | en |
