Date of Graduation


Document Type


Degree Type



Davis College of Agriculture, Natural Resources and Design


Animal and Nutritional Sciences

Committee Chair

Joseph S Moritz

Committee Co-Chair

Eugene E Felton

Committee Member

Janet C Tou


Applied research conducted at universities is essential for further advancements in poultry science and ultimately the commercial poultry industry. One important area of applied nutrition research is examining production methods associated with the important feed additive/enzyme phytase. Exogenous phytase inclusion in poultry diets has consistently been associated with decreased diet cost, increased broiler performance, and reduction in negative environmental impact. However, thermal stability of commercial phytases are variable. Strategies for production of phytases that ultimately maintain activity after being subjected to the pelleting process is essential. Phytase manufacturers have modified production methods in an effort to maximize phytase thermal stability and efficiency. The first study (Chapter 2) describes two experiments that assessed the effects of particle size distribution and bulk density of the carbohydrate-lipid coating on phytase retention and broiler performance. This study demonstrated that phytase manufacturers should utilize large particle size and a low bulk density to maintain the greatest enzyme thermal stability. This study also demonstrated that phytase manufacturers should utilize a broad range particle size distribution with a low bulk density to create the most efficacious phytase in regards to phosphorus digestibility and broiler performance. These studies further demonstrated the importance of conducting a combination of in vivo and in vitro experiments to truly depict phytases efficacy. Another important area of research is assessing improvements in feed form on broiler performance. However, university research often utilizes small floor pens and feed pans that provide greater feeder space access than encountered in typical commercial production. Feeder space access may be an important variable that influences research results, especially coupled with differing compositions of feed that broilers receive in the feed pan. The second study (Chapter 3) describes a 2 x 2 factorial using the main effects: high or low feed composition (70% vs 40%) and increased or industry feeder space access (5.9 cm/bird vs 1.2 cm/bird) to determine effects on broiler performance. This study showed that presenting a high feed composition resulted in improved broiler performance. Feeder space access also influenced broiler performance and interacted with the feed composition main effect. This suggests future research should consider feeder space access so that results are most relevant to the commercial broiler industry.