Date of Graduation


Document Type


Degree Type



Davis College of Agriculture, Natural Resources and Design


Agricultural and Resource Economics

Committee Chair

Joseph S Moritz

Committee Co-Chair

Omar Gutierrez

Committee Member

Jacek Jaczynski

Committee Member

Michael Lilburn

Committee Member

Robert L Taylor

Committee Member

Jennifer Weidhaas


Animal well-being, evolving feed manufacturing regulatory programs, and consumer perception drive the continued need to provide safe feed to animals. Considering the performance benefits associated with feeding pelleted feed, the concepts of hygienic feed production and production of highly durable pellets may interact to benefit the broiler chicken. In addition to hygienic and physical attributes, poultry nutrition may be enhanced by cereal grains expressing enzymatic activity. These additives may provide additional opportunities to support dietary phosphorus (P) requirements in growing broilers, further contributing to improved animal welfare conditions in an economically favorable manner. In order to study the effects of these unique aspects of feed and poultry production, multiple experiments were designed.;Initially, two experiments were conducted, using both short-term (ST) and long-term (LT) steam conditioning, to determine the effects of antimicrobial inclusion and conditioning temperature variations on feed manufacturing metrics (EXP1) and the mitigation of a Salmonella surrogate (EXP2). A split-plot design was utilized where ST (10s) or LT (60s) steam conditioning served as whole plot units. Each whole plot unit contained both a 2 x 3 (EXP1) and a 2 x 4 (EXP2) factorial arrangement of treatments varying in antimicrobial inclusion (With or Without) and degree of thermal processing ((Unprocessed Mash), 71, 82, 88°C). In EXP1, conditioning time and antimicrobial inclusion interacted (P=0.03) by decreasing pellet durability when antimicrobial was included to diets subjected to ST conditioning. Durability detriments were not apparent when LT conditioning was utilized. In EXP2, conditioning time, antimicrobial inclusion, and degree of thermal processing interacted (P<0.0001), decreasing mitigation when ST conditioning was applied to surrogate inoculated feed at 71°C, relative to higher conditioning temperatures and when ST and LT conditioning was applied to antimicrobial treated feed.;Then, two additional experiments were conducted to study variables common to phytase enzyme optimization when supplied to P deficient diets. The objectives of the third experiment were to describe the effects of Corn-Expressed Phytase (CEP) varying in particle size (1.5, 2.0, or 2.5mm), concentration (500 or 3,000 FTU/kg), and coating (with or without) on 38 d broiler performance and tibia mineralization. Treatments were arranged in a 3 x 2 x 2 factorial in a randomized complete block design (RCBD). Commercial phytase, supplemented at 500 or 3,000 FTU/kg, as well as positive control (PC) and negative control (NC) diets were also fed. Broilers fed CEP at 3,000 FTU/kg demonstrated improved live weight gain (LWG), feed conversion ratio (FCR), and bone mineralization compared to broilers fed CEP at 500 FTU/kg (P<0.05). Broilers fed CEP of 2.0mm had improved FCR compared to broilers fed CEP of 2.5mm (P<0.05). Coating did not affect broiler performance or tibia mineralization. The efficacy of CEP was comparable to the positive control diet and commercial phytase product when particle size and concentration was optimized.;Finally, the objective of the fourth experiment were to describe the effects of various CEP product coatings and concentrations on 38 d broiler performance and bone mineralization. Treatments were arranged in a 5 x 2 factorial in a RCBD that varied in proprietary CEP coating technique (Product 1- Product 5) and concentration (500 or 1,500 FTU/kg). PC and NC diets, varying in non-phytate P (0.46% vs 0.25% respectively), were also fed. Product coating affected FI and LWG, decreasing consumption and gains when broilers were provided either Product 1 or Product 4 (P<0.05). Broilers fed CEP at 1,500 FTU/kg increased FI by 259 g per bird (P<0.0001), LWG by 240 g per bird (P<0.0001), and all bone mineralization metrics (P<0.05), relative to those fed CEP at 500 FTU/kg. Multiple comparison analyses show PC fed birds improved performance above NC fed birds (P<0.05). Within the parameters of these four experiments, optimizing CEP particle size, dietary concentrations, and proprietary coating techniques may liberate bound P in the diet, improving broiler performance and bone mineralization. Furthermore, both ST and LT steam conditioning display the potential to mitigate bacteria in feed. However, degree of bacteria mitigation and pellet quality are dependent on specific manufacturing and additive strategies.