Date of Graduation


Document Type


Degree Type



Davis College of Agriculture, Natural Resources and Design


Agricultural and Resource Economics

Committee Chair

Joseph Moritz

Committee Co-Chair

Ida Holaskova

Committee Member

Kenneth Ryan

Committee Member

Robert L Taylor

Committee Member

Janet Tou


The objective of the first study was to assess the effect of variations of feed form and dietary caloric density on production and immunity parameters in broilers reared on clean shavings and built-up litter. Treatments were arranged in a 2 x 2 factorial randomized block design within a split plot. Whole plot treatments considered one room (11 x 7.32m) of either clean shavings or built-up litter; divided into 16 treatment replications of either standard (30%) or improved (80% feed form), and 16 replications of either commercial or increased (+110 kcal/kg) dietary caloric density comprising the 2 x 2 factorial arrangement. Broilers consuming an improved feed form demonstrated an improved feed intake (FI), live weight gain (LWG), feed conversion ratio (FCR), breast weight and breast yield (p < 0.05). Providing an improved feed form demonstrated an increased concentration in IgG (p < 0.05). An environment x energy interaction (p < 0.05) demonstrated increased concentration of IgG in broilers fed a commercial energy reared in a built-up litter environment, whereas broilers maintained a similar IgG concentration when fed an increased energy regardless of environment. Linear contrasts demonstrated that broilers provided improved feed form at commercial energy increased FI and LWG (p ≤ 0.05), while maintaining FCR (p > 0.05) compared to broilers provided standard feed form at increased energy regardless of environment. These data suggest feed form improvements may partition energy towards growth more than feeding an increased energy diet.;The objective of the second study was to assess the effect and potential for interaction of corn/soy diets containing variable Ca/tP ratios and phytase inclusions on straight-run broiler performance and mineral deposition. A positive control was compared to 12 treatment combinations comprised of a 4 x 3 factorial arranged in a randomized complete block design. Main effects consisted of four Ca/tP ratios (1.0, 1.2, 1.4, and 1.6) and three inclusions of phytase (low ≈ 1,000, medium ≈ 2,000, and high ≈ 3,000 FTU/kg). All diets were steam conditioned at 82°C for 10s and extruded through a 4.7 x 38 mm pellet die. Diets were crumbled via roller mill for starter (d 1-14) and grower (14-28) growth phases and left as intact pellets for the finisher phase (28-42). Straight-run Hubbard x Cobb 1-day-old broiler chicks were obtained from a commercial hatchery and randomly assigned to floor pens (0.69 x 2.4 m) at a density of 0.06 m2/bird (23 birds/pen) with feeder access space of 1.2 cm/bird. Seven replicate pens of broilers were fed one of 13 dietary treatments for 42 days. Tibia extraction and total GI tract digesta were collected on d 28. Higher phytase inclusions increased LWG (p = 0.0166) and decreased FCR (p = 0.0016) in the starter growth phase. Increasing Ca/tP decreased LWG (p = 0.0005) in the grower phase. High phytase inclusion demonstrated a decreased LWG (p = 0.0428) in the finisher phase. Phytase inclusion and Ca/tP ratio interacted for starter FI (p < 0.05) and demonstrated a trend of interacting for finisher and overall FI (p = 0.1). In general, higher feed intakes were associated with high inclusions of phytase in diets with a 1.4 Ca/tP ratio. Overall growth performance was not significantly affected by treatment (p > 0.05). Mineral digestibility was improved when Ca/tP decreased (p < 0.05) and phytase inclusion increased (p < 0.05). Bone mineralization measures in general showed improvement at a Ca/tP ratio higher than 1.0 (p <0.05). Based on these data; broiler performance and mineral deposition was optimized for 1.2 and 1.4 Ca/tP ratio and phytase inclusions above 1,000 FTU/kg.