Date of Graduation


Document Type


Degree Type



Davis College of Agriculture, Natural Resources and Design


Animal and Nutritional Sciences

Committee Chair

Joseph Moritz

Committee Member

Jacek Jaczynski

Committee Member

K. Marie Krause


Modern broiler production strives to make modest improvements regarding broiler performance. This remains a goal as global population increases thusly increasing the quantity of an affordable, high quality source of protein. In recent years, an added stressor to achieving prior goals is mostly related to consciousness of environmental and consumer health. For decades, integrators have utilized minimal amounts of antibiotics as a barrier to most pathogens affecting the microbiome of a broiler’s gastrointestinal tract. Regulatory efforts have now prohibited most of previous sub-therapeutic medicine and started an in-depth scope of broiler gut health and interaction with antibiotic alternatives. In an effort to provide beneficial bacteria in a challenged environment, broilers were fed Direct-Fed Microbials (DFM), notably Bacillus subtilis, to investigate performance improvements. Diets were formulated to meet bird requirements during specific age periods. 2,280 male Ross x Ross 708 broilers were placed on study for 42 days to evaluate live performance. Pens of 23 broilers were randomly assigned one of four dietary treatments; a control diet, and 3 diets compromised of the control and an additional top dressed DFM. A natural challenge was manifested by a combination of built-up litter and a weekly water spray to facilitate bacterial growth. Additionally, the diet was nutritionally limited. The results revealed that dietary treatments performed the same for most measurements. Live weight gain decreased in diets containing DFM2 or DFM3. Overall, broilers performed below industry expectations in each performance variable, suggesting the additive effect of nutritional deficit, floor conditions, and heat stress may have hindered opportunity for DFMs to perform or provide enough stimulus to generate expected results.

Additionally, transgenic grains were implemented into broiler diets to identify ability to liberate Ca and P by expressing phytase at two different concentrations. Different expressions resulted in volume discrepancies. Distribution throughout a mixer was of interest to identify potential for minimizing dietary inclusion thusly total cost. Phytase has long been utilized to combat P excretion in the poultry industry related to environmental concerns. Grain-expressed enzymes allow for a direct 1:1 replacement for the host grain. Adding exogenous enzymes without diluting dietary nutrients will be another means of improving performance by maximizing nutrient utilization. 2,304 male Ross x Ross 708 broilers were obtained and placed in pens of 24. A dietary factorial treatment structure was utilized for two corn-expressed phytase products at three doses. Additionally, a positive and negative control were used. Birds were selected randomly at day 21(n=5) and day 42(n=3), to be euthanized for tibia excision. Tibiae were collected, ashed and bone mineralization was determined to quantify liberation of additional P/Ca. Live performance was also measured. Results showed that a lower concentrated grain enzyme requires more volume and has more opportunity to distribute evenly during batching of a diet. This is reinforced by performance results that yield improved LWG for a product that requires more volume for a target dose.