Author ORCID Identifier

https://orcid.org/0009-0004-6546-5877

Semester

Spring

Date of Graduation

2026

Document Type

Dissertation

Degree Type

PhD

College

Davis College of Agriculture, Natural Resources and Design

Department

Animal and Nutritional Sciences

Committee Chair

Joseph Moritz

Committee Member

Janet Tou

Committee Member

Cangliang Shen

Committee Member

Jessica Blythe

Committee Member

Staci Cantley

Abstract

Applied poultry nutrition and feed manufacture science can be described as a “three-legged stool” supported by pellet quality, feed hygienics, and nutrient availability, where imbalance in any one component can compromise overall bird performance. The research presented herein primarily addresses feed hygienics and nutrient availability, with pellet quality serving as an underlying theme, to better understand how processing conditions and dietary formulation influence performance and nutrient utilization.

In Chapter 2, the objective of this study was to evaluate the effects of hygienizer retention time on bacterial reduction during feed manufacture using Enterococcus faecium as a Salmonella surrogate. Pellet mill motor load and pellet durability were not affected by treatment (P>0.05), while hygienizer temperature, hot pellet temperature, and moisture differed (P< 0.05). No differences in bacterial enumeration were observed among inoculated pelleted treatments (P>0.05). Pelleting, regardless of treatment, reduced bacterial populations by approximately 1.46–1.65 log10 CFU/g and an average matched pairs reduction of 1.53 log10 CFU/g. Because these reductions were lower than expected, a follow-up lab-based model was utilized to evaluate the effects of 3 bacterial Sources, 2 enumeration media, and 5 thermal exposure times on bacterial inactivation. Thermal exposure increased bacterial reduction (P< 0.0001), with reductions increasing from 3.60 to 4.39 log10 CFU/g between 0 and 3 min before plateauing. Bacterial source (P< 0.0001) and enumeration media (P< 0.0001) influenced recovery, with the NaL-resistant source exhibiting greater thermal tolerance and selective media recovering more heat-injured cells, indicating that methodological factors contributed to variation in observed bacterial reduction.

In Chapter 3, the purpose of this study was to evaluate the effects of varying branched-chain amino acid ratios and tryptophan inclusions on turkey poult performance, litter moisture, and plasma serotonin in a 42-day grow out. During d0–21, birds fed the positive control and HCG + Val + Ile + Trp diets demonstrated the greatest feed intake and live weight gain (P< 0.05). By d0–28, the HCG + All diet resulted in the lowest feed conversion ratio, although differences between PC and HCG treatments were no longer significant for live weight gain and FCR (P< 0.05). By d42, the HCG + All diet maintained similar or improved performance relative to the PC. Litter moisture differed among treatments at d42 (P=0.0139), with the PC yielding the highest moisture, and plasma serotonin trended toward significance (P=0.0980), with numerically greater values observed in the PC. These results imply that early performance is negatively impacted by amino acid imbalances. However, birds demonstrate compensatory growth with age. Supplementation of Val, Ile, and Trp can restore performance in high Leu diets.

In Chapter 4, the objective of this study was to evaluate corn and soybean meal-based starter diets that exclude inorganic phosphorus or contain low non-phytate phosphorus with

phytase supplementation on broiler performance, bone mineralization, and dicalcium phosphate equivalency. Diets containing 0.13% and 0.22% non-phytate phosphorus decreased live weight gain, feed intake, and tibia mineralization relative to the positive control (P< 0.05). Inclusion of a commercially available phytase at 1,500 FTU/kg increased live weight gain, individual body weight, feed intake, and tibia mineralization compared to the 0.22% nPP diet or diets containing phytase B or C (P< 0.05), Mortality was less than two birds per pen and was not affected by treatment. Phytase supplementation did not overcome nutrient deficiencies in diets completely devoid of inorganic phosphorus, and responses varied among phytase products, indicating differences in efficacy.

In Chapter 5, the objective of this study was to evaluate the effects of increasing dietary calcium in broiler starter diets that omit dicalcium phosphate, with or without phytase, across two levels of phytate-P. As dietary Ca:nPP ratios widened, live weight gain and feed intake decreased, while feed conversion ratio and mortality increased relative to the positive control (P< 0.05). Phytase inclusion at 1,500 FTU/kg restored performance to that of the positive control when calcium was provided at 0.58% or greater in corn/soybean meal + wheat middlings diets and 0.70–0.83% in corn/soybean meal diets. These results indicate that successful removal of inorganic phosphorus is dependent on maintaining appropriate Ca:nPP ratios in conjunction with effective phytase inclusion and dietary phytate-P.

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