Semester

Spring

Date of Graduation

2022

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 Co-Chair

Thomas Basden

Committee Member

Thomas Basden

Committee Member

Mark Lemons

Committee Member

Janet Tou

Committee Member

Amy Welsh

Abstract

Experiments were conducted to investigate the effects of varying feed ingredients and heating systems on boiler performance metrics. Chapter Two investigated the effects of two corn-expressed phytases, differing in enzyme concentration within the grain (3,000 or 9,677 FTU/g), on broiler performance and tibia mineralization, when used as a component in pelleted feed. Dietary treatments included a positive control (PC), with industry-recommended levels of calcium and phosphorous, and a negative control (NC), lower in calcium and non-phytate phosphorous. Six diets containing corn-expressed phytase at high or low grain concentrations, formulated to 3,000, 6,000, or 9,000 FTU/kg, were created using the NC. Diets were conditioned at 70°C for 15s. Descriptive enzyme recovery post-pelleting (58-360%) and mixer coefficient of variation based on enzyme activity (8-24%) demonstrated variability with the phytase assay and did not show trends across treatment main effects. Diets were fed to Hubbard x Ross 708 (n=1,632) male broilers for 39d. On d21, five birds/pen were euthanized and tibiae were excised to determine tibia mineralization. Broilers fed the NC had increased d0-39 feed conversion ratio (FCR) compared to all other treatments (PPP

Chapter Three examined the use of a muramidase in broiler diets. Muramidase breaks down peptidoglycans from bacterial cell debris in the gastrointestinal tract, improving nutrient utilization. The first objective of Chapter Three was to evaluate the effect of muramidase, conditioning temperature, and conditioning time on feed manufacture. The second objective was to evaluate muramidase activity and broiler performance when diets were conditioned at various temperatures and times. Experiment 1 consisted of a nutrient adequate, corn and soybean meal based diet (Basal), and the Basal+muramidase at 100K LSU(F)/kg diet. Both diet formulations were conditioned at 77, 82, or 88°C for 30 or 60 s. Feed manufacture was replicated across three days of manufacture. Experiment 2 utilized the Basal conditioned at 88°C for 30 and 60 s and the Basal+muramidase conditioned at 77, 82, or 88°C for 30 or 60 s. Crumbled diets were fed to 12 replications of ten male Hubbard x Ross 708 broiler chicks for 21 d. Increasing conditioning temperature decreased pellet mill motor load and increased hot pellet temperature (HPT) and pellet durability in Experiment 1 (PPExperiment 2 found that the inclusion of muramidase decreased FCR and increased live weight gain (LWG) for 30 s (PP>0.05). Muramidase improved performance post 30 s conditioning, regardless of conditioning temperature, compared to a nutrient adequate Basal.

The objective of Chapter Four was to investigate the effects of two feed additives (antibiotic and muramidase) provided to broilers reared using two heating systems (external combustion wood boiler heat exchanger or radiant propane brooders), on broiler performance, foot pad quality, and immune status. Two identical experiments were completed, using two identical rooms heated with either radiant propane brooders or a wood boiler heat exchanger. 1,472 Ross-308-AP straight-run broiler chicks were utilized for each experiment, for 35 days. Each room contained 32 floor pens. One of four dietary treatments (PC, NC (15% reduction in digestible amino acids), NC + antibiotic, NC + muramidase) were randomly assigned to each pen within a block. A block consisted of four adjacent floor pens; eight blocks were utilized for each room per experiment. The use of a wood boiler heat exchanger reduced d21 litter moisture (P=0.1013), d23 serum IL-6 (PP=0.0112), relative to radiant propane brooders. Diet influenced 0-35d LWG and FCR. The PC had the highest LWG and lowest FCR, NC had the lowest LWG and highest FCR, with antibiotic and muramidase being intermediate (PP<0.05). Heating system did not affect overall performance (P>0.05). The wood boiler heat exchanger and both tested feed additives had positive influences on broiler production.

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