Semester

Fall

Date of Graduation

2023

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Animal and Nutritional Sciences

Committee Chair

Joseph S. Moritz

Committee Member

Janet Tou

Committee Member

Ibukun M. Ogunade

Committee Member

Jacek Jaczynski

Abstract

In Chapter 2, an experiment was conducted to evaluate the effect of different mixer types (MTY) and mix times (MTI) on mix uniformity (MU). A 2 (mix time) x 3 (mixer type) factorial was utilized in this experiment to create six treatments, each mixed in three randomized complete blocks. Mix times were designated adequate or inadequate, were based on the manufacturers’ recommendation, and varied based on the mixer utilized. The mixer types utilized included a vertical mixer, horizontal mixer, and transfer mixing system. The transfer mixing system can be described as a batch-to-mix system that simulates the process of conveying batched feed to a mixing location. Chloride ions (Cl-) via salt, crystalline DL-Methionine (Free Met), and crystalline L-Lysine-HCL (Free Lys) were utilized as coefficient of variation (CV) markers, with Cl- being used in a corn-salt (CS) ration and the Free Met and Free Lys being used in a complete diet (CD). An interaction between MTY and MTI affected Free Met CV (P = 0.005). The horizontal mixer and transfer mixing system did not demonstrate changes in the Free Met CV compared to the vertical mixer when MTI was manipulated. The authors hypothesize that additional mixing during load-out and added conveyance caused this interaction. The transfer mixing system resulted in the lowest Free Lys CV (P = 0.017); however, no treatment provided an industry-acceptable MU. In conclusion, Free Lys may not be an appropriate marker for MU, Free Met may be an appropriate marker for MU in complete diets, and the transfer mixing system may contribute to an acceptable MU.

In Chapter 3, an experiment was conducted to evaluate the influence of pellet die thickness (PDT) and Azomite® (AZM) on feed manufacture. A 2 (AZM) x 3 (PDT) factorial was utilized in this experiment to create a total of six treatments, each manufactured in every run order position in a Latin Square Design. Azomite inclusion rate was either 0.0% (control) or 0.25%, and 32mm, 38mm, and 45mm PDTs were utilized in their appropriate treatments. The pellet diameter was held to a constant of 4.5mm. The objective of this study was to evaluate the effect of AZM and PDT on pellet production rate (PPR), pellet durability index (PDI), and hot pellet temperature (HPT) in corn, soybean meal, and dried distillers grains with solubles-based poultry diets, manufactured under a constant motor load. The inclusion of AZM increased overall PPR by 7.9% (P < 0.001) and decreased overall PDI by 1.6 percentage points (P < 0.001). As PDT increased from 32mm to the average of the 38 and 45mm treatments, PPR decreased by 28.5% (P < 0.001) and increased PDI by 10.1 percentage points (P < 0.001). A main effect interaction of AZM and PDT was recognized to influence HPT (P < 0.007), however, no difference was observed for the 45mm PDT when AZM was included. Linear contrasts showed that PPR increased by 5.0, 7.9, and 11.8% when comparing AZM treatments to their respective controls (All PDT; P < 0.001). The authors of this experiment concluded that AZM increased PPR across PDT and decreased PDI, albeit to the extent that would likely not affect broiler performance.

In Chapter 4, a follow-up experiment to the previous was conducted to evaluate the influence of PDT and AZM inclusion rate on broiler performance and apparent ileal amino acid digestibility (AIAAD). A 2 (AZM) x 2 (PDT) factorial was utilized in this experiment to create a total of four treatments. The dietary treatments were sourced from the previous AZM experiment, and only the treatments utilizing the 32 and 45mm PDT were utilized. All feed was reground and slightly reformulated to reduce the confounding bias of PDI and to ensure an acceptable nutritional density. Ten randomized complete blocks of raised wire cages were utilized with each pen housing ten Ross 308 broilers. The objective of the study was to determine the effect of pelleted feed using AZM (0.0 or 0.25%) and PDT (32 or 45mm; using a constant die diameter of 4.5mm) on Ross 308 male broiler feed intake, live weight gain, feed conversion ratio, and AIAAD from 0 to 21 days of age. Live performance did not differ due to an interaction or independent main effects (P > 0.05). However, AIAAD was influenced by AZM and PDT interactions (P < 0.05). The amino acids Ala, Asp, Glu, Gly, Ile, Lys, Met, Pro, Thr, and Val demonstrated increased digestibility with the 45mm Control treatment. This treatment also produced the highest numerical HPT in the feed manufacture experiment. It was hypothesized that the digestibility resulted from increased frictional heat that deactivated trypsin and chymotrypsin inhibitors or degraded ingredient cell wall structure. While both inhibitors were determined to be present using SDS-PAGE and chemiluminescent detection, quantitative analysis showed no practically influential concentrations of either inhibitor or a decrease large enough to explain the increased AIAAD. The authors, therefore, speculate that the increase in AIAAD of various amino acids was due to the breakdown of the aleurone layer cell walls of the corn kernels caused by increased frictional heat exposure vis the 45mm PDT and the absence of AZM.

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