Animal Science, Department of
Department of Animal Science: Dissertations, Theses, and Student Research
First Advisor
James C. MacDonald
Date of this Version
12-2025
Document Type
Thesis
Citation
A thesis presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Master of Science
Major: Animal Science
Under the Supervision of Professor James C. MacDonald
Lincoln, Nebraska, December 2025
Abstract
Inconsistent availability or supply of distillers grains (DGS) can cause more variation in DGS inclusions throughout the feeding period. Two feedlot experiments evaluated the effects of varying inclusions of modified distillers grains plus solubles (MDGS) in feedlot diets. Beef steers (n = 400; initial BW = 287) were used in a 2 × 2 + 1 factorial experiment with treatments including: control with no MDGS compared to 2 inclusions (10% and 25%) of MDGS diet inclusions fed consistently or variably. No interactions were observed between MDGS consistency and inclusion for any performance or carcass characteristics (P > 0.10), so contrast statements were used to determine the linear and quadratic effects of inclusion for constant and variable treatments fitted through the control. Increasing the inclusion of MDGS from 0 to 25% of the diet and feeding it at the same diet inclusion consistently, linearly increased dry matter intake (DMI), average daily gain (ADG), hot carcass weight (HCW), and final body weight (P ≤ 0.03). Increasing the inclusion of MDGS from 0 to 25% with varying diet inclusion tended to increase ADG and HCW (P ≤ 0.09) but to a lesser degree than feeding at a constant inclusion. Steers (n = 229; initial BW = 426) were used in an individual animal feeding experiment with five treatments including: (1) corn control with no MDGS, (2) 25% MDGS constant inclusion, and 25% MDGS varying on a (3) daily, (4) weekly, or (5) monthly basis to assess the impact of frequency of changing MDGS inclusions. Feeding MDGS improved (P ≤ 0.06) ADG and HCW compared to the control. Cattle fed MDGS constantly had greater ADG compared to weekly variation. There was no difference between treatments for DMI (P = 0.42). Control cattle had the lowest G:F and cattle fed constant MDGS had the greatest G:F (P ≤ 0.05), with cattle fed the variable treatments being intermediate. There were no differences between treatments for carcass characteristics (P ≥ 0.12). There were no differences between treatments in number of bunk visits or time spent at the bunk each day (P ≥ 0.19). For the control, constant and daily treatments ruminal pH was 5.90, 6.13 and 6.10, respectively, with the corn control having the lowest pH (P < 0.04) compared to constant and daily. Results suggest that varying inclusions of MDGS had little impact in feedlot steers if fed the same amount on average over the feeding period. However, including MDGS in the diet was beneficial to just feeding corn.
Advisor: James C. MacDonald
Comments
Copyright 2025, Paige M. Madison. Used by permission