The Impact of Steam-flaked Rye Replacing Steam-flaked Corn on Performance and Carcass Characteristics of Yearling Steers and The Effect of Exogenous Megasphaera elsdenii Administration Techniques on Ruminal Fermentation and Blood Parameters in an Acidosis Challenge Model

Authors

Samantha K. Wagner, University of Nebraska-LincolnFollow

First Advisor

Galen E. Erickson

Second Advisor

James C. MacDonald

Date of this Version

7-2022

Comments

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 Professors Galen Erickson and James MacDonald. Lincoln, Nebraska: August 2022

Copyright © 2022 Samantha K. Wagner

Abstract

A feedlot study was conducted to evaluate the effects of replacing steam-flaked corn (SFC) with steam-flaked rye (SFR) in the diets of yearling steers (Exp. 1). A separate study was conducted to evaluate the effects of three different administration techniques of Megasphaera elsdenii NCIMB 41125 on rumen fermentation and blood parameters in an acidosis challenge model (Exp. 2). In Exp. 1, SFC was replaced with SFR to create four different treatments, each differing in the ratio of SFC:SFR. The four treatments were 0:100, 25:75, 50:50, and 100:0 SFR:SFC (as a percentage of the grain inclusion). Increasing inclusions of SFR resulted in linearly decreased final body weight, DMI, ADG, and HCW. As a result, feed efficiency was poorer as rye replaced corn. Carcass characteristics reflected lower gains with linear decreases in marbling score, longissimus muscle area, and backfat thickness. Based on dietary energy calculated from performance, SFR has approximately 92% the energy value of SFC. Steam-flaked rye can completely replace SFC in finishing diets. However, animal performance will decline which will result in lower HCW and carcass quality. Additionally, high levels of rye in the diet could create increased potential for acidosis or ergot toxicity. In Exp. 2, an acidosis challenge experiment was conducted in which 3 different administration techniques of Megasphaera elsdenii NCIMB 41125 (M.e.) were evaluated against a control. Treatments consisted of a control group which received no M.e. (CON), a group which received 1.0 × 10¹⁰ CFU of M.e. 4 days before to the acidosis challenge (COMM-4), a group which received 1.0 × 10¹⁰ CFU of M.e. one day before to the challenge (COMM), and a group which received 1.0 × 10¹¹ CFU of M.e. one day before to the challenge (10X). No treatment effects were found for DMI, rumination time, or average rumen pH. COMM-4 steers maintained higher minimum and maximum rumen pH. Differing trends were found for pH variance and magnitude through the duration of the experiment. Mixed results were found for volatile fatty acid concentrations, with COMM having the highest total VFA concentration, CON and 10X the lowest, and COMM-4 intermediate. The COMM-4 treatment also had greater blood lactate and decreased blood pH during the recovery period. During the challenge period, treated groups had higher monocyte counts and the 10X group showed higher levels of TNF-α compared to all other treatments. In conclusion, treating steers with M.e. four days before to an acidosis event has the potential to maintain rumen pH without affecting DMI or rumination time.

Advisors: Galen E. Erickson and James C. MacDonald