Date of Award:

5-2015

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Animal, Dairy, and Veterinary Sciences

Advisor/Chair:

Jong-Su Eun

Abstract

In the beef cattle industry, sustainable beef production is a primary focus, as it has direct effects on environmental stewardship, farm profitability, and public concerns. Research has been and is continually being conducted to evaluate alternative forages such as Brown Midrib Corn Silage (BMRCS) as a major component in growing beef cattle diets, to improve animal performance, ruminal fermentation, and economic returns. The objective of this study was to determine growth performance, ruminal fermentation characteristics, and economic returns of growing beef steers when fed a brown midrib corn silage-based TMR (BMRT) compared with a conventional corn silage-based TMR (CCST). This growing beef study was performed in a completely randomized design with 24 Angus crossbred steers (initial body weight (BW) = 258 ± 23.2 kg) to test 2 treatments: CCST vs. BMRT. All animals were placed in individual pens, and 12 animals allocated to each treatment (n = 12). All steers were adapted to the CCST for a 2-wk period prior to start of the trial. The CCST contained 48.1% CCS whereas the BMRT consisted of 49.0% BMRCS on a dry matter (DM) basis. All steers were fed once per day, and feed bunks assesed each afternoon and prior to morning feeding, which was used to determine the amount of feed to deliver to each pen the following day. The experiment lasted 84 d. For all steers, BW and ruminal fermentation characteristics were measured on wk 4, 8, and 12. Intake of DM averaged 9.54 kg/d across the treatments and was similar between the treatments. Steers fed the BMRT tended to increase average daily gain (ADG) compared to those fed the CCST (1.54 vs. 1.42 kg/d; P = 0.09). In addition, feeding the BMRT tended to increase G:F compared with the CCST (0.165 vs. 0.146; P = 0.07). Feeding the BMRT decreased ruminal pH (6.42 vs. 6.67; P < 0.01), whereas it increased total VFA concentration (P = 0.01) compared with the CCST. Feeding the BMRT decreased molar proportion of acetate (P < 0.01), but increased propionate proportion (P = 0.01), resulting in decreased acetate-to-propionate ratio compared with the CCST (P < 0.02). Steers fed BMRT increased feed margin (P = 0.05) and net return (P = 0.02) compared to those fed CCST throughout the trial. Overall data in this study indicate that feeding the BMRT to growing beef steers enhanced ruminal fermentation and beneficially shifted VFA profiles, which contributed to improved growth performance and economic performance of steers fed the BMRT.

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