Document Type

Thesis - Open Access

Award Date

2022

Degree Name

Master of Science (MS)

Department / School

Animal Science

First Advisor

Zachary Smith

Keywords

Backgrounding, Corn Silage, Feedlot, Finishing, Forage, Roughage

Abstract

The two studies in this thesis were conducted to: 1) investigate the impact of corn silage moisture content and kernel processing at harvest on growth performance, efficiency of dietary net energy utilization, and carcass traits in finishing steers when fed at 20% DM inclusion in diets containing modified distillers grains plus solubles; and 2) determine the influence of equal cumulative roughage inclusion in a single diet or twodiet system during a 210-d backgrounding-finishing period in pre-conditioned beef steers on growth performance responses, efficiency of dietary net energy (NE) utilization, and carcass traits. Experiment 1 was a 112-d finishing experiment conducted at the Southeast Research Farm (SERF) near Beresford, SD using 192 single source, Red Angus influenced steers (initial BW = 446 ± 28.3 kg). This study used 6 replicate pens (24 total pens) of 8 steers assigned to one of 4 dietary treatments (2 x 2 factorial arrangement). Factors included silage maturity at harvest time (HT) and kernel processing (KP). Treatments were arranged as a 2 x 2 factorial with the factors of HT (1/2 to 2/3 Milkline [(ML)]) or (black layer [BL]) with (KP+) or without (KP-) kernel processing. Steers were blocked by batch fraction (n = 6) and pen served as the experimental unit. The model included the effects of harvest time, processing, and their interaction. Block was included as a random factor. No harvest time × KP interaction was detected (P ≥ 0.26) for any parameters related to the efficiency of dietary NE utilization. Comparative by harvest time indicates that delayed harvest enhanced corn silage NEm by 6% and KP decreased apparent NEm value of corn silage by 9% compared to current feeding standards. No HT × KP interaction (P ≥ 0.08) was detected for any carcass traits except the distribution of USDA Prime carcasses (P = 0.04). Steers from ML/KP- had fewer (P = 0.05) USDA Prime carcasses compared to ML/KP+, BL/KP-, and BL/KP+. Harvest time (P ≥ 0.07) and KP (P ≥ 0.07) had no appreciable influence on any carcass trait parameters. These data indicate that corn silage harvest can be delayed without detriment to growth performance and kernel processing does not enhance the apparent feeding value of corn silage when corn silage is fed as the sole roughage component of a feedlot finishing diet (i.e. 20% inclusion DM basis). Experiment 2 used 46 single source, crossbred beef steers (initial BW = 281 ± 40.4 kg) in a 210-d background-finish experiment at the Ruminant Nutrition Center (RNC) in Brookings, SD. This study used five replicate 7.6 x 7.6-meter concrete pens (10 total pens) with 4 or 5 steers assigned to one of two dietary treatments. The target cumulative roughage for both treatments was 16% over the 210-d backgroundfinish period. Treatments included: 1) Single Diet (1D), one diet throughout the feeding period, (16% Roughage) 1.34 Mcal/kg NEg 210-d, 2) Two Diet (2D), initial growing diet, (25% Roughage) 1.25 Mcal/kg NEg for 98-d, transition diet, (16% Roughage) 1.34 Mcal/kg NEg for 14-d, finishing diet, (7% Roughage) 1.43 Mcal/kg NEg for 98-d. All steers were implanted initially (d 1) with a 100 mg trenbolone acetate (TBA) and 14 mg estradiol benzoate (EB) implant (Synovex Choice, Zoetis) and re-implanted with a 200 mg TBA and 28 mg EB implant (Synovex-Plus, Zoetis) on d 112. Fresh feed was manufactured once daily for each treatment in a single batch using a stationary mixer and bunks were managed using a slick bunk management approach. Data were analyzed as a randomized complete block design with pen as the experimental unit. Average daily gain (ADG) tended (P = 0.06) to be 9.5% greater for 1D compared to 2D during the backgrounding portion and ADG was increased 11.3% (P = 0.01) for 2D compared to 1D during the finishing phase of the experiment. Cumulative ADG did not differ between treatments (1.61 vs. 1.62 ± 0.046 kg/d) for 1D and 2D, respectively. Cumulative observed dietary NEm and NEg did not differ (P ≥ 0.96) between treatments. There were no differences (P ≥ 0.18) detected between treatments for HCW, DP, REA, RF, USDA marbling score, KPH, yield grade, retail yield, EBF, or body weight at 28% estimated EBF. It is concluded that Northern Plains feedlot producers can feed a single growingfinishing diet to preconditioned beef steers with minimal effects on overall growth performance or carcass traits.

Publisher

South Dakota State University

Included in

Beef Science Commons

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Rights Statement

In Copyright