Document Type

Thesis - Open Access

Award Date

2024

Degree Name

Master of Science (MS)

Department / School

Animal Science

First Advisor

Warren C Rusche

Abstract

Two randomized complete block design experiments were conducted to: 1) examine the effects of soybean meal with or without additional soybean hulls in replacement of modified corn distillers grains plus (MDGS) solubles on growth performance efficiency of dietary net energy utilization and carcass traits responses in finishing beef steers, 2) determine if partial or complete replacement of dried distillers grains plus solubles (DDGS) with solvent-extracted soybean meal (SBM) in diets based upon high-moisture ensiled corn influences growth performance, efficiency of dietary net energy utilization, sera urea-N (SUN) concentrations, or carcass traits in finishing beef steers. Experiment 1 was a 118-d finishing experiment conducted at the Southeast Research Farm (SERF) near Beresford, SD using single source, Black Angus influence steers (initial shrunk BW = 435 ± 23.2 kg). This study used 6 replicate pens (24 total pens) of 8 steers assigned to one of three dietary treatments. Dietary treatments included: 1) MDGS fed at 15% diet DM (MDGS), 2) MDGS replaced by soybean meal and corn (9 and 6% of DM, respectively; SBM), 3) MDGS replaced by soybean meal and soyhull pellets (9 and 6% of DM, respectively; SBM-SBH). Steers were blocked by batch fraction and pen served as the experimental unit. The model included the fixed effects of treatment and block. No differences amongst treatments (P ≥ 0.11) were observed for carcass-adjusted final BW, dry matter intake (DMI), average daily gain (ADG), or feed efficiency. Dietary treatment had no effect (P ≥ 0.11) on hot carcass weight (HCW), dressing percentage, ribeye area, rib fat, marbling score, USDA Yield Grade, percent empty body fat (EBF), or final body weight adjusted to 28% empty body fat (EBF). Distribution of USDA Quality or Yield grades were unaffected by treatment (P ≥ 0.39). Dietary treatment did not affect liver abscess incidence and severity (P = 0.11). Net energy values calculated from animal performance agreed closely with tabular estimates with observed to expected ratios for net energy equalling one. In this experiment, feeding supplemental protein sources with enhanced diet conditioning attributes and greater concentrations of ruminally undegradable protein provided no advantage to cattle performance. Experiment 2 was a 139-d finishing experiment conducted at the Ruminant Nutrition Center (RNC) in Brookings, SD using Continental × British crossbred steers (initial shrunk BW = 381 ± 37.1 kg). This study used 6 replicate pens (24 total pens) of 7 or 8 steers assigned to one of three dietary treatments. Dietary treatments included: 1) DDGS fed at 20% DM (15.4% CP, 8% RDP, and 1.90% NPN; DDGS), 2) SBM replacing 50% of DDGS (16.4% CP, 9% RDP, and 0.96% NPN; SBM50), 3) SBM replacing 100% of DDGS (17.4% CP, 10% RDP, and 0.05% NPN; SBM100). The model included treatment and block (initial BW) as fixed effects; pen was the experimental unit. Treatment effects were evaluated for linear and quadratic components by the method of orthogonal polynomials. Whole blood was collected and harvested as sera on d 77, 105, and 139 to determine circulating concentrations of sera urea-N. On a live basis, feeding SBM linearly increased final BW ( P = 0.03) but did not affect DMI (P ≥ 0.33). Dietary treatment tended to affect ADG (Quadratic; P = 0.09) and G:F (quadratic; P = 0.06) with the greatest positive effects in SBM50 fed cattle. Carcass adjusted final BW was calculated by dividing hot carcass weight (HCW) by a common dressing percentage of 0.625 (cFBW). No differences were noted for carcass adjusted final BW, average daily gain (ADG), dry matter intake (DMI), or feed efficiency (P ≥ 0.18). Dietary treatment tended to affect G:F (quadratic; P = 0.10) and SBM increased the apparent efficiency of energy capture (Linear; P = 0.01). The total and partial substitution NEg values were 17.0 and 27.5% greater than DDGS respectively. Dietary treatment had no effect (P ≥ 0.22) on HCW, rib fat, or marbling score. Complete replacement of DDGS with SBM linearly increased rib eye area (REA) by 1% (P = 0.02), but linearly decreased dressing percentage (DP; P = 0.03). Distribution of USDA quality or yield grades were unaffected by treatment (P ≥ 0.36). Feeding SBM as a replacement of DDGS altered the distribution of liver scores. Steers from SBM100 had fewer livers classified as normal and a greater proportion of livers classified as severely (A+ or Greater) abscessed (P = 0.05). No treatment × day interaction was observed for sera urea-N (P = 0.20). However, day (P < 0.01) and treatment (P < 0.01) effects were observed. Throughout the duration of the trial the SBM100 treatment maintained greatest sera urea-N concentrations, the SBM50 treatment being intermediate, and the DDGS treatment had least concentrations of sera urea-N (P < 0.01). Further, sera urea-N concentrations increased overtime from d 77 to d 139 (P < 0.01). In this experiment, replacement of DDGS with SBM increased REA and tended to decrease DP and had a quadratic tendency to improve feed conversion with no other observed effects on carcass adjusted growth performance or carcass traits.

Publisher

South Dakota State University

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Beef Science Commons

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Rights Statement

In Copyright