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Effects of Urea Supplementation in Finishing Diets Containing 25% Modified Distillers Grains on Growth and Carcass Characteristics in Yearling Steers, and in Situ Protein Degradation of Commonly Used Feedstuffs in High Concentrate Rations
Thesis - University Access Only
Master of Science (MS)
DIP, Urea, distillers grains, beef cattle
Two experiments were conducted to determine: 1) the effects of urea supplementation in finishing rations containing elevated levels of DG; and 2) to determine rumen degradability of protein in various concentrates commonly used in beef finishing diets. The first experiment was designed to evaluate the effects of urea supplementation in DRC/HMC based diets containing 25% MDGS. Finishing diets containing elevated levels of distillers grains may contain excessive concentrations of CP, yet still be deficient in degradable intake protein (DIP). To address this situation, finishing diets containing 25% modified distillers grains (MDGS), 40% dry rolled corn, 20% high moisture corn, 12% corn silage, and 3% dry supplement (DM basis) were supplemented with 0 (CON), 0.36 (Low-U), or 0.72% (High-U) urea. Diets contained 13.3 and 6.6, 14.2 and 7.6, and 15.2 and 8.5% CP and DIP for CON, Low-U, and High- U, respectively. Two hundred fifty-one, predominately Angus yearling steers were blocked by source and randomly allotted to 24 pens. Steers in block 1 (n = 71; BW = 388 ± 41 kg) were housed in nine partially roofed concrete-surfaced pens. Block 2 cattle (n = 180; BW = 375 ± 24 kg) were housed in fifteen soil-surfaced dry lot pens. Cattle were fed for 98 and 144 days for blocks 1 and 2, respectively, before harvest at a commercial abattoir. Preplanned contrasts evaluated CON v supplemental urea, and Low-U v High- U, respectively. Calculated DIP requirements for microbial needs were 68 g/d deficient for CON, but in excess 33.7 and 132.6 g/d for Low-U and High-U (P < 0.001). Body weights, ADG, and G:F were not different between treatments (P ≥ 0.08). Marbling score was increased (P = 0.04) in CON (524) steers compared to Low-U (495) and High- U (491). This resulted in 60.0% of carcasses in upper 2/3 Choice and Prime grades for CON compared to 40.6% for Low-U and 46.5% for High-U (P = 0.05). No other carcass trait differences were observed (P ≥ 0.28). Results suggest that urea supplementation to finishing diets containing 25% MDGS does not include feedlot performance, but can decrease quality grade yearling steers. The second experiment was designed to quantify rumen degradability of protein in feedstuffs commonly used in high concentrate diets. Research suggests that greater concentrations of DIP in finishing diet may be present than what published values predict. To address this hypothesis an in situ trial was conducted to determine DIP content of various feedstuffs commonly used in feedlot diets in steers fed high concentrate diets. Three canulated yearling steers were used to determine in situ degradability of protein in dry-rolled corn (DRC), high-moisture corn (HMC), steamflaked corn (SFC), soybean mean, corn distillers grains (dry, modified, and wet; DDGS, MDGS, and WDGS), and mixed sorghum/corn distillers grains (dry and wet; SCDGS and WSCDGS). Steers were adapted to a high concentrate diet consisting of dry-rolled corn (71% of DM), DDGS (15% of DM), chopped alfalfa hay (10% of DM) and a liquid supplement (4% of DM). Steers were fed to reach peak intake prior to the start of the trial. Results show a significant increase in DIP content in all feedstuffs compared to published values. HMC had the greatest degradability (89.7% DIP, SD = .04) compared to other feedstuffs. Dry sorghum/corn distillers grains was lowest (51.5% DIP, SD= 4.66). Dry-rolled corn was similar to soybean meal (77.9 and 72.6% DIP respectively) but greater than DDGS, MDGS, WDGS, and WSCDGS (66.5, 70.2, 70.4 and 72.1% DIP respectively). Results suggest slower rate of passage in cattle fed finishing diets allows for greater microbial degradation of protein, yielding an increased DIP concentration in the diet than predicted using published values.
Library of Congress Subject Headings
Beef cattle -- Feeding and feeds
Urea as feed
Beef cattle -- Growth
Beef cattle -- Carcasses
Includes bibliographical references
Number of Pages
South Dakota State University
In Copyright - Non-Commercial Use Permitted
Garbel, Levi, "Effects of Urea Supplementation in Finishing Diets Containing 25% Modified Distillers Grains on Growth and Carcass Characteristics in Yearling Steers, and in Situ Protein Degradation of Commonly Used Feedstuffs in High Concentrate Rations" (2014). Electronic Theses and Dissertations. 1545.