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Thesis - University Access Only
Master of Science (MS)
beef cattle, blood ammonia, in situ, non-protein nitrogen
The objectives of this experiment were to compare N fluxes of Optigen, a slowrelease NPN source, with urea; whether pelleting affects Optigen N release; and N source effects on ruminal fiber digestibility. Dietary crude protein treatments were soybean meal (SBM), ruminally dosed Optigen (OD), Optigen incorporated into a concentrate pellet (OP), or ruminally dosed urea (UD). Diets were 50% forage (oat hay; 5.5% CP, 66% NDF) and 50% pelleted concentrate feed. Dietary CP was higher for OD and UD diets than for SBM and OP (12.6 v 11.2%; P < 0.01). Diets were fed to ruminally fistulated steers (BW 387 ± 28.9 kg) in a 4x4 Latin square designed experiment. Concentreate was fed and pulse doses of NPN occurred at 0800. Chronic sampling of rumen fluid and blood was done to follow postprandial changes in urea and ammonia concentrations. Mean rumen ammonia-N (RAN) concentrations differed among diets (4.9a, 8.9a, 6.6a, and 24.8b mg/dl, respectively; P < 0.01). A diet by time interaction occurred because of 60 min post feeding RAN concentrations of 8.7a, 31.2a, 22.1a, and 127.0b mg/dl, respectively (P < 0.01). Differences in plasma urea-N (PUN) mean concentrations (9.8a, 9.6a, 9.6a, and 12.3b mg/dl, respectively) included effects of time and diet by time interactions (P ≤ 0.01). At 60 min after dosing, PAN concentrations were highest for UD (P < 0.05). Mean plasma ammonia-N (PAN) concentrations differed among diets (0.6a, 0.6a, 0.7b, and 0.9c mg/dl, respectively; P ≤ 0.05). At 4 h after dosing, the UD diet caused lower (P ≤ 0.01) VFA concentration than other diets. At 1 and 4 h after dosing, UD diet caused higher ruminal pH than all other diets (P ≤ 0.01). Optigen had a slower rate of N release than urea, and was not adversely affected by pelleting. Because of a 16 h lag time after dosing, diet caused minimal differences in fermentation.
Library of Congress Subject Headings
beef cattle -- Feeding and feeds
Urea as feed
Nitrogen in animal nutrition
Fiber in animal nutrition
Includes bibliographical references (pages 29-35)
Number of Pages
South Dakota State University
In Copyright - Educational Use Permitted
Cox, Carrie LaVonne, "The Effects of Slow-release Urea on Nitrogen Metabolism and Fiber Digestion in Steers Fed High-forage Diets" (2012). Theses and Dissertations. 1340.