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Ruminant Nutrition and Forage Utilization
Asian-Australasian Journal of Animal Sciences 2005;18(6): 795-801.
DOI: https://doi.org/10.5713/ajas.2005.795    Published online November 26, 2005.
Urea Kinetics in Wethers Exposed to Different Ambient Temperatures at Three Dietary Levels of Crude Protein
Sangsoo Sun, Robert J. Christopherson
Eighteen Suffolk wether lambs (BW = 24 kg) were chronically exposed to temperatures of cold (2째C) or warm (22째C). The experimental design consisted of a 2횞3 factorial with a single crossover of environment treatment. The sheep were closely shorn and were housed in individual metabolic crates in controlled environment rooms. Sheep consumed pelleted diets ad libitum, which consisted of mainly barley grain and brome grass, and diets contained 7, 11 or 14% crude protein (CP). Animals were catheterized via one jugular vein with a PVC catheter and received a single injection of 60-65 Ci of [14C]urea. Plasma urea-N (PUN), urinary urea (UU), and carbon specific radioactivity were measured. Urea metabolism was not affected by environment. Percent urea recycling and urea space clearance were highest (p<0.05) on the low nitrogen diet. Urea pool was increased (p<0.10) for the 14% CP diet. Both UU and PUN concentration were positively related (p<0.01) with diet CP content. Therefore, dietary CP content significantly influenced urea metabolism, however, cold exposure did not alter those parameters.
Keywords: Urea Recycling; Urea Flux; Crude Protein; Cold; Sheep
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