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United States Department of Agriculture

Agricultural Research Service

Title: Effects of Dietary Crude Protein on Serum and Urine Urea Nitrogen in Feedlot Steers

Authors
item Gueye, A - TEXAS TECH
item Richardson, C. - TEXAS TECH
item Mikus, J. - TEXAS TECH
item Nunnery, G. - TEXAS TECH
item Cole, Noel
item Greene, L. - TAES

Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: April 22, 2003
Publication Date: June 22, 2003
Citation: Gueye, A., Richardson, C. R., Mikus, J. H., Nunnery, G. A., Cole, N. A., Greene, L. W. Effects of Dietary Crude Protein on Serum and Urine Urea Nitrogen in Feedlot Steers. 2003. Journal of Animal Science. 2003. v. 81(Suppl.1). p. 210. Abstract No. M130.

Technical Abstract: We evaluated the effects of dietary CP concentration and source on serum urea N (SUN) and urine urea N (UUN). A metabolism trial with three collection periods (approximately d 35, 95, and 155 on feed) was conducted using twenty seven crossbred steers (average BW = 353.2 ± 8.4 kg). Treatments were arranged in a factorial design and consisted of three dietary CP concentrations (11.5, 13.0, and 14.5%) and three supplemental urea:cottonseed meal (CSM) ratios (100:0, 50:50, and 0:100 of supplemental nitrogen). During each collection period, steers were housed in individual metabolism stalls; urine collected and frozen; and blood samples obtained via jugular venipuncture. Collection periods consisted of a 2- to 5-d adjustment period followed by a 5-d collection period. On d 35 on feed, SUN as steers entered the stalls (SUN-in) increased linearly (P = 0.001) with increasing CP concentration. Urine urea nitrogen (mg/dL) responded linearly (P < 0.05) to increasing CP concentration, and steers in the 50:50 treatment tended (P = 0.10) to have higher UUN than steers in the 0:100 treatment. On d 95 on feed, SUN-in and SUN as steers exited the stalls (SUN-out) increased linearly (P = 0.03 and P = 0.009, respectively) when dietary CP increased from 11.5 to 14.5%. Urine urea N linearly (P < 0.0001) increased with increasing CP. On d 155 on feed, SUN-in and SUN-out linearly increased (P = 0.005 and P = 0.003, respectively) with increasing CP concentration. Urine output increased linearly (P = 0.009) when CP level increased from 11.5 to 14.5%. Increasing CP concentration produced a linear increase (P = 0.04) in UUN (mg/dL). Urine urea N (% of UN) decreased linearly (P = 0.007) with increasing CP. Results suggest that the amount and degradability of dietary protein affect urea metabolism by feedlot steers, as evidenced by changes in serum and urinary urea nitrogen.

Last Modified: 4/21/2014
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