Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 4/22/2003
Publication Date: 6/22/2003
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. Interpretive Summary:
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.