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United States Department of Agriculture

Agricultural Research Service

Title: THE EFFECTS OF DIETARY CRUDE PROTEIN CONCENTRATION ON NITROGEN ABSORPTION AND RETENTION BY FEEDLOT STEERS)

Author
item Gueye, A.
item Richardson, C.
item Mikus, J.
item Nunnery, G.
item Cole, Noel - Andy
item Greene, L.

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. The Effects of Dietary Crude Protein Concentration on Nitrogen Absorption and Retention by Feedlot Steers. Journal of Animal Science. 2003. v. 81(Suppl.1). p. 110. Abstract No. M129.

Interpretive Summary:

Technical Abstract: Twenty seven crossbred steers (average BW = 353.2 ± 8.4 kg) were used in a metabolism trial with three collection periods (approximately 35, 95, and 155 d on feed) to evaluate the effects of dietary CP source and concentration on nitrogen balance by steers. 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 N). During each nutrient collection period steers were housed in individual metabolism stalls and urine and feces excreted were collected and frozen. Collection periods consisted of a 2- to 5-d adaptation period followed by a 5-d collection period. On d 35 on feed, total N excretion increased linearly (P = 0.002) with increasing CP concentration. Nitrogen absorbed (g/d) and N retained (g/d)linearly increased (P < 0.0001 and P = 0.01, respectively) with increasing CP concentration. On d 95 on feed, total N excretion linearly increased (P < 0.0001) with increasing CP concentration. Nitrogen absorbed (g/d) and N retained linearly increased (P < 0.0001 and P = 0.001, respectively) when CP increased from 11.5 to 14.5%. On d 155 on feed, DM digestibility decreased linearly (P < 0.05) with increasing dietary CP. Fecal N excretion increased linearly (P < 0.0001) with increasing CP. Nitrogen absorbed (g/d) decreased linearly (P = 0.03) with decreasing urea:CSM ratio. Nitrogen absorbed (% of intake) increased quadratically (P = 0.05) with decreasing urea:CSM ratio. As days on feed increased, total N excretion also increased (P < 0.02). Based on our observations, feeding growing steers diets containing 11.5 to 13.0% CP and supplemented with higher proportions of degradable protein may potentially optimize N utilization and potentially reduces N losses to the environment.

Last Modified: 8/24/2016
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