Journal of Animal Science, Vol 80, Issue 5 1344-1351, Copyright © 2002 by American Society of Animal Science

JOURNAL ARTICLE

Nitrogen metabolism of beef steers fed endophyte-free tall fescue hay: effects of ruminally protected methionine supplementation

S. L. Archibeque, J. C. Burns and G. B. Huntington
Animal Science Department, North Carolina State University, Raleigh 27695, USA.

Level of nitrogen (N) intake and ruminally protected methionine supplementation were evaluated in eight Angus growing steers (initial BW 253+/-21 kg, final BW 296+/-21 kg) in a replicated 4+/-4 Latin square design. The steers were fed two endophyte-free tall fescue (Festuca arundinacea) hays that contained 2.2 (LO) or 2.8% (HI) of DM as N and were either supplemented or not with ruminally protected methionine (10 g metabolizable methionine/d). Diets were fed to provide adequate energy for 0.5 kg ADG and sufficient protein for maintenance (LO), or protein to support 0.5 kg ADG (HI). Following at least 14 d of adjustment, N balance was measured for 6 d. Isotopic urea was infused (15N15N-urea, 0.164 mmol urea N/h) via a jugular catheter for 56 h and urine was collected from 48 to 56 h to measure urea kinetics. Jugular blood was collected during the balance trial, and serum was analyzed for serum urea N (SUN). By design, daily N intake was greater (P < 0.05) for HI (112 g) than for LO (89 g). Compared with LO, steers when fed HI had greater (P < 0.05) daily DMI (4,217 vs 4,151 g), fecal N (34.4 vs 31.2 g), N digested (77.1 vs 57.7 g), urine N (48.3 vs 37.5 g), urine urea N excretion (34.6 vs 24.8 g), and N retained (29.8 vs 21.1 g). When fed HI steers also had higher (P < 0.05) urine urea N concentration (276 vs 219 mM), SUN (8.7 vs 6.7 mM), N digestibility (69.1 vs 64.9%), percentage of urinary N present as urea (71.5 vs 66.7%, P < 0.053), and rate of urea N production (59.6 vs 49.2 g/d) but lower (P < 0.05) percentage of urea N produced that was returned to the ornithine cycle (15.03 vs 19.2 1%) than when fed LO. Methionine supplementation decreased daily urine N (41.2 vs 44.6 g, P = 0.10) and increased both the amount of N retained daily (27.9 vs 23.7 g, P < 0.089) and the percentage of N digested that was retained (40.4 vs 34.6%, P < 0.094). In summary, supplemental methionine met a specific dietary limitation by increasing the amount of digested N that was retained by the steers.

This article has been cited by other articles:

				C. K. Reynolds and N. B. Kristensen Nitrogen recycling through the gut and the nitrogen economy of ruminants: An asynchronous symbiosis J Anim Sci, April 1, 2008; 86(14_suppl): E293 - E305. [Abstract] [Full Text] [PDF]

				Z. H. Sun, Z. L. Tan, S. M. Liu, G. O. Tayo, B. Lin, B. Teng, S. X. Tang, W. J. Wang, Y. P. Liao, Y. F. Pan, et al. Effects of dietary methionine and lysine sources on nutrient digestion, nitrogen utilization, and duodenal amino acid flow in growing goats J Anim Sci, December 1, 2007; 85(12): 3340 - 3347. [Abstract] [Full Text] [PDF]

				G. B. Huntington, J. C. Burns, and S. L. Archibeque Urea metabolism in beef steers grazing Bermudagrass, Caucasian bluestem, or gamagrass pastures varying in plant morphology, protein content, and protein composition J Anim Sci, August 1, 2007; 85(8): 1997 - 2004. [Abstract] [Full Text] [PDF]

				N. E. Sunny, S. L. Owens, R. L. Baldwin VI, S. W. El-Kadi, R. A. Kohn, and B. J. Bequette Salvage of blood urea nitrogen in sheep is highly dependent on plasma urea concentration and the efficiency of capture within the digestive tract J Anim Sci, April 1, 2007; 85(4): 1006 - 1013. [Abstract] [Full Text] [PDF]

				X. Hao, P. S. Mir, M. A. Shah, and G. R. Travis Influence of Canola and Sunflower Diet Amendments on Cattle Feedlot Manure J. Environ. Qual., July 5, 2005; 34(4): 1439 - 1445. [Abstract] [Full Text] [PDF]

				R. A. Kohn, M. M. Dinneen, and E. Russek-Cohen Using blood urea nitrogen to predict nitrogen excretion and efficiency of nitrogen utilization in cattle, sheep, goats, horses, pigs, and rats J Anim Sci, April 1, 2005; 83(4): 879 - 889. [Abstract] [Full Text] [PDF]