QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Biddle, G. N. Articles by Trout, J. R. Search for Related Content PubMed PubMed Citation Articles by Biddle, G. N. Articles by Trout, J. R.

Labile Nitrogen Reserves and Plasma Nitrogen Fractions in Growing Cattle^1,2,

Rutgers University, New Brunswick, New Jersey 08903

The existence and magnitude of labile nitrogen (N) reserves were studied in growing cattle using a dietary N depletion-repletion technique. Blood parameters and urinary N excretion patterns were monitored. Blood hematocrit (Ht) did not respond to reduced ingested N until after week 3 of depletion at which time it began to fall. About 3 weeks of repletion regime was required before Ht values increased again. Plasma protein and albumin decreased from 6.05 and 2.70 g during standardization to 5.44 and 2.44 g/100 ml after 5 weeks of depletion and did not approach predepletion levels until week 6 of repletion. Plasma urea N decreased from 16 mg in standardization to 0.8 mg/100 ml in depletion and required 3 weeks of repletion treatment to attain a peak of 18 mg/100 ml. Labile N reserves were determined by integrating the areas from total urinary N excretion curves obtained during depletion and repletion periods. On a live body weight basis labile N represented 5.6% of total body N. When computed on an empty body weight basis (does not include weight of gastrointestinal tract), labile N totalled 6.0%. The magnitude of labile N stores as a percentage of total body N was 44% greater in steers with a mean body weight of 280 kg compared with animals weighing 144 kg.

KEY WORDS: • nitrogen • depletion-repletion • labile nitrogen reserves • plasma nitrogen/protein • ruminants

¹ Paper of the Journal Series. New Jersey Agricultural Experiment Station. Rutgers University, New Brunswick, N.J. 08903.

² Preliminary report of these results was presented at the Annual Meeting of the American Society of Animal Science, Blacksburg, Va. 1972. J. Anim Sci. 35, 259. (Abstr.)

³ Present address: Southeast Utilization Research Center, National Marine Fisheries Service, Regents Drive. University of Maryland Campus, College Park, Md. 20740.

⁴ Graduate Program in Nutrition, Cook College.

⁵ Statistician, Cook College.

Manuscript received 19 May 1975.

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]

				N. A. Cole and R. W. Todd Opportunities to enhance performance and efficiency through nutrient synchrony in concentrate-fed ruminants J Anim Sci, April 1, 2008; 86(14_suppl): E318 - E333. [Abstract] [Full Text] [PDF]