A comparison of nitrogen utilization and urea metabolism between Tibetan and fine-wool sheep

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dc.contributor.author Zhou, J. W.
dc.contributor.author Mi, J. D.
dc.contributor.author Titgemeyer, Evan C.
dc.contributor.author Guo, X. S.
dc.contributor.author Ding, L. M.
dc.contributor.author Wang, H. C.
dc.contributor.author Qiu, Q.
dc.contributor.author Li, Z. P.
dc.contributor.author Long, R. J.
dc.date.accessioned 2016-03-28T19:16:06Z
dc.date.available 2016-03-28T19:16:06Z
dc.identifier.uri http://hdl.handle.net/2097/32186
dc.description Citation: Zhou, J. W., Mi, J. D., Titgemeyer, E. C., Guo, X. S., Ding, L. M., Wang, H. C., . . . Long, R. J. (2015). A comparison of nitrogen utilization and urea metabolism between Tibetan and fine-wool sheep. Journal of Animal Science, 93(6), 3006-3017. doi:10.2527/jas2014-8865
dc.description To study metabolic adaptation to harsh foraging conditions, an experiment was conducted to characterize and quantify N utilization efficiency and urea metabolism in Tibetan and fine-wool sheep fed 4 levels of dietary N (11.0, 16.7, 23.1, and 29.2 g N/kg DM) in 2 concurrent 4 x 4 Latin square designs. Urea kinetics were determined using continuous intrajugular infusions of (NN)-N-15-N-15-urea. Urinary excretions of total N and urea N increased linearly (P < 0.001) with dietary N and were not different between breeds (P >= 0.37). Fecal N excretion increased with dietary N for Tibetan sheep but not for fine-wool sheep (linear dietary N x breed; P < 0.05). Nitrogen retention (both amount per day and percentage of N intake) increased with increasing dietary N concentration (P < 0.001), and the rates of increase were greater in fine-wool than in Tibetan sheep (linear dietary N x breed and cubic dietary N x breed; P < 0.05). In Tibetan sheep, N retention as a percentage of intake was greatest for diets containing 16.7 g N/kg DM, whereas it was maximal for fine-wool sheep when the diet contained 23.1 g N/kg DM. Urea N entry rate, urea N recycled to the gastrointestinal tract (GIT), and urea N returned to the ornithine cycle all increased with dietary N (P < 0.05), and all were greater in Tibetan than fine-wool sheep for the 11.0 g N/kg DM diet but were greater in fine-wool than Tibetan sheep for the diet with 29.2 g N/kg DM (linear dietary N x breed; P < 0.05). Urea N excreted in feces, both amount and fraction of GIT entry rate, was less in Tibetan than finewool sheep for the 11.0 and 16.7 g N/kg DM diets but similar for diets with 23.1 or 29.2 g N/kg DM (linear dietary N x breed; P < 0.01). For the lowest-protein diet, the fraction of urea N production recycled to the GIT was greater in the Tibetan than fine-wool sheep (88% vs. 82%), but for the diet with 29.2 g N/kg DM it was greater for fine-wool than Tibetan sheep (46% vs. 39%; linear dietary N x breed; P < 0.05). Plasma urea N increased more rapidly in response to increasing dietary N concentration for fine-wool sheep than for Tibetan sheep (linear dietary N x breed; P < 0.05). Urea tubular load and the amount and percentage of urea reabsorbed by the kidney were greater in Tibetan than fine-wool sheep (P < 0.05). These results suggest that Tibetan sheep have mechanisms that allow them to utilize N more efficiently than the fine-wool sheep when dietary N is inadequate.
dc.relation.uri https://doi.org/10.2527/jas.2014-8865
dc.rights Copyright © 2015. American Society of Animal Science. 
dc.rights.uri http://www.sherpa.ac.uk/romeo/issn/0021-8812/
dc.subject Adaptation
dc.subject Dietary Nitrogen Utilization
dc.subject Qinghai-Tibetan Plateau
dc.subject Tibetan Sheep
dc.subject Urea Recycling
dc.subject Low-Quality Forage
dc.title A comparison of nitrogen utilization and urea metabolism between Tibetan and fine-wool sheep
dc.type Article
dc.date.published 2015
dc.citation.doi 10.2527/jas2014-8865
dc.citation.epage 3017
dc.citation.issn 0021-8812
dc.citation.issue 6
dc.citation.jtitle Journal of Animal Science
dc.citation.spage 3006
dc.citation.volume 93
dc.contributor.authoreid etitgeme


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