Le recyclage de l'azote dans le tractus gastro-intestinal Orskov E.R., Whitelaw F.G. in Tisserand J.-L. (ed.). Séminaire sur la digestion, la nutrition et l'alimentation du dromadaire Zaragoza : CIHEAM Options Méditerranéennes : Série A. Séminaires Méditerranéens; n. 2 1989 pages 99 Article available on lin e / Article dispon ible en lign e à l’adresse : -------------------------------------------------------------------------------------------------------------------------------------------------------------------------http://om.ciheam.org/article.php?IDPDF=CI000433 -------------------------------------------------------------------------------------------------------------------------------------------------------------------------To cite th is article / Pou r citer cet article -------------------------------------------------------------------------------------------------------------------------------------------------------------------------Orskov E.R., Whitelaw F.G. Le recyclage de l' azote dan s le tractu s gastro-in testin al. In : Tisserand J.-L. (ed.). Séminaire sur la digestion, la nutrition et l'alimentation du dromadaire. Zaragoza : CIHEAM, 1989. p. 99 (Options Méditerranéennes : Série A. Séminaires Méditerranéens; n. 2) -------------------------------------------------------------------------------------------------------------------------------------------------------------------------- http://www.ciheam.org/ http://om.ciheam.org/ CIHEAM - Options Mediterraneennes de l'azote E. R. ORSKOV F. WHITELAW ROWET RESEARCH INSTITUTE ABERDEEN (ENGLAND) - cditrogen re-cycling to the gastro-intestinal tractb. The ability from the blood to the gastrointestinal tract can be major nutritional significance under arid and semi-arid conditions wherethe available food supply frequently consist ofpoor-qualityforages, low in availableh? Under these conditions the transfer urea to therumen allows normal microbial activity in feed intake which would and rumenfunction to be maintained andso delays for a time the depression in organic matter digestibility and otherwise ensue.Although urea recycling can account for over 90% urea synthesis rate when dietary protein supply is deficient, it is important to recognize that loss from the body still occurs and the process will eventually wind-dowm if undernutrition is prolonged, At the other extreme urea recyclingas high as 50% it is not known whether this confers any nutritional advantage tothe host. Although many theories have been advanced over thepast thirv years, the spec@ mechanisms involved in the control urea transfer to thegut have notyet been completely resolved, One obvious route urea recycling via saliva and urea Concentrations in saliva are known to be highly correlated with concentrations in plasma This situation however, suggests that the quantities transferredmay well be minimal when the microbial needs for N are greatest. is regulated The alternative route bypassage across therumen wall andhere opinionsdiffer to whether it a purely passive process or by factors such as ammonia concentration gradient,effects of ammonia on bacterial urease activities or changes in the permeability the rumen epithelium, mediated by local concentrations fermentation end is accumulating also that considerable movement urea cai occur across thepost-rumen digestive tract and that the control urea transfer at these sites probably differentfrom that in the rumen. an attempt to resolve some these problems, comparisons have been made between ruminants nourished by normalfeeds and those sustained wholly by intragastric infusions all nutrients. These experiments have shown that fermentation in the rumen not a prerequisite for normal urea recycling since the quuwtities trmferred to the gastro-intestinal tract were similar in the two situations. subsequent trials, the establishement microbial fermentations in either thefore-stomach or the hind-gut animals otherwise nourished solely byinjiuion had no effect on the total quantity urea recycled to the gut. The possible contribution recycled urea to.the nitrogen economy the ruminant in adverse dietary situations will be discussed words: Dromedary, - à de à d'une à la quantité à une activité où la de un continue à ne peut que 50%de celui de de 90% en cas des que beaucoup de synthèse, il A d'azote, mais on ne sait pas si un ces 30 le mécanisme spécifique n'a jamais été complètementélucidé. La salive constitue une voie évidentede de les la à celles du élevés. passage à mais ici les quant à s'ils'agit d'un simple phénomène passif ou on de effects l'activité des ou des l'épithélium de des l'existence d'un à le digestif de celui Afin de voie de tous les éléments n'est de l'intestin d'un On discute ausside la Options n'a pas l'intestin. de - des - n.O 2 - 1989: 99 Serie A: Seminaires mediterraneens