title: Effect of level and origin of rumen degradable nitrogen on rumen microbial growth and nitrogen utilisation efficiency of animals fed maize silage at maintenance.
abstract: Isoenergetic maize silage diets, fed at maintenance to 24 suckling cows (Exp. 1) and to 3 (Exp. 2) or 4 (Exp. 3) rumen fistulated sheep, were compared with a urea and controlled release NPN diet (Exps. 1 and 2) and with a protein-N supplemented diet (Exp. 3). Supplementation increased blood urea concentrations (44.7 +/- 22.3 vs. 97.6 +/- 23.7 mg urea-N x L(-1)) (Exp. 1) and renal urea excretion (2.5 +/- 1.1 vs. 7.6 +/- 1.8 g urea-N x d(-1)) (Exps. 2 and 3), whereas blood allantoin concentrations (286.7 +/- 77.0 micromol x L(-1)) (Exp. 1) and renal excretion of purine derivatives (357.6 +/- 90.7 mg purine-N x d(-1)) (Exps. 2 and 3) were not affected, indicating additional N supplementation did not improve rumen microbial growth. However, some deficiency of rumen degradable N might occur in non supplemented diets as suggested by the reduced rumen NH3-N and RNA concentrations (868 +/- 270 vs. 1466 +/- 466 mg RNA x kg(-1) rumen contents).
authors.affiliation: Department of Animal Production, Faculty of Agricultural and Applied Biological Sciences, Ghent University, Melle, Belgium. veerle.fievez@rug.ac.be
authors.forename: V
authors.initials: V
authors.lastname: Fievez
authors.forename: K
authors.initials: K
authors.lastname: De Fauw
authors.forename: K
authors.initials: K
authors.lastname: Notteboom
authors.forename: D
authors.initials: D
authors.lastname: Demeyer
mesh_terms: D000818:Animals; D000833:Animals, Suckling; D002417:Cattle / Q000378:metabolism*; D004044:Dietary Proteins; D005260:Female; D009584:Nitrogen / Q000378:metabolism*; D012417:Rumen / Q000378:metabolism* / Q000382:microbiology*; D012820:Silage; D014508:Urea / Q000097:blood / Q000652:urine; D003313:Zea mays / Q000378:metabolism*
chemical_list: D004044:Dietary Proteins; D014508:Urea; D009584:Nitrogen