title: Investigations of the influence of the content of plant crude protein in the ration on the utilisation of urea in dairy cattle. 5. 15N-fractions in the blood of lactating cows given 15N-urea intraruminantly.
abstract: The incorporation of urea-15N (given as an intraruminal drench or infusion) into plasma urea and protein of dairy cows fed isoenergetic rations with different levels of plant protein (9, 11, 12, 14, 15 and 17% in DM) was investigated. A nonlinear and asymptotic dependence between the plasma concentration of urea and protein level in the ration was stated. The availability of dietary urea-15N for plasma urea for 48 hours after administration was lowest in cows fed with low protein rations (9 and 11% of plant protein). On the contrary the highest incorporation of urea-15N into plasma protein of these animals was observed. The possible explanation of these results is presented.
mesh_terms: D000818:Animals; D002417:Cattle / Q000378:metabolism*; D004044:Dietary Proteins / Q000008:administration & dosage*; D005260:Female; D007774:Lactation; D009587:Nitrogen Isotopes; D010940:Plant Proteins / Q000008:administration & dosage*; D011247:Pregnancy; D012417:Rumen; D014508:Urea / Q000008:administration & dosage / Q000097:blood / Q000378:metabolism*
chemical_list: D004044:Dietary Proteins; D009587:Nitrogen Isotopes; D010940:Plant Proteins; D014508:Urea