title: Ruminal ammonia load affects leucine utilization by growing steers.
abstract: Six ruminally cannulated Holstein steers (initial BW = 189 +/- 11 kg) housed in metabolism crates were used in a 6 x 6 Latin square to study effects of ruminal ammonia load on Leu utilization. All steers received a diet based on soybean hulls (2.7 kg of DM/d), ruminal infusions of 200 g of acetate/d, 200 g of propionate/d, and 50 g of butyrate/d, as well as an abomasal infusion of 300 g of glucose/d to provide energy without increasing microbial protein supply and an abomasal infusion of a mixture (238 g/d) of all essential AA except Leu. Treatments were arranged as a 3 x 2 factorial and included Leu (0, 4, or 8 g/d) infused abomasally and urea (0 or 80 g/d) infused ruminally. Abomasal Leu infusion linearly decreased (P < 0.05) both urinary and fecal N excretions and linearly increased (P < 0.05) retained N, but the decreases in urinary N excretion in response to Leu tended (P = 0.07) to be greater, and the increases in retained N in response to Leu were numerically greater in the presence of the urea infusion. Although urea infusions increased (P < 0.05) plasma urea concentrations, urinary N excretions, and urinary urea excretions, retained N also was increased (P < 0.05). The efficiency of deposition of supplemental Leu ranged from 24 to 43% when steers received 0 or 80 g of urea/d, respectively. Under our experimental conditions, increasing ammonia load improved whole-body protein deposition in growing steers when Leu supply was limiting.
authors.affiliation: Department of Animal Sciences and Industry, Kansas State University, Manhattan, 66506-1600, USA.
authors.forename: M S
authors.initials: MS
authors.lastname: Awawdeh
authors.forename: E C
authors.initials: EC
authors.lastname: Titgemeyer
authors.forename: K C
authors.initials: KC
authors.lastname: McCuistion
authors.forename: D P
authors.initials: DP
authors.lastname: Gnad
mesh_terms: D000018:Abomasum / Q000378:metabolism; D000641:Ammonia / Q000032:analysis / Q000378:metabolism*; D000821:Animal Feed / Q000032:analysis; D000818:Animals; D001786:Blood Glucose / Q000032:analysis / Q000187:drug effects; D002417:Cattle / Q000378:metabolism*; D019587:Dietary Supplements; D004063:Digestion / Q000187:drug effects / Q000502:physiology; D007328:Insulin / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000187:drug effects; D007930:Leucine / Q000378:metabolism* / Q000494:pharmacology; D008297:Male; D009584:Nitrogen / Q000032:analysis / Q000378:metabolism; D012417:Rumen / Q000378:metabolism*; D014508:Urea / Q000008:administration & dosage / Q000032:analysis / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D001786:Blood Glucose; D007328:Insulin; D007334:Insulin-Like Growth Factor I; D000641:Ammonia; D014508:Urea; D007930:Leucine; D009584:Nitrogen