title: Effects of ammonia load on methionine utilization by growing steers.
abstract: Seven ruminally cannulated Holstein steers (194 +/- 16 kg) housed in metabolism crates were used in a 6 x 6 Latin square, with one additional steer, to study effects of ruminal ammonia load on methionine (Met) use. All steers received a diet based on soybean hulls (2.6 kg DM/d), ruminal infusions of 200 g/d of acetate, 200 g/d of propionate, and 50 g/d of butyrate, as well as abomasal infusion of 300 g/d of glucose to provide energy without increasing microbial protein supply, and abomasal infusions of a mixture (248 g/d) of all essential AA except Met. Treatments were arranged as a 3 x 2 factorial and included urea (0, 40, or 80 g/d) infused ruminally to supply metabolic ammonia loads and Met (2 or 5 g/d) infused abomasally. Supplementation with the greater amount of Met decreased (P < 0.05) urinary N excretion from 68.8 to 64.8 g/d and increased (P < 0.05) retained N from 22.0 to 27.5 g/d. Urea infusions linearly increased (P < 0.05) urinary N excretions, plasma urea concentrations, and urinary urea excretions, but retained N was not affected. The efficiency of deposition of supplemental Met, calculated by assuming that Met deposition is 2.0% of protein deposition (6.25 x retained N), ranged between 18 and 27% when steers received 0 or 80 g/d of urea, respectively. There were no (P > or = 0.40) effects of treatments on serum insulin or IGF-I concentrations. In our model, increasing ammonia load did not affect whole-body protein deposition in growing steers when Met 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: D000641:Ammonia / Q000008:administration & dosage* / Q000378:metabolism / Q000494:pharmacology*; D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002417:Cattle / Q000254:growth & development* / Q000378:metabolism*; D008297:Male; D008715:Methionine / Q000378:metabolism*
chemical_list: D000641:Ammonia; D008715:Methionine