title: Monensin and ammoniation or urea supplementation of bermudagrass hay diets for steers.
abstract: One growth trial using crossbred beef steers (297 +/- 2 kg, Exp. 1) and one metabolism trial using Holstein steers (405 +/- 14 kg, Exp. 2) were conducted to evaluate effects of ammoniation (3% of hay DM, added as anhydrous NH3) vs urea supplementation with or without monensin supplementation of mature 'Alicia' bermudagrass hay-based diets for steers. Ammoniation (P < .05), but not urea (P = .26) or monensin (P = .70) supplementation, increased ADG in Exp. 1. In Exp. 2 ammoniation increased hay DMI (P < .05), but urea (P = .88) or monensin (P = .16) had no effect. Supplementation with either monensin (P < .05) or urea (P < .05) decreased ruminal total VFA concentrations. Monensin also decreased the ruminal acetate:propionate ratio (P < .001) and increased ruminal pH (P < .05). Addition of urea to the concentrate supplement decreased the rate of concentrate intake. Both the rate (P < .05) and the potential extent (P < .001) of ruminal forage in situ DM and NDF disappearance were increased by ammonia treatment. Dietary interactions (P < .10) were detected between monensin and ammoniation for rate and potential extent of in situ NDF disappearance and between monensin and urea supplementation (P < .05) for ruminal total free amino acid concentrations. Decreased concentrations of VFA and lower forage digestibilities observed with monensin supplementation in Exp. 2 may explain the failure of monensin to affect ADG in Exp. 1.
authors.affiliation: Department of Animal Science, Louisiana State University Agricultural Center, Baton Rouge 70803, USA.
authors.forename: D B
authors.initials: DB
authors.lastname: Vagnoni
authors.forename: W M
authors.initials: WM
authors.lastname: Craig
authors.forename: R N
authors.initials: RN
authors.lastname: Gates
authors.forename: W E
authors.initials: WE
authors.lastname: Wyatt
authors.forename: L L
authors.initials: LL
authors.lastname: Southern
mesh_terms: D000641:Ammonia / Q000494:pharmacology*; D000821:Animal Feed / Q000592:standards*; D000818:Animals; D002417:Cattle / Q000254:growth & development* / Q000502:physiology; D004435:Eating / Q000187:drug effects / Q000502:physiology; D005232:Fatty Acids, Volatile / Q000032:analysis; D005527:Food, Fortified; D006863:Hydrogen-Ion Concentration; D008297:Male; D008985:Monensin / Q000494:pharmacology*; D009584:Nitrogen / Q000032:analysis; D006109:Poaceae; D012417:Rumen / Q000737:chemistry / Q000187:drug effects / Q000502:physiology; D013997:Time Factors; D014508:Urea / Q000494:pharmacology*; D015430:Weight Gain / Q000187:drug effects / Q000502:physiology
chemical_list: D005232:Fatty Acids, Volatile; D000641:Ammonia; D014508:Urea; D008985:Monensin; D009584:Nitrogen