title: Effects of nitrogen fertilization and dried distillers grains supplementation: nitrogen use efficiency.
abstract: In a 3-yr study, 135 crossbred steers (330 ± 10 kg) were used in a randomized complete block design to evaluate corn dried distillers grains plus solubles (DDGS) fed to yearling steers as a substitute for forage and N fertilizer and its effect on N use efficiency in yearling steers grazing smooth bromegrass pastures. Steers were initially stocked at 6.8 animal unit months (AUM)/ha on nonfertilized smooth bromegrass pastures (CONT), at 9.9 AUM/ha on smooth bromegrass pastures fertilized with 90 kg of N/ha (FERT), or at 9.9 AUM/ha on nonfertilized smooth bromegrass pastures with 2.3 kg (DM) of DDGS supplemented daily per steer (SUPP). Paddock was the experimental unit, with 3 replications per treatment per year for 3 yr. Paddocks were strip-grazed, and put-and-take cattle were used to maintain similar grazing pressure among treatment paddocks during the 160-d grazing season. Steers consumed less forage (P < 0.01), but total N intake for SUPP was greater (P < 0.01) per steer and per hectare than for FERT, and both were greater (P < 0.01) than for CONT. Nitrogen retention for steers in the SUPP treatment was increased (P < 0.01) by 31% compared with N retention in the CONT and FERT treatments. Nitrogen retention per hectare for SUPP was 30 and 98% greater (P < 0.01) than N retention per hectare for FERT and CONT, respectively. Nitrogen excretion per steer and per hectare were also greater (P < 0.01) for SUPP than FERT, and both were increased (P < 0.01) compared with CONT. Animal N use efficiency was similar (P = 0.29) for steers in the CONT, FERT, and SUPP treatments. However, system-based N use improved (P < 0.01) by 144% for SUPP compared with FERT. The DDGS increased N intake and N excretion in yearling steers. However, because of improvements in BW gain and increases in stocking rate of pastures, DDGS can be a useful tool to increase the efficiency of N use in smooth bromegrass grazing systems.
authors.affiliation: Animal Science Department, University of Nebraska, Lincoln 68583-0908, USA.
authors.forename: M A
authors.initials: MA
authors.lastname: Greenquist
authors.forename: A K
authors.initials: AK
authors.lastname: Schwarz
authors.forename: T J
authors.initials: TJ
authors.lastname: Klopfenstein
authors.forename: W H
authors.initials: WH
authors.lastname: Schacht
authors.forename: G E
authors.initials: GE
authors.lastname: Erickson
authors.forename: K J
authors.initials: KJ
authors.lastname: Vander Pol
authors.forename: M K
authors.initials: MK
authors.lastname: Luebbe
authors.forename: K R
authors.initials: KR
authors.lastname: Brink
authors.forename: L B
authors.initials: LB
authors.lastname: Baleseng
mesh_terms: D000821:Animal Feed; D000822:Animal Husbandry; D000818:Animals; D031724:Bromus / Q000254:growth & development; D002417:Cattle / Q000254:growth & development / Q000502:physiology*; D004032:Diet / Q000662:veterinary; D019587:Dietary Supplements; D002523:Edible Grain; D005308:Fertilizers; D008297:Male; D009584:Nitrogen / Q000378:metabolism*; D015430:Weight Gain / Q000502:physiology; D003313:Zea mays
chemical_list: D005308:Fertilizers; D009584:Nitrogen