title: Daily and alternate-day supplementation of urea or biuret to ruminants consuming low-quality forage: II. Effects on site of digestion and microbial efficiency in steers.
abstract: Five steers (491 +/- 21 kg BW) were used in an incomplete 5 x 4 Latin square with four 24-d periods to determine the influence of supplemental non-protein N (NPN) source and supplementation frequency (SF) on nutrient intake and site of digestion in steers consuming low-quality grass straw (4% CP). Treatments (TRT) included an unsupplemented control and a urea- or biuret-containing supplement placed directly into the rumen daily (D) or every other day (2D) at 0700. The NPN treatments were formulated to provide 90% of the estimated degradable intake protein requirement. Daily TRT were supplemented CP at 0.04% of BW/d, whereas the 2D TRT were supplemented at 0.08% of BW every other day. Therefore, all supplemented TRT received the same quantity of supplemental CP over a 2-d period. Forage OM intake was not affected (P > 0.05) by NPN supplementation, NPN source, or SF; however, total OM and N intake were increased (P < 0.01) with CP supplementation. Duodenal flow of N was greater (P = 0.04) with CP supplementation compared with the control. In addition, duodenal bacterial N flow was increased with CP supplementation (P = 0.04) and for biuret compared with urea (P < 0.01). Bacterial efficiency (g bacterial N/kg OM truly digested in the rumen) was greater (P = 0.05) for biuret than for urea. Apparent total-tract N digestibility was increased with NPN supplementation (P < 0.01) but not affected by NPN source or SF. These results suggest that urea or biuret can be used effectively as a supplemental N source by steers consuming low-quality forage.
authors.affiliation: Eastern Oregon Agricultural Research Center, Oregon State University, Burns, OR 97720, USA.
authors.forename: T A
authors.initials: TA
authors.lastname: Currier
authors.forename: D W
authors.initials: DW
authors.lastname: Bohnert
authors.forename: S J
authors.initials: SJ
authors.lastname: Falck
authors.forename: C S
authors.initials: CS
authors.lastname: Schauer
authors.forename: S J
authors.initials: SJ
authors.lastname: Bartle
mesh_terms: D000821:Animal Feed / Q000592:standards; D000818:Animals; D001419:Bacteria / Q000378:metabolism*; D001737:Biuret / Q000008:administration & dosage*; D002417:Cattle / Q000378:metabolism*; D019587:Dietary Supplements; D004063:Digestion; D004334:Drug Administration Schedule / Q000662:veterinary; D008297:Male; D009584:Nitrogen / Q000378:metabolism; D009751:Nutritional Requirements; D011897:Random Allocation; D012417:Rumen / Q000378:metabolism* / Q000382:microbiology; D014508:Urea / Q000008:administration & dosage*
chemical_list: D001737:Biuret; D014508:Urea; D009584:Nitrogen