title: Daily and alternate day supplementation of urea or biuret to ruminants consuming low-quality forage: I. Effects on cow performance and the efficiency of nitrogen use in wethers.
abstract: Two experiments were conducted to determine the influence of supplemental nonprotein N (NPN) provided daily (D) or every other day (2D) on ruminant performance and N efficiency. Treatments included an unsupplemented control (CON) and a urea (28.7% CP) or biuret (28.6% CP) supplement provided D or 2D at 0700. In Exp. 1, five wethers (39 +/- 1 kg BW) were used in an incomplete 5 x 4 Latin square with four 24-d periods to determine the influence of supplemental NPN source and supplementation frequency (SF) on the efficiency of N use in lambs consuming low-quality grass straw (4% CP). The amount of CP supplied by each supplement was approximately 0.10% of BW/d (averaged over a 2-d period). In Exp. 2, 80 Angus x Hereford cows (540 +/- 8 kg BW) in the last third of gestation were used to determine the effect of NPN source and SF on cow performance. The NPN treatments were formulated to provide 90% of the estimated degradable intake protein requirement. The supplemented treatments received the same amount of supplemental N over a 2-d period; therefore, the 2D treatments received double the quantity of supplemental N on their respective supplementation day than the D treatments. In Exp. 1, total DM, OM, and N intake; DM, OM, and N digestibility; N balance; and digested N retained were greater (P < 0.03) for supplemented than for CON wethers, with no difference (P > 0.05) between NPN sources or SF. Plasma urea-N (PUN) was increased with N supplementation compared with CON (P < 0.01), and urea treatments had greater PUN than biuret (P < 0.01). In addition, PUN was greater (P = 0.02) for D than for 2D treatments. In Exp. 2, pre- and postcalving (within 14 d and 24 h after calving, respectively) cow weight and body condition score change were more positive (P < 0.05) for supplemented groups than for CON. These results suggest that supplements containing urea or biuret as the primary source of supplemental N can be effectively used by lambs and cows consuming low-quality forage, even when provided every other day.
authors.affiliation: Eastern Oregon Agricultural Research Center, Oregon State University, Burns 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: S J
authors.initials: SJ
authors.lastname: Bartle
mesh_terms: D000821:Animal Feed; D000818:Animals; D001737:Biuret / Q000008:administration & dosage* / Q000009:adverse effects; D002417:Cattle / Q000502:physiology*; D004044:Dietary Proteins / Q000378:metabolism*; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule / Q000662:veterinary; D005260:Female; D008297:Male; D009584:Nitrogen / Q000378:metabolism*; D009751:Nutritional Requirements; D011247:Pregnancy; D011897:Random Allocation; D012417:Rumen / Q000378:metabolism; D012756:Sheep / Q000378:metabolism*; D014508:Urea / Q000008:administration & dosage* / Q000009:adverse effects
chemical_list: D004044:Dietary Proteins; D001737:Biuret; D014508:Urea; D009584:Nitrogen