| Popis: |
Two experiments were conducted using feeder calves in a randomized block design to determine the effects of organic and inorganic sources of Zn and Mn fed pre- and posttransit (Exp. 1 and 2) with or without injectable Cu (Exp. 2) on DMI, rectal temperature, BW changes, and plasma Zn and Cu concentrations of feedlot steers challenged with infectious bovine rhinotracheitis virus (IBRV). In Exp. 1, before weaning, all steers and their dams received the following free-choice mineral supplements: 1) control (no supplemental Zn or Mn), 2) ZnO+MnO (ZnMnO), and 3) Zn methionine+Mn methionine (ZnMnMet). In Exp. 2, 18 d before weaning and shipping, steers were allotted into two groups (22 steers/group) and fed 225 mg of Zn.steer-1 x d-1 in .9 kg of ground corn as ZnO or ZnMet. Half of the steers from each group were injected (s.c.) with 120 mg of Cu from Cu glycinate. Steers (Exp. 1 and 2) were weaned and shipped approximately 2,500 km to the feedlot, where they received the same supplements in the form of a complete diet for 34 d, during which time calves recovered from the stress due to shipment. All steers were initially sero-negative to IBRV. On d 34 (d 0 of IBRV), all steers were challenged with IBRV and DMI, rectal temperature, and BW change were monitored for 28 d.(ABSTRACT TRUNCATED AT 250 WORDS) |
