Journal of Animal Science, Vol 71, Issue 5 1281-1287, Copyright © 1993 by American Society of Animal Science

JOURNAL ARTICLE

Ruminal distribution of zinc in steers fed a polysaccharide-zinc complex or zinc oxide

D. W. Kennedy, W. M. Craig and L. L. Southern
Department of Animal Science, Louisiana State University Agricultural Center, Baton Rouge 70803.

Six Holstein steers (initial BW 335 kg) were used in a replicated 3 x 3 Latin square design to study the distribution of Zn in ruminal contents from a conventional Zn source (ZnO) or Zn sequestered to a polysaccharide (PC-Zn). Treatments consisted of a basal diet (no Zn supplementation) and the basal diet supplemented with Zn from either PC-Zn or ZnO. Steers were provided with 208, 920, or 896 mg of Zn/d from basal, PC-Zn, or ZnO, respectively. On collection day, steers were dosed with 800 mg of Zn from each Zn supplement and whole ruminal contents (WRC) were sampled at 1, 2, 4, 6, and 8 h postdosing. The cell-free (soluble) Zn concentrations in steers fed the PC-Zn or ZnO supplements decreased (P < .05) rapidly after dosing. Mean Zn concentrations of the cell-free fraction were considerably lower than either microbial or particle fractions of WRC. Compared with ZnO, the PC-Zn source resulted in higher (P < .05) cell-free Zn at 1 and 2 h after dosing and higher (P < .05) Zn concentrations (micrograms/gram of DM) in the fluid- and particle-associated microbial and particle fractions. Compared with basal, fluid-associated microbial DM concentration tended to be higher (P < .10) at 6 and 8 h with PC-Zn and ZnO. Results indicate a rapid disappearance of Zn from the soluble fraction and a high concentration of Zn in the DM of the microbial and particle fractions of WRC. Furthermore, PC-Zn resulted in higher levels of Zn in all fractions of WRC, and Zn supplementation tended to increase microbial DM production at later sampling times.