Journal of Animal Science, Vol 75, Issue 11 3074-3081, Copyright © 1997 by American Society of Animal Science

JOURNAL ARTICLE

Zinc repletion with organic or inorganic forms of zinc and protein turnover in marginally zinc-deficient calves

T. E. Engle, C. F. Nockels, C. V. Kimberling, D. L. Weaber and A. B. Johnson
Department of Animal Sciences, Colorado State University, Fort Collins 80523, USA.

We conducted two experiments using marginally Zn-deficient (-Zn) calves to determine which supplemental chemical form of Zn would most rapidly reverse certain Zn deficiency signs and to determine whether a change in protein turnover had occurred in Zn deficiency. In Exp. 1, 40 crossbred beef heifers were allocated by BW to four groups. The control group received 23 mg Zn/kg diet DM from ZnSO4 supplemented to the -Zn diet (17 mg Zn/kg diet DM). The three other groups received the -Zn diet. After 21 d, based on a decreased (P < .05) feed efficiency, they were deemed -Zn. Cell-mediated immune (CMI) response to phytohemagglutinin (PHA) was reduced (P < .05) but plasma and liver Zn were unaffected in the -Zn calves. Zinc was repleted by feeding iso-Zn amounts (23 mg Zn/kg diet DM) from Zn lysine, Zn methionine, or ZnSO4. At 8 h after injection of PHA, control CMI response values were similar to Zn Methionine, and Zn lysine was lower (P < .05). In Exp. 2, 10 Holstein steers were allocated by BW to two groups. One group received the -Zn diet, and the other received the +Zn diet. Urine collections were obtained from both groups of calves when the -Zn calves showed a decrease (P < .05) in feed efficiency relative to the controls and when they were repleted with 23 mg Zn/kg diet DM from ZnSO4 and their feed efficiency had returned to that of the controls. Urinary 3-methylhistidine indicated that -Zn calves had less (P < .05) daily protein degradation than the controls. Refeeding Zn to the -Zn group did not change BW or daily protein degradation. Results indicated that a marginal Zn deficiency decreased fractional accretion rate, increased (P < .05) urine excretion, and tended to increase (P < .19) Na and decrease (P < .12) K concentrations in the urine.

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