Researchers at the University of Kentucky have shown that high levels of supplemental zinc in nursery diets causes increases in fecal zinc (Zn) excretion.

Supplemental zinc oxide (ZnO) is often used to control diarrhea and promote growth in postweaning pigs. In this study, researchers examined the effect of this practice on waste management.

Eighteen barrows, averaging 16 lb. and 22 days of age, were used to evaluate three levels of supplemental Zn (0, 2,000 and 3,000 ppm) from ZnO on fecal excretion. All diets contained a basal level of 150 ppm zinc.

Pigs were fed complex phase I and phase II diets for the entire three-week study. Feed waste was collected daily, and feed intake and growth rate were determined weekly. Total fecal collection was performed for each weekly period.

There were no positive effects of zinc addition on growth rate. Pigs fed higher levels of zinc absorbed greater amounts of zinc, which was confirmed by liver mineral concentrations. The liver mineral concentrations also revealed a negative effect of the high zinc levels on absorption of other minerals, most notably copper.

Pigs fed the 2,000 and 3,000 ppm zinc diets excreted 14.1 and 21.7 times as much fecal zinc as the pigs fed the diet with a normal level of zinc supplementation. At the highest level of supplementation, the amount of zinc excreted just during this nursery period would exceed that of pigs fed a normal level of zinc during the entire grow-finish period.

In conclusion, researchers note that high zinc excretion suggests that the use of high levels of zinc supplementation should be restricted to as short a period as possible.

Researchers: Terry Meyer, Merlin Lindemann and Gary Cromwell, University of Kentucky. Phone Lindemann at (859) 257-7524, or e-mail him at