Pigs were fed one of four dietary additions of a mixture of trace minerals (copper, iodine, iron, manganese, and zinc). Each incremental addition was formulated to supply 100% of the NRC (1998) estimated trace mineral needs for 5- to 10- kg pigs. In two separate trials, a total of 28 sets of four littermate pigs from a high lean strain were used to determine the effects of trace mineral additions on growth and efficiency of feed utilization. Additionally, these pigs were placed in the barn in such a manner that each of 14 pens of pigs receiving the same dietary treatment were placed over a common excreta pit. Excreta output was collected and weighed each week for a period of 4 weeks resulting in eight replications/trt for the mineral excretion data. Pigs were self-fed the basal diet for 10 days postweaning and then allotted within litter to one of four dietary additions of trace minerals.

In the current experiment, dietary trace mineral additions did not alter growth or efficiency of feed utilization. As dietary trace mineral concentration increased, the excretion (mg/kg of excreta and mg/pig/day) of Cu, Fe, Mn, and Zn increased linearly. Retention of these minerals also increased linearly as dietary trace mineral concentration increased, but the efficiency of retention was not altered except for Fe. When expressing the excretion of these trace minerals relative to P output there also was a linear increase in output.

Based on these data, increasing the dietary concentration of trace minerals above that required to support maximal growth results in greater environmental output. In addition, the ratio of these particular trace minerals to P in pig excreta is not constant but can be altered by dietary regimen.