Most sheep will die within 2 to 4 days after blood concentrations sky rocket. Because of the variation in recommended copper concentrations, it is difficult to have one copper level in a trace mineralized salt for all species. This would insure that all species would receive an appropriate amount of copper without the risk of copper toxicity in sheep. Those swine producers feeding copper as a growth promotant will continue to supplement copper in addition to that in the trace mineralized salt. Copper Source Knowing the copper concentration in a diet without knowing the source of supplemental copper is of little nutritional value.
Grains are lower in copper than are forages.
Most forages will contain copper at levels equal to or above the NRC requirement for ruminants. However, as plants mature and the phytate and lignin content increases, bioavailability of the copper decreases rapidly. Copper oxide and copper sulfate have been the two predominant sources of supplemental copper used in animal feeds. In the last ten years there has been considerable research comparing the bioavailability of these and other copper sources in the different species. In 1987 Ledoux et al.