Supplemental zinc should be supplied in the mineral mix. Good sources include zinc sulfate, zinc oxide, zinc chelates, and zinc chloride. Zinc is found in most trace-mineralized salt products commercially available. Copper is essential for proper enzyme function and maintenance of elastic connective tissue. Copper sulfate is a common supplement source for horses.
Grains can be a significant source of copper.
Our feed tag doesn't list the amount of copper, but the amount available will probably meet our requirements. If you want to increase the copper level, a trace-mineralized salt for horses is available through feed companies such as Buckeye Feeds, Land of Lakes, and others. Manganese is necessary for cartilage formation. Our forage provides adequate amounts if that's all we fed. The concentration in our feed will likely meet our requirement.