A LOT depends on where you live, and therefore what minerals/trace elements you have in your soil and water. And a lot depends on what kind of sheep you have. Icelandics for example, as well as some other northern short-tail/primitive breeds seem to require more copper than is usually provided by standard sheep minerals. In fact, the sheep mineral mixes I can get around here don't have ANY added copper, and one (Dumor) says right on the bag that they add extra Molybdenum to bind up any copper that might be in the sheep's diet, though they don't tell you how much Mo they are adding. Well, thanks, but that's not doing me any favors. I have to add either cattle or goat minerals to get the copper level up enough, or occasionally feed some goat pellets.
Sheep DO need copper. They just don't need a lot compared to other livestock, or maybe it's more precise to say that they cannot handle a lot of copper like other livestock can. They store excess in their liver, and then if a sudden stressor comes along (like being chased by a dog or something) the liver dumps all that copper into the bloodstream and... dead sheep.
But there are so many interactions between Cu and other metals/minerals that it's important to know what you have before you can make informed decisions. If you butcher an animal, you can send a liver sample for testing to find out the level of Cu present (and other elements). You can have soil tests done, as well as testing your hay, and your water. I know someone who has to add quite a bit of Cu to her mineral mixes to overcome the high levels of Mo and other things that are present in her soil and water. Otherwise, her sheep and other livestock get badly Cu deficient. But that's the situation where she lives. Someone else's might be quite different.
Pat Coleby's mineral mix is dependent on the idea that the sheep won't take in what they don't need. And if they do need Cu, they'll eat some. (Doesn't she recommend putting out the components individually, rather than mixed together?)
