See thread on palatable copper and zinc. I have 3 horses, two of them PPID both coming 20 and both pintos, one is a sorrel and the other bay. I also have a black mustang coming 8. She is showing signs of a copper deficiency in that her coat is showing a coppery color in patches. This first showed up last summer. All the horses have basically the same diet and have been together for about 4 years. The black mustang and the bay pinto mare had a very deprived beginning as foals. I am assuming that the black pigmentation has a higher requirement of copper. Is this correct? 
How long does it take for a copper deficiency to show up by observation? Years?
How to determine if the two pintos are also suffering a copper deficiency by observation?
Do wild black mustangs mostly show signs of copper deficiency?
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- Frances C.
December 2017, Washington & California
Case history: https://ecir.groups.io/g/CaseHistory/files/Frances%20and%20Phoenix
Phoenix's Photo Album: https://ecir.groups.io/g/CaseHistory/album?id=12382