[ally173]

my dog's vet is recommending the purina EN wet formula. however i noticed the following ingredients which can be toxic, especially for a dog with IBD and digestive issues.
Copper sulfate, menadione sodium bisulfite complex and sodium selenite; these ingredients can be toxic and cause vomiting and are not meant for long term use. however the vet said she might be on this diet for a long term if not her life.
can anyone please tell me more about these ingredients, why are they added to this formula and how safe are they? thanks