To solve dull coat problems, some people suggest adding natural ingredients such as calf's liver, lanolin, egg yolk, fumitory, meadowsweet, sarsaparilla, burdock, echinacea, fish oil, brewer's yeast, olive oil, silicon, elderberry, etc., to the food or directly to the coat of our pet.
Personally, I prefer to use patented and tested professional formulas that contain essential fatty acids, Omega 3 and 6 as well as collagen. These supplements can simply be added to either feed or pate and the results on the coat are guaranteed.
My favorites are the following ones from Zanimo: