First of all: There can be various reasons why a dog has bad fur. Diseases, too much UV radiation and wrong dog nutrition or nutrient deficiency are the main factors. Fur changes are also due to age and season.
High quality proteins for shiny and beautiful fur
Basically, your dog should be balanced and fed with the best quality. Ready-made feed cannot always meet these requirements, and mistakes can also occur when bartending. If in doubt, discuss the choice of the right food with your veterinarian, especially if your dog has dull fur despite grooming or appears sickly overall.
So that your pet gets the necessary shine on the fur, you should make sure that it gets enough digestible protein such as muscle meat to eat in sufficient quantities. Dog fur is partly made of protein. It is therefore important that high-quality protein is ingested in the dog food.
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Essential amino and fatty acids ensure a healthy shine
You can also supplement dog food with unsaturated fatty acids - ideally with high-quality oils such as fish or linseed oil. Linoleic acid can also be a gloss accelerator for fur. However, oil should only be added in moderation; Your veterinarian will be happy to advise you.
Vitamins, especially A and B vitamins as well as minerals such as zinc also play a crucial role in terms of coat quality. All nutrients must be ingested through dog nutrition, since the body cannot form them on its own - don't save at the wrong end here.