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How to spot signs of nutritional deficiency in cats
Search for missing patches of fur.
Look over your cat for signs of missing fur. One of the first symptoms of malnutrition in cats is loss of fur, so bald spots signal that your cat may be missing something from its diet.
If you've found a stray cat or adopted a cat, also check for dark fur patches. When a cat loses fur due to nutritional deficiency, it grows back darker.