Online currently there is a GeoBeats story about an adorable cat called Pugsley who when adopted from a rescue center was orange. It was an extreme case of tyrosine deficiency due to him being on a very unbalanced diet for a long time before he entered the shelter (on my assessment). Normally black cats go a little rusty but sometimes you’ll see stories of rusty cats – or plain orange cats – going black. And it almost always down to their diet.

Melanin is derived from the amino acid—tyrosine—through a synthesis regulated by the enzyme tyrosinase. The final product results in a range of brown and black pigments that gives animal skin and hair its color (Lawrence, 2008a).

Science Direct

Yes, the aromatic amino acid called tyrosine which is automatically in well-made commercial cat food is needed in the diet to create melanin a black/brown pigment that colours the hair strands, creates eye colour and for instance those ‘freckles’ you see inside the mouth of some cats. Among the 20 standard amino acids, the following are classically considered aromatic: phenylalanine, tryptophan and tyrosine (Wikipedia)

If for some strange and normally careless reason a black cat turns orange in parts it will normally be linked to a poor diet which is deficient in tyrosine.

And just as melanin is reduced in the fur of black cats on a diet lacking tyrosine, this pigment can be added in by placing the cat on a good, healthy diet containing animal or plant protein. This supports the viability of a commercially prepared vegetarian cat food which is controversial but which is available today and, in my view, a good product.

This is what happened to Pugsley, the charming cat in the Geobeats story.

There is an inherited condition due to a genetic mutation that affects humans called: Tyrosine hydroxylase deficiency (THD) but I don’t think it affects cats.

It may be useful to look at the benefits of tyrosine for humans. For instance, the WebMD website says that “some studies show that tyrosine helps people function under stress and might improve memory during stressful situations. Tyrosine also might help you stay sharp if you have lost a lot of sleep.”

No one has asked if the same benefits are conferred on cats! I don’t know but it seems reasonable to suggest that if a black cat has turned rusty orange because of a lack of tyrosine they may also suffer from a predisposition to anxiety and lower cognitive abilities although that is entirely speculative.

Black cats on a good diet might look a little rusty red under certain light. For instance, when sunlight shines through the fur (backlit). This is all normal. The pigment granules in the hair strands are brown/black. They are not entirely opaque. When bright light impinges on the granules, they transmit some light which renders them a brownish colour which translates to seeing some rust in black cats sometimes.

If you black cat is on an excellent diet and looks inordinately rusty-red you should have a vet take a look as there may be an underlying health issue such as hyperthyroidism, kidney disease, and liver disease.

Here is Pugsley’s story:

Some pages on melanin:

Cats that change colour from orange to black and black to orange

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The making of white cat fur, blue eyes and deaf cats

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Feline ‘freckles’ (9 facts)

Read More

Is your black cat rusty red? Tyrosine deficient diet?

Read More

Cat hair pigmentation types (fully illustrated)

Read More

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