Why Is My Black Cat Turning Brown?

My domestic shorthair cat has had a glossy black coat for 5 years and now parts of her coat have discolored to become a tan color. Why is this happening to my cat and how can I reverse it? (Shaun Avis - Australia)

Your cat's original coat color was determined by genetics, but gene action varies depending on the cellular resources available. What this means is that your cat's genes determine a black coat color, but that something physiological has changed which has resulted in a different effect of the gene action. Several academic studies have shown that a dietary deficiency of the amino acid Tyrosine result in a reddening of coat color in cats (Effect of low levels of dietary tyrosine on the hair color of cats, School of Veterinary Medicine, University of California). This dietary deficiency is associated with a reduction in melanin (the pigmentation) in hair. In albinos, melanin is absent completely - hence the lack of color. As an interesting side-note, part of the metabolic pathway involved in pigmentation is heat-sensitive, which is why Siamese cats get darker in winter!

It has been shown in the academic press (Red hair in black cats is reversed by addition of tyrosine to the diet, School of Veterinary Medicine, University of California), that increasing your cat's tyrosine intake can reverse the coat color changes. Supplements are available, but you should have your cat checked by your veterinarian for conditions that may make tyrosine supplementation dangerous (such as liver damage). In the first instance, start by feeding your cat foods which are naturally high in tyrosine, such as meat, eggs and milk. I don't have any estimate of how quickly the coat will regain its blackness, but the evidence shows that this is the best course of action.