At birth, most kittens are born with the coat colour they will keep for life, but there are some exceptions to this rule. Colour changes can occur for a variety of reasons including nutritional deficiencies, genetics, autoimmune disorders and the natural ageing process in middle-aged to senior cats.
Himalayan gene
Pointed cats such as the Siamese, Birman and Ragdoll carry two copies of the Himalayan gene, that inhibit the development of pigmentation on the fur above 100 – 102 F (37.7 – 38.8). The coat colour genes turn on in cooler parts of the body such as the face, lower limbs and tail, but warmer parts remain pale due to a lack of pigmentation. Kittens who carry the Himalayan gene are born all white because the warmth of the womb blocks the cat’s colour gene. Over time, the pointed pattern develops on cooler parts of the body such as the face, legs, ears and tail.
Pointed cats may also develop darker fur, particularly on their body, in winter due to the cooler temperature, and as the weather warms up, their coat becomes paler again. The coat of a pointed cat typically becomes darker in winter due to the cooler temperatures. Interestingly, if a pointed cat has worn a bandage for an extended period, the fur beneath it will be paler due to the increased warmth.
Black coat turning red
Some black cats may develop a rusty red hue which is most apparent in sunlight due to a deficiency in tyrosine, due to a reduction of melanin in the hair shaft. Tyrosine is a non-essential amino acid that the body produces from another amino acid called phenylalanine. Tyrosinase is necessary to make melanin, the pigment which gives hair its colour.
Researchers conducted experiments on black cats who were fed tyrosine-deficient diets for six months which resulted in the fur changing from black to reddish brown (known as rusting) due to a reduction of the pigment melanin in the hair shaft. Tests revealed reduced levels of total melanin concentrations as well as low concentrations of tyrosine in plasma. Cats fed a diet with high concentrations of tyrosine or phenylalanine were able to reverse redness in black cats.
Copper deficiency and zinc excess can also cause rusting as copper helps tyrosine as a pigment factor and excess zinc can cause copper deficiency. Feeding a complete and balanced cat food can should prevent rusting in cats, however, if it does develop, please do not suppliment your cat’s diet without speaking to a veterinarian as cats have very specific nutritional.
Ghost tabby markings
Genetically, all cats are tabbies, however, some genes mask the tabby pattern, giving the appearance of a solid-coloured cat. Ghost tabby markings refer to a faint tabby pattern seen most commonly on black kittens, which eventually disappear as the kitten reaches adulthood. It may be possible to see these markings in bright light. The image above shows a black kitten with mackerel tabby stripes along the flanks and legs.
Fever coat
Fever coat is a rare phenomenon where kittens are born with a smokey grey coat. It is thought to be a response to maternal fever during pregnancy which exposes the unborn kittens to an elevated body temperature. The coat of affected kittens has dark roots, with silver/grey tips, but are otherwise well. As the kitten grows, the unusual fever coat colour is replaced with the cat’s natural coat colour.
Vitiligo
Vitiligo is an extremely rare condition in cats caused by the destruction of pigment-producing cells (melanocytes) resulting in areas of depigmentation that may be confined to one small patch or throughout the body. Unfortunately, there is little research into the underlying cause of vitiligo in cats, but human studies indicate the most likely causes to be genetic predisposition and immune-mediated. Immunosuppressive therapy is used in humans with vitiligo but is generally not recommended in cats as vitiligo is cosmetic only and the side effects outweigh the benefits.
Ageing
White hairs may develop on cats as they age. Greying isn’t as widespread in cats as it is in dogs and humans, but pet owners may notice a sprinkling of white hairs in the coat of older cats. Melanocytes are specialised cells located in the hair follicle which produce melanin, the pigment responsible for hair colour. As the cat ages, some melanocytes gradually die, and the missing melanin granules are replaced by air pockets in the hair shaft.
When to seek help
If you notice any changes to a cat’s coat colour, speak to a veterinarian to determine the cause. This is especially important if the colour changes have happened rapidly, and/or the cat is also experiencing additional symptoms. Most cases of coat colour changes are harmless, but as there are some medical causes, it is always safest to have it checked out.