I've been doing a lot of research on animal colors and the genetics behind them and sadly found that many white colors are linked to health issues. I love the color white in animals, and not all of them are, but I just thought I would share why the color white can lead to behavior, immune system, and physical health complications.
Melanin is not only the pigment that colors mammals, it is used for more then just make a dog black, brown, tan or blue. Melanin is very important in helping us regulate UV light from the sun and responds to more time in the sunlight by tanning (or freckling).
Melanin helps to protect or eyes so that when we look at bright objects they are not injured (well, really bright things can still be bad).
As a matter of fact, in wild cats melanin has been linked with better immune system functions and immunity towards certain viruses and many cat populations, particulalry in forests (where they better blend in) or on cold mountain tops (where the dark color absorbs the suns warmth) are melanistic.
Melanin helps to absorb the warmth of the sun and so can assist creatures like reptiles in thermoregulation. Some species will darken in color while basking and lighten when cool enough to help regulate their temperature.
In Vertebrates, melanin is synthesized from the amino-acid tyrosine in vesicular organelles (melanosomes) of neural-crest derived cells called melanophores (or melanocytes). These interact with the endocrine, immune and nervous system.
For this reason, melanin is linked with many of the highly important functions of the brain and body and without its production or when its production is altered it can lead to more then a simple change in skin, fur, feather, scale, or eye color. It can also lead to changes in behavior and health.
For example, without melanin in the skin thermoregulation, UV filtering and cancer protection is cut down, which can lead to issues in creatures that spend time in the sunlight. Wild animals also are prone to predation, but as pets this is not a problem.
Without melanin in the eyes then the retinofugal optic fibers are misrouted and can lead to crossed eyes (as seen in Siamese cats). Any bright lighting leads to pain in the sensitive eyes and visual acuity is decreased due to light scattering with-in the eye. Sight is also reduced due to foveal hypoplasia and possible light-induced retinal damage.
Nystagmus (irregular rapid movement of the eye) can be seen in albinos, Amblyopia (trouble seeing because of poor transmission to the brain), and optic nerve hypoplasia (underdevelopment of the optic nerve).
Melanocytes are found in the central nervous system, including areas of the brain responisble for mood and responses to stress. Albino or white animals often have behaviors changes with coloration changes. Small amounts of white are linked to calmer, tamer species (which is why many animals selected for tame behavior will often developed piebalding). However, large amounts of white (as soon in some pinto horses and dalmatian dogs) is linked with stress, nervousness and aggression.
Melanocytes are found in the inner ear and impaired migration of these melanocyes can lead to deafness in many white animals in one or both ears (to vary degrees). Blue-eyed White Cats, white-faced ferrets, many pied dogs (including dalmations) all have a risk of being born deaf.
There is also a risk of abnormalities in the skull and body shape its self, as seen in wardy ferrets. There may be problems with balance and coordination because of the misformed brain.
Some forms of white can also be lethal (known as Lethal White). While it isn't technically deadly, when two merle dogs are bred together their puppies are often blind and deaf and many breeders will put them down at birth. This is called Double Merle.
Lethal White foals will usually die soon after birth and are produced in Pinto horses when a foal as has too much white on them.
Lethal forms of spotting are seen in Gerbils, Mice, Rats, Dwarf Hamsters, and Syrian Hamsters and if two copies of said gene are put together then the babies are likely to die or be born without eyes.
No animal should have to live with sight, hearing, or brain issues because the wonder of being able to hear is what lets an animal enjoy life to its fullest. I hope to continue my studies and find the best ways to keep animals healthy and still allow for the wonderful variety of colors and breeds seen today. However, if some colors must be stopped for health reasons, I believe it should be done. Many people are against the breeding of Double Merles, wardy ferrets and other such animals for this reason.
Thanks for reading this long post. : )