Black cats on diets deficient in phenylalanine + tyrosine, found that their lovely black coat colour changed to a reddish brown. This was caused by a reduction in the melanin (pigment) in the hair, a decreased total melanin concentrations of tyrosine in plasma. Reddish hair colour or rusting was induced in cats fed tyrosine deficient diets for 6 months and in black kittens born to queens that were given tyrosine-deficient diets during their pregnancy.
Quelle