Increased dietary intake of tyrosine upregulates melanin deposition in the hair of adult black-coated dogs.

The principle determinant of melanin derived hair colour and patterning in mammals is genetic, but environmental factors are now thought to play a role. It has been shown that the concentration of melanins in cat hair is influenced by the amino acid composition of their diets. Also, puppies were found to require tyrosine (Tyr) intake significantly greater than that recommended for normal growth and development in order to optimize melanin expression in their coats.