Tyrosine and phenylalanine
The colour of the coat depends on the presence of pheomelanin grains (yellow to red pigments) and eumelanin grains (brown to black).The production of these pigments requires the presence of tyrosine and phenylalanine, two aromatic amino acids (so-termed because of their ring structure).
A default in the animal’s intake in dark or black subjects provokes a reddening of the hair, which has already been shown in cats. Studies on Newfoundland and black Labrador puppies show that the phenylalanine and tyrosine levels needed for optimal coat pigmentation are twice that of the corresponding growth-related requirements. Tyrosine supplementation even helps increase the intensity of hair coloration.
A little background information
The Siamese cat’s particular colour (" colourpoint") is due to properties of tyrosinase, the key enzyme in melanin production. In this breed, the enzyme works only at a relatively low temperature. Warmer areas like the flanks, the belly and the back remain clear, while colder areas like the head, feet and tail are coloured.
Their role in the body
Besides its role in hair and iris pigmentation, tyrosine is also a dopamine, noradrenalin and adrenalin precursor. These molecules are involved in the proper functioning of the brain and in the reproductive function. Tyrosine supplementation therefore has a positive effect on fertility.
Natural sources
Tyrosine is either provided directly in the diet or synthesised from phenylalanine, an essential amino acid. Milk and dairy products are excellent sources of tyrosine. Rice is the only vegetable source to contain non-negligible quantities of this amino acid.
