title: Cats require more dietary phenylalanine or tyrosine for melanin deposition in hair than for maximal growth.
abstract: In 1986, the NRC recommended a dietary concentration of 4.0 g/kg of phenylalanine and 8.5 g/kg of total aromatic amino acids for growing kittens on the basis of maximal growth rate and nitrogen balance. Black hair-coated cats were given purified diets containing the following phenylalanine + tyrosine (Phe + Tyr) concentrations (g/kg diet): 4 + 2, 4 + 4, 4 + 6, 4 + 8, 10 + 0, 10 + 2, 10 + 4, 10 + 6, 10 + 8, 10 + 10, 24 + 0 for at least 6 mo. All other amino acids were present at about twice the requirements. Total melanin and the oxidation product of eumelanin, pyrrole-2,3,5-tricarboxylic acid (PTCA) were measured in hair. There was a significant linear relationship between the concentrations of tyrosine in plasma and PTCA in hair. The relationship between PTCA concentration in hair and Phe + Tyr in the diet had a point of inflection at approximately 16 g/kg Phe + Tyr. Cats fed diets with <16 g Phe + Tyr developed "red hair." We confirmed the anecdotal reports that the black hair of cats can change from black to reddish brown. An aromatic amino acid concentration > or =18 g/kg is recommended for the prevention of visually discernible red hair in black-coated cats. Dietary concentrations >18 g total aromatic amino acids/kg diet promote a greater ratio of PTCA:total melanin in hair. We are unaware of a secondary nutrient requirement being so much greater than the requirement for growth.
authors.affiliation: Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, USA.
authors.forename: Peter J B
authors.initials: PJ
authors.lastname: Anderson
authors.forename: Quinton R
authors.initials: QR
authors.lastname: Rogers
authors.forename: James G
authors.initials: JG
authors.lastname: Morris
mesh_terms: D000818:Animals; D002415:Cats; D004032:Diet; D004305:Dose-Response Relationship, Drug; D006197:Hair / Q000378:metabolism*; D006200:Hair Color / Q000187:drug effects / Q000502:physiology*; D008543:Melanins / Q000378:metabolism*; D009751:Nutritional Requirements; D009994:Osmolar Concentration; D010649:Phenylalanine / Q000008:administration & dosage* / Q000494:pharmacology; D011758:Pyrroles / Q000378:metabolism; D014443:Tyrosine / Q000008:administration & dosage* / Q000097:blood / Q000494:pharmacology
chemical_list: D008543:Melanins; D011758:Pyrroles; D014443:Tyrosine; D010649:Phenylalanine; C071226:pyrrole-2,3,5-tricarboxylic acid