Risk Factors

The skin is a major organ with many different functions. Obviously, it is important for social interactions, giving each individual its characteristic appearance. It also serves as a barrier to maintain a stable internal environment. The skin plays a major role in the immune response to external factors, but also has a distinctive role in metabolism, sensory perception and temperature regulation amongst others. An imbalanced intake of nutrients such as amino acids, fatty acids, vitamins or trace elements disrupts the barrier function and the immune protection provided by the skin. The cat may become more sensitive to infection and may develop allergic reactions more easily. Skin and coat are a mirror of a cat’s health and the quality of its food. Nutrition has a special place in feline dermatology, not only as an essential factor in the prevention of skin diseases, but also as a therapy for allergies and metabolic dermatopathies.

Ralf S. MUELLER
DMV, PhD, Dipl. ACVD, FACVSc, Dipl. ECVD

Ralf Mueller graduated in Munich, Germany in 1985, and worked in several large and small animal practices before completing a residency in veterinary dermatology at the University of California, Davis in 1992. In 1992 he moved to Melbourne, Australia where together with his partner and wife Dr. Sonya Bettenay he was director in a veterinary dermatology specialist practice and consultant at the University of Sydney. In 1999, he became Assistant Professor in Veterinary Dermatology at the College of Veterinary Medicine and Biomedical Sciences, Colorado State University and finished his habilitation thesis at Zurich University, Switzerland. In 2004, he accepted a position as chief of the veterinary dermatology service at the University of Munich, Germany. He has published over 80 studies, articles, book chapters and books.

Fabienne DETHIOUX
DVM, MRCVS

Fabienne Dethioux qualified as DVM in 1983 in Belgium, her native country (Université de Liège). In 1984, she started her own practice in Brittany where she stayed 12 years. In 1996, she moved to England and became Clinical Director for a corporate practice. She then worked as a free-lance consultant whilst being an emergency veterinarian in an animal hospital near Windsor. Since 1991, she is also a journalist and writes for several veterinary newspapers both in France and the United Kingdom. She has translated many articles, books and CD-roms. In 2003, she joined the Scientific communication department of Royal Canin. She now works with the International Division of the Group. Her main interest is dermatology.

1. Risk Factors

Breed Specificities

In contrast to dogs where several skin conditions can be directly related to nutrition, there is little evidence of a link between a breed, nutrient and a specific disease in the feline literature. However, the Siamese seems to have an increased tendency to food allergy (see section on "Dietary hypersensitivities").

Color of the Coat

The color of a cat is a complex feature and influenced by genetics, environment (temperature, UV intensity and humidity all alter the coat’s color by degrading the pigmentation) and nutrition (many nutrients play a role in pigment production).

The selection of colors in pure breed cats has become a specialist’s hobby. Pigmentation is linked to the distribution of melanin in the hair shaft. Eumelanin (black to brown) and pheomelanin (red to yellow) combine to form the various shades of a cat’s coat. The likelihood to produce eumelanin or pheomelanin is genetically determined but the enzyme which catalyzes the conversion from tyrosine can be a limiting factor.

Pigment synthesis in the melanocytes depends on the supply of specific amino acids:

- Phenylalanine and tyrosine are melanin precursors (Figure 1)
- Cysteine is needed for the production of pheomelanin. It contains a high proportion of sulphur.

A dietary deficiency in tyrosine (or its precursor, phenylalanine) has been shown to induce a reddish change in the black hair of cats (Figure 2). Similarly the deep orange colored cats turned pale orange when experimentally fed a diet lacking tyrosine (Yu et al., 2001).

According to the National Research Council (NRC) 2006, the adequate intake for an adult cat corresponds to 0.38 g of phenylalanine and tyrosine per kg of metabolic weight i.e., a level of 3.83 g per 1000 kcal of metabolizable energy (ME). In a 4000 kcal ME/ kg diet, it represents a minimum level of 15.3 g/kg of dry matter. To maximize black hair color, an equal quantity or greater of tyrosine to that of phenylalanine is required (NRC, 2006).

Figure 1. Synthesis of melanin from phenylalanine.  

Figure 2. Influence of dietary tyrosine intake on color intensity in black cats. Diets that cause the color of hair to change from black to reddish-brown are associated with a reduction in melanin in hair, a decreased total melanin concentration and low concentrations of tyrosine in plasma. (©V. Biourge).

Environmental Factors

White cats are prone to squamous cell carcinoma, especially on the ear pinna and nose. Neoplastic changes are often preceded by solar dermatitis (sun burn). Solar radiation is the most ubiquitous mutagen but except indoor confinement, very little can be done to prevent exposure to sun light and the related free radicals. Research has shown the benefits of antioxidants in preventing UV light induced skin tumors and supplementation of antioxidants in the food may thus be useful (Liebler & Burr, 2000).

Age and Physiological States

In health and disease, age and physiological stage can greatly influence the quality of skin and coat. Growth, gestation, lactation, and old age will modify the nutritional requirements and are likely to interfere with the supply of nutrients to the cutaneous structures.

Obesity

The physical constraints related to excessive weight reduce the ability of the cat to groom. This can lead to skin and/or coat conditions such as matted hair or anal sac impaction. Any other painful factor limiting the range of movement such as arthritis or idiopathic cystitis will have similar consequences.

Concurrent Diseases

The skin is a large organ requiring numerous macro and micro nutrients. Any condition interfering with the absorption of those nutrients will have consequences on the skin and coat (Table 1).

Nutritional Balance

There is no published evidence of “generic food skin diseases” in the cat but, usually, when the diet is unbalanced, cutaneous signs often precede weight loss (Table 2).