The most visible aspect of a pet’s health is the condition of his coat and skin which represents most visible signs of wellbeing and vitality.
The skin is a large, metabolically active organ system that serves to protect the body from injury and infection, aid in temperature control and immunoregulation, and act as a storage reservoir for certain nutrients. The coat also plays an extremely important communication role in the bond between pets and their pet parents. Good nutrition is essential to normal skin health. Dietary factors may play a role in the etiology and therapy of skin disease in three arenas, i.e., nutrient deficiency or imbalance, nutritional supplementation for therapeutic effect and dietary sensitivity. The most common nutrients deficiencies of which affect skin and coat include proteins, essential fatty acids, certain vitamins and minerals.
Causes of nutritional deficiency…
Many factors like heredity, gastrointestinal parasites, ectoparasites, health status, grooming, hormonal disturbances, physical or chemical trauma, sequel to metabolic or functional disorders and nutrition play important role in determination of skin condition in dogs. Feeding of pet dogs in many western countries is managed chiefly through proprietary food which is complete and balanced to meet AAFCO nutrient profiles suggested for dogs. As a result, the occurrence of nutrient deficiencies is rare. However, in India most of the pet parents depend upon homemade food to feed their dogs who are usually restricted to a few components. Thus, nutrient imbalances can occur due to feeding of poorly formulated or improperly stored commercial food, imbalanced homemade diet or as a sequel to metabolic or functional disorders that affect the ability to digest, absorb, or use nutrients. Food allergy or hypersensitivity may also be one of the causes.
Symptoms of nutritional deficiency…
The prevalent nutritional deficiency symptom includes inflammation of skin also known as dermatitis, itching, alopecia, lusterless hair and coat, scaly skin, etc. Although many nutrient deficiencies may be associated with skin disorders, most produce a similar range of clinical signs. In most cases, the skin develops seborrhea, which is characterised by abnormalities in sebum production and/or keratinisation. Typical signs of a nutritional dermatitis include excessive scale, erythema, alopecia or poor hair growth and greasy skin, which may be accompanied by secondary bacterial infection and pruritus. It is generally accepted that signs become evident only after feeding deficient diets for several months.
Nutrients for dog’s skin…
Protein: Both hair growth and skin keratinisation create a high demand for protein. About 25-30 percent of a pet’s daily protein requirement is needed for maintenance of skin health. Hair is composed of ~95 percent protein, which is rich in the sulfur-containing amino acids, methionine and cystine. Primary protein deficiencies are most likely to occur when requirements are increased as in young, growing animals and in pregnant or lactating females. Poorly formulated diet leads to protein deficiency which is evident by cutaneous lesions with hyper pigmentation of epidermis, colourless hair, impaired hair growth, delayed wound healing, excessive scaling, hyperkeratosis, flaky skin, and increased hair breakage. Sub-optimal protein intake can decrease hair or wool production and decrease fiber diameter, length and breaking strength. Dietary correction involves supplementation with high quality protein sources, such as meat, eggs and milk.
Essential fatty acids: The palatability of canine food depends on its fat content. Also fat provides energy and essential fatty acids. Linoleic acid is an omega-6 (n-6) fatty acid that has been shown to be a dietary EFA for dogs. An EFA deficiency affects many systems of the body. Because of the high rate of cell turnover in the skin, the integument and hair coat often show the first obvious signs of deficiency. A dry, dull coat is produced, hair easily breaks off and sheds, and skin lesions develop. Over time, the skin becomes pruritic, greasy, and susceptible to infection. Generalised flaky desquamation, coarse, lusterless haircoats or alopecia, and pruritus are among the changes seen with essential fatty acid deficiency. Dogs are unable to synthesise linoleic acid; thus, a dietary source is essential.
Vitamins: Vitamins are the essential dietary components required in very small amount for various physiological and metabolic processes in the body. The vitamin requirements are usually met through properly balanced diet or by provision of micronutrient supplements. However, inadequate and imbalanced diet may lead to predisposition for various deficiency diseases. Deficiency of vitamin A and B-complex predisposes manifestation of a variety of cutaneous lesions.
Vitamin A (retinol and its derivatives) has many physiologic functions and is involved in the regulation of cellular growth and differentiation, essential to maintain the integrity of epithelial tissues. Vitamin A is detrimental; if in excess or deficient shows lesions of hyperkeratinisation and scaling, alopecia, poor hair coat and increased susceptibility to microbial infections hence also known as anti-infectious factor. Cocker Spaniels, Standard Poodles, Akitas, Chow-Chows and Vizslas are more susceptible for vitamin A related skin diseases. The B-complex vitamins are necessary cofactors in numerous metabolic pathways, and so deficiencies affect many body systems, including the skin and hair coat. Deficiencies may occur, nevertheless, after prolonged oral antibiosis, anorexia or when water loss is increased as in polyuric conditions or enteritis. Occasionally, deficiencies of individual B-group vitamins arise as a result of interaction with other dietary
In general, skin lesions associated with deficiencies of B-group vitamins include dry, flaky seborrhea and alopecia. Nonspecific signs of deficiency include weight loss, anorexia, alopecia, and the development of a dry, flaky seborrhea. Biotin deficiency produces a characteristic alopecia around the face and eyes with crusting in severe cases. This condition may occur in the unusual circumstance of feeding large amounts of raw egg whites which contain avidin, a protein that binds biotin and prevents its gastrointestinal absorption. Riboflavin deficiency can cause a dry flaky dermatitis with reddening of the skin and hair loss, also produces cheilosis in addition to seborrhea but will not occur if the diet contains meat or dairy products. Pantothenic acid deficiency can lead to loss of hair pigment and hair. Niacin deficiency is possible only when the diet is low in animal protein and high in corn or other cereals that are a poor source of tryptophan. Vitamin A deficiency results in pellagra (humans) or ‘black tongue’ (dogs) with ulceration of mucous membranes, diarrhoea and emaciation and, occasionally, in a pruritic dermatitis of the hind legs and ventral abdomen. Pyridoxine deficiency may cause a dull, waxy, unkempt coat with fine scales and patchy alopecia but has been reproduced only in experimental studies.
Minerals:The most common minerals responsible for skin and coat health include copper, zinc, manganese, iodine and selenium. Zinc plays a critical role in regulating many aspects of cellular metabolism, a number of which are concerned with the maintenance of a healthy coat and skin. Zinc is a component of a number of metalloenzymes that are necessary for normal lipid, protein, and nucleic acid metabolism. A supply of dietary zinc is needed for the maintenance of epidermal integrity, biosynthesis of fatty acids, metabolism of vitamin A, and maintenance of immunological function. Because rapidly reproducing tissues have a high demand for this mineral, signs of deficiency are seen in the skin and hair coat. Skin lesions are usually seen on the face, over pressure points, and on the footpads. Affected areas are characterised by hair loss, redness, inflammation, crusting, and pruritus. In the adult, signs of zinc deficiency are confined mainly to the skin, but these may be accompanied by growth and other abnormalities in young animals. Cutaneous signs are characterised by focal areas of erythema, alopecia, crust and scale, which develop symmetrically around the extremities, mucocutaneous junctions and pressure points of the limbs.
Absorption of zinc can be inhibited by excessive levels of dietary calcium, iron and copper, which compete with zinc for intestinal absorption sites. Dietary phytate, which is found in cereal-based diets, chelates zinc, and high levels may also hinder intestinal zinc absorption. Most cases of zinc-responsive dermatosis in dogs were associated with the feeding of poor quality, cereal-or soy-based dry food, whose effects may have been exacerbated in some animals with a simultaneous inherent defect of zinc absorption. While naturally-occurring deficiencies of copper, iodine, manganese, and selenium are not common, it is important to recognise the importance of these essential nutrients when formulating diets designed to promote skin health and optimal hair coat for companion animals. Copper is needed in the skin for the conversion of the amino acid tyrosine to melanin. As a result, one of the signs of deficiency of this mineral is depigmentation of the hair coat. Although frank deficiencies are rare, interactions with other minerals in the diet can affect copper status. Iodine is required by the body for the synthesis of the hormones thyroxine (T4) and triiodothyronine (T3) by the thyroid gland. Diets that are deficient in iodine cause a number of symptoms, including the development of skin lesions and a poor hair coat. Manganese is another mineral needed as a cofactor in several enzyme systems that catalyze cellular metabolic reactions which regulate nutrient metabolism. Because a deficiency affects cellular growth and lipid metabolism, signs will be observed in the metabolically active integument. Selenium is an essential component of the enzyme glutathione peroxidase, and like vitamin E, functions to protect cell membranes from oxidative damage. For this reason, selenium is important for the production of normal skin lipids which in turn protects skin.
Feed a balanced diet
Skin and coat condition can be used as an indicator of canine health. Many physical, chemical and biological factors can influence the health and well being of the skin. Cost, availability and religion taboo abide most of the pet parents to feed nutritional unbalanced homemade foods or leftovers to their dogs which leads to nutrient imbalances and predisposes the animal to nutrition related dermatosis and other related skin diseases. Hence properly balanced food should be fed to our beloved companions for their nutritional health.
(Dr KB Kore is technical sales manager at AB Vista South Asia, (Pune), a UK-based multinational firm for animal feed supplements; Dr SS Patil is assistant professor at Junagad Veterinary College (Gujarat); Dr PP Mirajkar is livestock development officer in the Government of Maharashtra; and Dr AV Patil is key account manager at Adisseo (Mumbai).