The quality of the skin barrier function depends on the lipid synthesis in the protective layer. A lack of enzymes, vitamins or minerals will affect the synthesis and therefore the strength of the skin, according to Christoph Mülling, Ph.D., D.V.M., professor of veterinary anatomy, University of Leipzig, Germany.

 

Skin is the largest organ of the body and the first layer of defense in any animal's immune system. Poultry are a unique challenge. Though somewhat protected by feathers, a bird's skin is very thin and loose, which makes it vulnerable and easy to damage. Bird-feet skin also remains vulnerable and often develops pododermatitis, which causes discomfort and can reduce a bird's desire to move and feed.

 

Besides being a protection against harm, the bird's skin also acts as the business card of the industry. Consumers do not like to see a product with a damaged or unequal-coloured skin. Trace minerals such as zinc hold a key role in maintaining skin integrity.

 

Dr. Mülling says a bird's feathers provide some protection to the skin. After that, the skin's defense depends on its layered structure and differentiated cells.

 

The outer protective layer of the skin is made of numerous living and dead (cornified) cells of variable thickness. These cells are organised on top of the dermis and can be differentiated as basal cells, spiny cells and the horn (cornified) cells. Basal cells are active cells anchored to the dermis. While they grow, they develop into spiny cells and ultimately into horn cells (see cell differentiation). To prevent disintegration, the cells are connected by means of tight junctions, desmosomes and intercellular substances. The desmosomes are the receptors for dermal signals that occur between cells.

 

The spiny cell layer is similarly structured. Here lipids establish an intercellular permeability barrier. On top of that layer, there is a protective keratin layer containing horn cells rich in lipids. This keratin layer is also the final stage of cellular conversion from living, epidermal cells into dead, flat horn cells.

 

In poultry, the horn layer, or stratum corneum, has a barrier function with a "straw and mortar" organisation, notes Dr. Mülling. The horn layer in poultry is far less stable and protective than the skin of mammalians, which have a more "brick and mortar" structured horn layer. Nevertheless, it usually meets the primary function of being a barrier to water loss and invasion from undesired microorganisms.

 

Since a bird's skin is very thin, a network of blood vessels can be found at the border between the subcutis and dermis, and within the dermis. Thus, even a small injury will create an open access to the blood stream and a freeway for infection.

 

Trials initiated by Dr. Alba Fireman, Research and Nutritional Services (RNS) regional manager - South America, Zinpro Corporation, confirmed Dr. Mülling's statement that micronutrients play a role in developing a strong and healthy skin in birds. Dr. Fireman's research focused on the functional properties of trace minerals like zinc, manganese, copper and selenium. Each of these minerals play an important role in developing the skin and maintaining its integrity.

 

Research findings show that there is much to gain when feeding the right dose of bioavailable trace minerals. These studies show that feeding Availa®Zn improved birds' skin integrity and also improved immune resistance. Similar improvements in skin puncture strength were obtained through adding Availa^®Z/M to the feed. Zinc also proved to be effective in reducing the incidence and severity of pododermatitis in broilers. These trials prove that providing sufficient levels of easy-to-absorb trace minerals play an important role in developing a strong and healthy skin to support immune function.