Copper One of the many functions of copper is to assist in production of connective tissue and the pigment melanin. A deficiency in dietary copper is also related to collagen abnormalities, hypopigmentation of the skin, and alopecia. Sources for cats include liver and supplements in the forms of copper sulphate and cupric oxide. Selenium Selenium works with vitamin E as antioxidants to remove the free radicals that are damaging to the body and the skin. Selenium also plays a role with other antioxidants to help maintain cell membranes which provides further protection from free radicals causing oxidative stress. Oxidative stress plays a role in development of skin diseases. Dietary sources of selenium are naturally occurring in selenomethionine and tuna. Essential fatty acids A fatty acid molecule consists of a (COOH) group attached to an aliphatic chain. There are many types of fatty acid with different such chains. These different types have somewhat different properties. Saturated fatty acids have no carbon=carbon double bonds, while polyunsaturated fatty acids have more than one such bond in each molecule. The main form of fatty acids in diet is fats or triglycerides, which consist of three fatty acid groups attached to a glycerin molecule. Fatty acids can become attached to different molecules such as carbohydrates or proteins, and can implement a wide range of functions in the body. These functions include long-term energy storage, insulation (prevents heat loss, protects vital organs, helps transmit nerve impulses faster), structure, transportation around the body for nutrients and other biological molecules. They can also be precursors to other compounds in the body, such as hormones (some of which are important for gut/immune/overall health). The length, degree of saturation and configuration of a fatty acid affects how it is broken down, absorbed and used in the gastrointestinal tract. Essential fatty acids (EFA) are nutrients that cats are unable to produce in sufficient amounts to meet their needs, or at all. All EFAs are polyunsaturated. EFAs also vary in size, have many different functions and can also be further divided into other categories, two of which are very important for gastrointestinal health: the omega-6 and omega-3 fatty acids. (The omega number denotes the position of the first double bond in a fatty acid, counting from the methyl end.) These fatty acids are most effective when present in adequate and appropriate balanced ratios dependent upon stage of life and production of the