Hair growth cycles are established during foetal life. After birth hair growth cycles vary depending on genetic and growth factors, age, breed, sex, location (region of the body), hormonal influence, stresses, nutrition, blood loss, high fever, acute onset of diseases, numerous environmental factors (day length or photoperiod, grooming, harsh climate, friction and trauma), clipping , grooming and drug therapy.
Dog’s compound hair follicle and cyclic hair growth: Each cycle consists of an active growing phase, anagen; followed by a transitional phase, catagen, in which the hair bulb becomes pinched off from its dermal attachment; and a resting phase, telogen, in which the hair is retained in the follicle as a club hair and is eventually shed. There are approximately 100-600 hair per sq cm of dog skin. This mosaic pattern of the coat ensures that not all hair is shed at once. Anagen may be considerably shortened under conditions of ill health so that a greater percentage of hair are in telogen and are thus more easily shed.
Telogen defluxion is recognised in many species including the dog, in which there is an abrupt, premature cessation of anagen which causes a sudden synchronous flux of many hair follicles into telogen. This condition may be precipitated by a variety of stressful circumstances, such as high fever, shock, severe illness, pregnancy and lactation, anaesthesia and certain drugs. Hair are shed profusely about 2-3 months after the stressful event and a new wave of hair follicle activity commences.
Hair coat type of breeds: Breeds like Golden Retrievers’ thick double coat is made up of a plush undercoat and a furry layer on top. It’s that warm and fuzzy undercoat that causes the most mess. While a Golden Retriever sheds lightly throughout the year, as with every double-coated dog, he sheds his undercoat in large quantities twice a year. The ratio of primary to secondary hair density is important in determining coat type in dogs. It has been reported that the proportion of dogs moulting in this continuous fashion varies according to classification of coat type; hence wire-haired breeds are less prone than short-haired, long-haired or coarse-haired breeds. Poodles and Bedlington Terriers do not shed their coats in a cyclical fashion, although hair loss will occur at continuous albeit slow rate.
Photoperiod (light exposure): Living conditions may affect the predisposition of dogs to begin moulting. Moulting is likely to begin sooner in dogs living indoors, particularly in long-haired breeds. This effect is seen in indoor dogs who are exposed to many hours of artificial light and moult continuously throughout the year.
Hormones: Hormonal disorders are a common cause of alopecia (hair loss) in dogs. Hormones influence metabolism and growth have a non-specific action on hair growth and thus the rate of shedding. Therefore, any condition resulting in imbalance of thyroid hormones, corticosteroids, sex hormones and growth hormones etc influence hair growth and shedding.
Skin diseases: The most common causes for hair fall are fleas, mange, allergies, bacterial or fungal infections, to name a few.
Nutrition: Hair is composed of 90 percent protein and as a consequence up to 30 percent of the body’s daily protein requirement is utilised in the processes of hair growth and epidermal keratinisation. A nutrient deficiency may also result from feeding poorly prepared or over supplemented diets, poor storage conditions or an individual susceptibility to the condition as a result of disease or genetic factors. Deficiencies of protein, essential fatty acids, zinc and vitamins A and E appear to be the most important causes of nutritional dermatoses. Therefore, nutritional skin problems are rare when a well balanced, complete diet like Pedigree Small Breed is fed, but may occur when the animal’s intake is reduced due to stress or disease.
Waltham studies have clearly demonstrated that addition of patented zinc and linoleic acid, an omega fatty acid in the balanced and complete diet associated with significant and substantial improvements in skin and coat condition. These include shiny coat, reduced dandruff, soft coat and improved coat feel.