A healthy horse will have a shiny coat with the degree of shine depending on the time of year and grooming practices. During colder months, the coat will appear more fluffy and less shiny than during warmer months.
With some practice, you'll be able to determine how healthy your horse is and notice if changes are taking place that need to be addressed.
Older horses, especially those with ailments such as Cushings Disease, will maintain longer, less shiny coats even during the warm months. Younger, well-nourished, active horses usually have naturally shiny coats. Draft-type horses will have coarser, less glossy coats at any age.
Affects of parasite infestation on the coat
Horses that are heavily infected with a number of internal or external parasites will have a rough, scraggly, dull coat. In some cases, fly or gnat bites will result in scabs or blisters on the skin and open the way to disease and attacks by other parasites, causing the coat to appear uncared for.
Fungal infections of the coat
Although patchy shedding occurs in most horses in the springtime as weather warms, shedding that results in matting or clumping of parts of the hair coat often indicate a fungus infection.
Importance of proper nutrition to horse coat health
Horses that don't receive enough feed or that eat feed that is not nutritionally balanced will have a dull coat. Any diet that is low in the amino acid lysine, lacks minerals and vitamins, or has a low protein-to-energy ratio will cause the coat to lose it's luster.
Sun and sweat exposure
Exposure to sun will cause the color of the horse's coat to fade. Salt from sweat will dull the hair coat and may irritate the skin of the horse if not groomed properly over a period of time. Some horse owners elect to keep normally hairy winter coats clipped to allow the horse to dry quickly after being ridden or exercised. Keeping the hair clipped makes the horse less susceptible to becoming chilled and possibly ill, and makes grooming easier and more effective.
Horse glandular problems
The condition of the horse's coat sometimes indicates glandular problems. Excessive growth of the coat, along with coarser hair, may indicate problems with the pituitary gland, a common condition with aging mares. Some glandular problems are associated with wasting diseases which cause a loss of the layer of fat beneath the skin. These conditions often cause the skin to become dry, resulting in a dull, brittle hair coat.
In general, a healthy horse will have a smooth, fine, glossy coat, while the coat of a horse in ill health will lack the luster and shine derived from skin oils, making it dry and coarse.
Any time your horse's coat changes drastically or becomes rough, coarse, or spotty in appearance, check the horse carefully or consult with your veterinarian. By doing so, you will be able to catch any developing problems and take preventative steps to ensure the health of your horse.