Shedding of a horse’s winter coat is a complex physiological process that can reveal information about the horse’s general health.
Many — well actually all — horses look cosmetically “messy” during the shedding period with a thorough shed usually occurring over a six- to eight-week period. This transition period often accompanies the fickle weather of spring and offers the horse a buffer of comfort until the weather settles into its seasonal warmth. The end of a complete shed usually coincides with the appearance of green grass and a heavy warm spring rain.
The major driver and trigger for shedding in a horse is the increasing hours of daylight that occur around the spring solstice. Ambient temperature, stabling practices and blanketing will also have an influence upon the shedding, just to a much lesser degree. Grooming and exercise, even 30 minutes a day, expedite the length of the shedding period, most likely because both processes increase the blood flow to the skin and stimulate hair follicles.
Shedding patterns ie. the rate of shedding and order of body parts shed does exist amongst horses with individual horses tending to remain consistent to themselves from year to year. Although the “patchy” shedder can be particularly unsightly, it is rarely a reason for concern unless the horse is pruritic. If the horse is noticeably itchy and the shedding is occurring in patches it would be advisable to examine the horse for external parasites such as chewing and/or biting lice or ticks.
The increase and decrease in daylight hours trigger the production of hormones responsible for hair growth and shedding. In order for the skin and hair coat to stay healthy and for effective shedding to take place, the horse must receive proper nutrition. The quality of the “shed” is highly dependent upon nutrition and hormonal communication within the body. Proper mineral and fatty acid balance are necessary to formulate the hormones which the body relies on to internally signal shedding of the hair coat.
If the horse is not shedding normally it may be a clue that something is awry with the horse’s health. In younger stock, incomplete shedding can be an indication of underlying poor nutrition or parasitism. Typically these horses will stubbornly retain the long “cat” or guard hairs under the belly, chin and throat-latch. Horses that carry a heavy intestinal parasite burden begin to look unthrifty, lose body condition and shed out poorly as the worms draw nutrients away from the horse. Once dewormed a parasitized horse will quickly shed its remaining winter coat.
One of the most prevalent reasons for failure to shed or inappropriate shedding, particularly in older horses, is equine Cushing’s disease, also known as pituitary pars intermedia dysfunction (PPID). This is a hormonal imbalance common in older horses. Rarely does the change in shedding pattern happen in one season with this condition, rather it occurs over a number of seasons with shedding of the hair coat becoming increasingly troublesome for the horse. Owners who have a historical account of their horse’s shedding are usually best able to detect these early subtle signs. Changes in the hair coat occur steadily over several years.
Most obvious are delayed shedding, increased length of the hair coat and retention of long hairs especially under the jaw, in the jugular groove, underside of the neck, and alongside the backs of the limbs. Hair coats can become excessively long, shaggy and curly. Ponies can show quite a marked hypertrichosis and/or abnormally long and curly hair growth whereas horses will tend to exhibit the more subtle signs of abnormal shedding.
This may simply be longer guard hairs along the legs or a noticeable delay in shedding over the years. These signs are often an early indicator of Cushing’s disease and would warrant further blood work and attention by a veterinarian. Identifying these horses early is critical to their management as many of these horses are particularly sensitive to the development of laminitis and/or founder.