You may notice as early as late August that horses start shedding their short summer coats. They do this in response to the amount of daylight. As the daylight hours shorten, the horse begins to grow a longer coat. This is triggered by the light that enters the horse's and glands that govern hair growth is activated. The short hairs of the summer coat fall out, and longer hair grows in its place to help the horse stay warm throughout the colder weather.
The best way to prevent this growth of long hair is to keep your horse under controlled lighting. This is done with show horses to control their hair coat growth and broodmares to regulate their breeding cycles.
Feeding For Optimum Health
The next-best way to prevent your horse from getting a thick coat is to make sure he is well fed. A very hungry horse will be a cold horse, and the body's response will be to grow a thicker coat to compensate. Feed your horse lots of good-quality hay in the winter, and supplement with concentrates and mineral. That will keep his internal furnace stoked, and it will be easier for him to stay warm. Digesting all that fiber will generate a lot of heat, and that in turn, will keep him warmer in winter. Many horses, as long as they are well fed and have shelter from wind and wet, don't need anything more than good food to keep warm.
For a healthy well-fed horse, a blanket may help prevent long hair growth somewhat.
A sturdy turnout blanket can help protect your horse from chilly drafts and damp weather. It may not be as helpful for preventing a long coat as cold is not the only factor governing the hair growth cycle. A lot has to do with the amount of sunlight he's exposed to.
The Best Types of Blankets
Generally, a stable blanket is not considered as safe for wearing in the pasture as a turn-out blanket or rug.
Stable blankets often lack the leg straps and extra belly straps that prevent the blanket from shifting as your horse moves around outside. They are not waterproof, and that could leave your horse wearing a soggy blanket if it rains. This is counterproductive as it means the hair will be flattened and lose the natural loft that would keep your horse warm. Use your stable blankets indoors and a turn-out rug outdoors. During a sunny winter, you may notice your outdoors horse start shedding by the end of January. By the early months of spring, the shedding will be much faster.
If your horse has already started to grow longer hair for winter, you can stall the process or reverse it by keeping him indoors under controlled lighting. A study from the Texas A&M University suggests that sixteen hours of artificial and natural light are needed to keep hair short throughout the year. This can mean a lot of stall time for your horse. That's not always the best for your horse's mind or body. You'll have to balance the pros and cons of long stable time and installing light timers and fixtures against your plans and goals for your horse.