Like the lightweight sweatshirt in your gym bag, a cooler is a useful part of a working horse's winter wardrobe. Made from warm but breathable materials, coolers control the rate at which a hot horse cools down, reducing the risk of chills. Most coolers do this in three ways:
• by wicking moisture away from the horse's skin and onto the fabric's outer surface, where it evaporates.
• by blocking the wind, which will literally blow away the heat produced by the horse's body.
• by trapping and retaining warmth between the fibers of the fabric to act as insulation.
To get the greatest benefit from a cooler, toss it over your hot, sweaty horse and walk him until his pulse and respiration rates return to normal. Then, keep him in a draft-free area, with the cooler on, until his skin feels warm---not hot---to the touch. But be watchful while he is wearing a cooler: Some do not secure as well as regular blankets, which makes it easier for a horse to become tangled.
When your horse's coat is mostly dry and his skin feels nearly normal in temperature, you can put on his regular blanket and call it a day.