Should my horse wear a blanket in the trailer?

The LSU AgCenter's equine specialist, Dr. Neely Walker, writes in a cold-weather hauling publication that blanketing "may or may not be required" and should be judged on exactly those four things. Her two examples: a body-clipped horse hauled alone in an open-sided stock trailer will likely need a weighted blanket, but a horse with a full winter coat in an open-sided stock trailer should not need one.

Company matters too. LSU says that as the number of horses in a trailer goes up, so does the body heat, which reduces the need for blanketing. A hauler quoted in The Horse's winter-travel article put it this way for a full load: a sheet would be fine. And Horse Council BC's transport guide, written by Jennifer Woods, says a horse with a heavy winter coat that lives outside usually doesn't need a blanket, while a light-coated horse that spends the winter indoors will need one.

The table gathers what each source says. It is a map of the advice we read, not a rule: none of these sources gives a fill weight for travel, so we don't either. For picking a weight in general, our blanket weight calculator and Barn Talk on blanket weight are the places to start.

LSU says heat inside a trailer can build up quickly even in extremely cold weather, raising the humidity and possibly making the horse sweat. Horse Council BC puts a number on it: the temperature inside a trailer is usually 5 to 8 degrees C (roughly 9 to 14 degrees F) higher than outside, and it says heat stress is more of a threat to a horse than cold stress.

The University of Kentucky's extension horse program (Ashley Griffin, 2020) says a heavy blanket in a poorly ventilated trailer can cause horses to sweat and become overheated, even in cold weather, so don't over-blanket. The Horse's winter-travel article says the same from the veterinary side. Dr. Catherine Kohn of The Ohio State University is quoted: the horse is too hot if he's sweating under the blanket, so check under blankets frequently. The article's author adds that overheating is more common than chilling in hauled horses, and that trapped heat raises humidity, which increases sweating and fluid loss.

Sweat then brings its own problem. A hauler in the same article says a horse that sweats is damp, and a draft is more dangerous for a damp horse. So the aim the sources keep returning to is a horse who is neither chilled nor sweating. How to read that on the horse is in Is my horse too hot or too cold under his blanket?.

Horse Council BC calls ventilation the most critical part of the trailer environment and says horses still need fresh air circulating in winter, without a gale-force draft blowing straight on them. It adds that ventilation weakens as more horses are added and when the trailer is parked.

LSU's advice for cold weather: the instinct is to close the vents and windows, but ventilation is key. Opening the roof vents in reverse, toward the rear, will draw heated air out of the trailer, and opening the windows slightly is recommended if more fresh air is needed. Fresh air also moves mold spores, urine and manure fumes and dust out. In The Horse, one trailer builder says to use windows rather than storm doors to let air out in winter, and the article's author suggests screened windows to keep out snow and moisture and notes that a trailer should not be drafty.

Insulation changes how a trailer behaves, so the same blanket can be right in one rig and too much in another. If you're unsure how your own trailer breathes, a thermometer is one thing Horse Council BC recommends for watching conditions inside. Ventilation is also why the table above says "depends": two horses, same coat, different trailers, different answers.

One of the people quoted in The Horse's winter-travel article says that even in winter, horses sweat because they are nervous. Horse Council BC notes that a horse that is stressed is more susceptible to heat stress. For a nervous traveler, then, the blanket decision has two parts: how much heat the trailer holds, and how much he generates himself.

One rider describes the same pattern below: a horse who gets nervous on winter hauls, and a cooler used in place of a heavier blanket. That is one rider's experience, not a recommendation for your horse; it is here because it shows how the sources' advice looks in a real barn aisle.

Horse Council BC is direct: don't transport a wet horse in cold conditions, because a wet coat makes the horse very susceptible to cold stress, and a horse who sweats in a warm trailer is wet again. Its advice is to cool and dry the horse before loading.

EQUUS (January 2024) describes the usual way to get there after a winter ride: walk for 10 to 15 minutes so heat in the muscles can dissipate, cover him with a cooler, which can be wool or a high-tech fabric that pulls moisture off the horse, and check him often. It says to blanket only after his temperature has returned to normal and his coat is dry, and warns that putting a hot, sweaty horse away can let him catch a chill. If he is still sweating an hour after cooling down, EQUUS says it may signal tying-up or another serious condition and you should call a veterinarian.

What is a cooler, and how is it different from a scrim or a fleece? We cover the lineup in What is a scrim sheet? and the wet-coat basics in Can I blanket a wet horse?. You can browse the horse coolers we carry; the point here is only that a moisture-wicking layer is a different job from a warm one.

Horse Council BC says not to blanket a horse on warm-weather trips; if you must use one, it should be light and let heat escape. LSU's summer hauling sheet, also by Dr. Walker, lists dehydration, heatstroke and exhaustion among the problems to prevent, and recommends avoiding the warmest time of day, opening trailer vents for airflow, parking in shade with air movement, and, if you're stuck in traffic, keeping as much ventilation as possible without unloading the horses.

LSU also suggests two rubber mats on the trailer floor, which it says reduces the heat on the horse's legs, and says not to let a horse ride with his head out of the window because flying debris and bugs can cause serious eye injuries. A fly sheet or summer sheet is a different product from a blanket; if a sheet is on your mind, see What is a scrim sheet? and the fly sheets and summer sheets category.

The Horse's article says to check for overheating at each watering stop rather than just confirming the horse is still standing; one hauler there says to look at the neck and shoulders for sweat. Dr. Kohn's advice is the same: check under blankets frequently.

On water, the sources give slightly different intervals. LSU's cold-weather publication says to plan to stop every three to four hours to water the horse, and that room-temperature water makes a horse more likely to drink. LSU's summer sheet says to stop and check vitals and offer water every four to five hours, with each stop lasting at least 20 minutes. Both note that some horses won't drink while hauling. Your vet knows your horse and your route; the numbers are a starting point.

If you've adjusted the blanket mid-trip, change one thing at a time so you can tell what helped. Shipping boots or wraps are a separate topic: Horse boots explained covers what they are for.

The extension sources are general, and none of them knows your horse. EQUUS says a horse still sweating an hour after cooling down could have tying-up or another serious condition, and to call a veterinarian. Dr. Kohn's rule of thumb in The Horse is that sweating under the blanket means he's too hot; your vet can help you work out why a particular horse keeps doing it.

For the wider question of whether he needs a blanket at all, see Does my horse even need a blanket?; and if you're wondering whether a winter coat will stay in if you blanket early, see Will blanketing stop my horse's winter coat?. For sizing and weights, our horse blanket guide is the long version.