Of all the horses an owner might winter, the Mustang asks the least and hides the most. Descended from horses that survived winters on open range with nothing but windbreaks and their own coats, he grows a notably thick winter coat, conserves energy shrewdly and regards cold, dry weather with indifference. The risks in his winter are not the obvious ones. They are the things that thick coat and that independent streak conceal: slow weight loss, a water supply he has stopped visiting, and a herd hierarchy quietly starving him of hay.
Trust the coat, verify the horse
A Mustang's winter coat is long and dense, and unmelted snow lying on his back is a good sign — his insulation is keeping body heat in. Blanketing such a horse usually flattens the coat's loft, introduces rubbing on a horse unaccustomed to rugs, and can cause real distress in a recently adopted Mustang who has never worn one. Leave the rug off unless he is old, ill, clipped for some reason, or losing condition despite good feeding. The corollary is that you cannot judge him by looking. Once a week at least, get hands on him, or watch him handled: press through the coat along the ribs and over the hips. On an easy keeper you are watching for gain; on a Mustang in his first domestic winters, just as often you are catching loss that the coat disguises until it is advanced.
Windbreak, not walls
What a Mustang needs from shelter is a break from wind and driving wet, not necessarily a stable. A three-sided shed, a dense tree belt or a landform dip all serve, and many Mustangs prefer standing out with their backs to the weather. Check the shelter's social reality, though: if one horse claims the shed, the Mustang at the bottom of the order may spend the winter in the wind anyway. Spread hay in more piles than there are horses, spaced widely, so everyone eats without a confrontation — forage is warmth, and a horse driven off the hay is a cold horse by morning however thick his coat.
Water in a freeze, for a horse who may not come to you
Mustangs that range to drink once or twice a day can be hit hard by a frozen trough they visit at dusk to find solid. Break ice at least morning and evening, and keep a check on how much the level is falling; a shy drinker will not stand at the trough while you hover, so judge by the water, not by watching him drink. Reduced intake on dry winter forage is the classic prelude to impaction, and a Mustang showing few droppings, restlessness or a tucked-up belly in cold weather needs a vet the same day, with a plan for catching him calmly if he is still wary of people.
Feet and the long view
Those famously hard hooves still need picking out when snow packs and balls in them, and a check for cracks as winter ground alternates between frozen ruts and mud. Beyond that, winter asks patience: consistent, undemanding contact — the weekly hands-on check, feed delivered the same way at the same times — builds the trust that makes every other season's care easier with this horse. The Mustang wintered well is mostly left alone, but deliberately, by someone who verified rather than assumed.
That verify-don't-assume plan is easy to lose when several people help, so KinsLe Family Sharing keeps his winter notes — no blanket, hay piles spread wide, ribs checked by hand each week — in the shared profile everyone involved can read before they head to the field.