When to blanket your horse or not is a dependent on several factors. The most common reasons for blanketing your horse are the age and condition of the horse, how often you work your horse during cold months, and personal choice. In general, horses do not need to be blanketed when they are in good condition with ample access to proper food and water. Horses are designed by nature to grow the coat they need for the coming winter. Just because you might be cold does not mean your horse is cold.
The conditioning of your horse carries a greater weight in deciding to blanket your horse than their age does. Healthy is healthy no matter what age you are. It is a good idea to blanket your horse if your horse falls into the following categories:
Underweight horses or ones that have a hard time keeping weight on will benefit from blanketing because it allows them to preserve energy from being lost just keeping warm. They may start out the winter in good condition and start dropping weight as the winter progresses. Increasing how much food they are getting and ensuring that what they are eating has enough nutrition to support their needs is essential for them to maintain conditioning through the winter. Even when you do blanket you must check the condition of the horse under the blanket. If they are not getting enough to meet their needs they can still lose weight even if they are blanketed. Horses can be underweight at any age.
Working horses that get consistent exercise through the cold season benefit from being blanketed. Blanketing early in the season prevent their coat from coming in as thick as it would if they were not blanketed early. This allows them to cool off quicker after strenuous workouts. When you blanket early in the season then you have made a commitment to blanket your horse for the duration of the cold months. Care needs to be taken to adjust warmth of the blankets used to the outside temperature.
Horses healing from an injury or illness may require blanketing when they are not able to regulate their own body temperature. It takes energy to heal. Blanketing during times of stress helps to minimize stress and allows their body to focus energy on getting healthy instead of keeping warm.
The best indicator of when your horse needs the extra warmth that a blanket can give them is if they are cold. Horses shiver just like we do when they are cold. When your horse is happy and content without a blanket, even on the coldest of days, you can be happy and content that they are warm.