First, I would get a current weight on the mare so that you can track weight gain or loss during stall rest. You will then want to monitor her weight on a weekly basis. Using a weight tape is fine for this as long as the same person takes the measurement in an identical manner each time.

Second, as you alluded to, she will require fewer calories. For stall rest, I recommend cutting out all textured or pelleted concentrates and switching to a ration balancer product. This is a low-calorie feed that will provide the amino acids necessary for repair of damaged tissues and the minerals and vitamins required for maintaining the health of the mare. Follow the feeding directions for the weight of the horse. The activity level would be considered maintenance.

Third, provide hay at 1.5-2% of the mare’s body weight. It may take a couple of weeks to figure out the amount of hay necessary to not cause weight gain. It should be mostly grass hay, but giving a little alfalfa may help to prevent the development of ulcers. A mixed hay with grass as the majority plant type is ideal. If you do not have the mixed hay, add a flake of alfalfa per day to the other forage.

To keep the horse from eating hay too quickly and being bored the remainder of the day, you might want to consider one of the special hay bags that allows the horse to get only a little bit at a time.

Careful vigilance will help your normally active horse get through this period of convalescence.