I have an aged pony that can’t eat hay and can minimally eat grass. His weight is kept up by getting 2 meals a day. They are LARGE meals that he dines on over a 8-10 hour period. I soak his feed, 1lb of beet pulp, 3lbs of timothy pellets, 3 lbs of alfalfa cubes, two times a day. He munches on this mash throughout the day and night. He will eat for 10-15 minutes then go lounge for a bit, eat a bit, lounge a bit. His mash is kept in a space that only he can enter (he’s 14.1, the others are over 16 hands).
How many lbs of hay is your horse getting a day?
What type of hay is your horse getting?
What brand/type of feed is your horse getting?
How many lbs of this feed is your horse getting?
If your horse has teeth and he is in a space to eat his hay by himself, I would up the quality and quantity of hay first (and net it to reduce waste).
If the increased (quality and quantity) of hay doesn’t cause an increase in weight, or a maintenance of weight, and your horse has time in a separate space, I would consider adding some straight alfalfa hay in addition to his regular ration or a bucket of soaked alfalfa cubes or pellets.
You might also consider adding a sheet or blanket when the temperatures get low. The added insulation can help to conserve calories.