What a great insight. We recently lost a horse at age 28. The vet said he was in better condition than any other patient she had anywhere close to his age.
Alfalfa was a major component of his feed from his mid-teens on, depending on what he could eat. First it was hay, then soaked cubes (but he didnāt really like ārunnyā food, so it was drained a bit then served on top of his dry ration) then various brands of pellets (I had a hard time getting good quality) then Equidine, available at many Tractor Supply stores. For the last several years he was on equal parts Equidine, Purina Senior, and Purina Rolled Show Oats plus pasture 24/7. The Rolled Show Oats would get damp in his mouth and make it easier for him to chew. (He did have all but one of his molars and could graze until the end.
BTW, he was hit with one of neurological things, probably EPM. It turns out that old horses, even if in excellent shape, can have too little immunity.
If your horse can chew the alfalfa and does not waste too many leaves, I would recommend alfalfa hay along with the grass. But all of the leaves will lend up on the floor with a hay bag.
I am very happy with the consistent quality and easy-to-chew Equidine. It is intended to be the only food. I learned of it from our cutting horse trainer, who feeds the whole barn Equidine and does not have to haul hay to the shows or buy various local hay on the road.
Our younger horse, the one with little hair that is featured in another thread, came home entirely on Equidine and we cut her back as needed to balance her calories now that she has pasture 24/7.
If you use Equidine, do note that it contains enough mineral supplement to be a complete ration, so if you use mineral supplements just donāt overdo.
Some horses just canāt tolerate alfalfa, and you will know this pretty quickly if you try it.