I understand and appreciate that you care for your mare and want to do the best for her! I fully agree that she is very likely to have ulcers, and from personal experience, can attest to how serious ulcers can be. I agree about not using ANY 'sweet feed'(grain mixes w/ molasses, basically); they are generally now agreed to not be the best choice for horses. I have several years' experience in feeding a STEAM extruded, FORAGE-BASED, concentrate,"Total Equine", which is very safe, very digestible, and has an excellent overall nutritional profile. The 'pellets' are more like a light, crunchy but not 'hard', nugget, which breaks now very quickly in the presence of liquid, including saliva. It is safer than most GRAIN-BASED concentrates, as far as referring of thin,even emaciated, horses. The primary ingredient IS alfalfa; it can be fed along with pasture, alfalfa hay, or good grass hay. Some horses may take a bit to accept the difference in texture, but I've yet to have one reject it over time. I am currently keeping an almost 32 YO mini mare, whose teeth just aren't very effective anymore(even w/ regular tooth care for the 29+ years I've owned her), in good condition on a diet of about equal amounts of RABBIT PELLETS and Total Equine, along w/ daily ground flax, @ 3 c. of soaked beet pulp, and a handful of alfalfa leaves; she cannot effectively graze, and risks choke on any sort of hay(and refuses any soaked pellets.)Alfalfa is indeed a good choice now; it is probably the most nutritionally complete forage(Hay)plant available for horses; of course, should be weed, mold, and dust-free and of good quality. Absolutely agree about sticking with the ulcer treatment for as long as it takes...30 days AT LEAST, IMO.Read up on how much is a TREATMENT dosage, and on when to dose in relation to when she is fed/eats; the timing 'can' make a big difference.I read just recently of a 'new' product for 'hind gut' ulcer treatment(they can have stomach ulcers, AND ulcers in the hind gut; takes different strategies AND different 'stuff' to treat, so I've read); name of it is 'Equishure'? or similar: am sure you can google it.I also have become a strong advocate of slow feeding; it is a HUGE benefit to ANY horse not able to be on 'full-time' suitable pasture, IMO.
I ended up having to euthanize a gelding I raised, trained, and dearly loved to drive, as he was my very BEST mover and had the heart of a lion...due to ulcers, which despite years of battling them, finally made him so he wouldn't even try to graze,much less eat any other form of feed. It was one of the saddest things I've ever had to do: I learned a lot from the experience, though, and hope that any input might help spare others from the awful experience.
Best wishes
Margo in NM