Ok... Just my topic
Ok first of you need to chek under the doc of his tail and his stomach for lumbs or sists tht maybe white... This could mean ur horse may have cancer... If thats the case u may have to make the hard decision of putting him down... But i also suggest you feedbur horse beat pulp... Mix it in woth hos sweet feed... Read the instructions to soak the pulp overnight its soft and easy to eat and digest... I hoPe this helps u and answeres ur question
If he spits out hay or grass, this could mean that his teeth need floating. The teeth need to remain flat to be able to grind, and if they are long with points, grinding cannot take place, food will be spit out or dropped, and so the horse will not ingest food. Please have your vet "float" his teeth or find a qualified equine dentist to do so.