On average, the untreated HIV infected patient will progress to AIDS in about 5-10 years. Since 1996, the introduction of powerful anti-retroviral therapies has dramatically changed the natural progression of HIV infection to the development of AIDS.
You CAN feed your horse just hay, but you have to up the portions and it also depends upon the type of hay you are feeding. Alfalfa mix is normally the best but there again, you're goinng to have to feed more hay to make up for the not feeding grain when you are riding.
Hay that is overly mature when it is cut has little nutritional value to the horse due to an increase of a component called lignin, which is completely indigestible for the horse or the microbes in the gut flora. Horses can easily digest nonstructural carbohydrates, mostly in the small intestine.