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.
To get the most value from hay, it is advisable to put it in a hay feeder of some type. Hay feeders reduce the amount of hay that horses waste. In many situations, hay feeders will cut waste by 20% or more. For many operations, a hay feeder will pay for itself in just a year or two.