Well depending on what part of Texas Bermuda hay might be easiest.
horse=livestock+hay
You can feed Jiggs Hay to a horse. Jiggs Hay is a hybrid and designed to be easy to grow, and more nutritious for the horse.
There is no one best hay for a specific breed of horse. Each horse, no matter what breed they are is an individual and needs a custom feed plan. That being said most grass hays are roughly equal in nutritional value, so as long as the hay is fresh, good quality and clean it should not matter what type it is.
The best horse to start with would be an older horse (like 10-15 or older )experienced in what you want to do.It also depends on the trainer,rider/owner, and environment around it.
No, horse feces does not turn into hay. Horse feces is composted and it turns into horse manure. This is used as a fertilizer.
Any hay can founder a horse, it is not what the horse eats but how much it eats. Some feed can founder a horse faster than others. Peanut hay is one of those.
Hay!
Hay-Burner
Are you asking is it okay to ride a horse when they are on just hay? It is completely fine to ride a horse that is on just hay. My horse is fat as a cow and she was on all hay, no feed all summer. I rode her regularly.
Yes, you can feed a horse wet hay as long as the hay is completely free of mold and/or maggots. Feeding a horse moldy hay can cause colic, and be fatal. Make sure all hay left out is covered with a tarp, and even check that hay. Runninghorse
No second cut hay often has more nutrients in it than first cut hay. But if the horse is overweight or not working much then first cut hay would be better if the horse will eat it.