Do you like horse racing?
I love horse racing, when it is done ethically. I used to work at a feed store where we made deliveries to some of the biggest equestrian facilities in FL 
Do horses work well in humid hot air?
They can, but they have to be monitored. Humidity and heat breed mold like no other, if they eat moldy feed they can die same day if they aren't cared for and there is much suffering involved
Wow, that doesn't sound very good for their health at all.
Yeah, the quality of hay is up-mostly important too, if it isn't dried right or it gets wet and they eat it they can colic. 
Can't they eat carrots aswell? what are their foods?
Carrots are totally game, they LOVE apples and oats. They are important for their nutrition especially for ponies and rich in risveritol