Each year, Parelli trains over 400 horses per year, using highly trained instructors who treat the horses with the most respect possible. Parelli's training methods are some of the most advanced in the world.
No certain age. I know a 6 year old who can train them.
80,000,000.000
Two to three.
Too many.
50,000 horses die each year because of abuse and abandoning by the owners.
Many horses are saved from slaughter everyday, however just as many, if not more are not saved. There are many ways to help keep horses from being slaughtered, you can Google horse slaughter prevention and find many useful websites.
The number ranges but about 20 each year
3 a year
It is estimated that between 700 and 800 horses are injured or die from animal abuse each year. Many of these are race horses that are injured on the track. The number of animal abuse cases involving horses have went down since the closure of all US-based horse slaughterhouses.
29 thousand
163 this year
There were trains before steam power: animal and even people drawn. *Added - The first train is often debated, as is also the first railroad. People powered "trains" date to the late 1500's, and trains were still constructed for people power in the 1800's. Most early trains used horses and the first railroads in the US used both gravity and horses for the trains.