Racehorses are very well looked after throughout their entire lives, there are very few exceptions and those found to be breaking welfare rules are harshly dealt with.
Reiterating some points already made, if they don't want to run they don't, if they don't want to jump they don't. Stables recognise this and respect it, the horses you see are the best, the ones who dont make it dont just simply get sacrificed, there are registration regulations for horses and if they were "disappearing" it would be flagged up, just like if you went missing. Yes they are trained to race but isn't that the case with all walks of life, would anyone here actually be better off without training?
A horse is put down from a broken leg due to massive complexities in attempting to heal, it can be impossible depending on the type of fracture, in alot of cases it would be more cruel to try to heal the horse. Sounds horrible I know but its the truth.
There has always been animal welfare groups trying to ban this race or racing, it has been analysed thoroughly for years and it still gets the go ahead from the authorities.
Those against it can lobby on various sites to add to the numbers but it'll be a waste of time, its actually becoming safer year on year out, verified by the safety of all 40 this year.
If you want to do something about horse cruelty go down the ladder to rich/large landowners who keep horses for a fad and then leave them to rot once the expense and novelty wears thin.
Anyway, lumped on Monbeg Dude. Dammit!