The ranchers who continue to breed horses to keep the rodeos and race tracks supplied with freash new horses to abuse are to blame for all the excess horses.
Animals, like humans, should be cared for and loved untill it is their time to pass on.
Not until some arrogant human decides they are of no more use (because it can no longer bring in dollars for them) and sends them off to be killed.
If you own an animal it is your moral resposibility to care for that animal until it is their natural time to pass over.
We don't with sending our senior citizens off to some slaughter house, because we are running short of care homes to look after them.
In some parts of Africa they do eat human meat.