Nowadays its harder to eat an old horse once its useful life has finished as there are certain drugs that can't be used in the food chain and the horse can't be put to sleep with drugs but had to be killed mechanically. Companion and athlete horses need to be passported and removed from the food chain.
Cows sheep and pigs are easier to raise for food, two of them are dual purpose and the pig can be raised in a small space and fed on household scraps and vegetable rubbish.