It is funny that millions of people are totally fine with eating cows and chickens, and get all emotional at the thought of eating a horse. Horses are pretty animals, and cows are not.
https://spca-sofla.org/horse-slaughter-in-oklahoma-legal-under-new-law/
In Oklahoma there was a ban on horse slaughter for many years due to the horse lobby. People with old or injured horses that were really expensive to keep had no option but ship them to another state to be slaughtered. It is not practical to dig a BIG ol' hole and bury them as they can contaminate ground water.