A thought.
How many people raise their horses with butchering someday in mind? Not many, I'd guess.
So... say a 10 or 15 or heck, 30 year old horse..... thats 10 years worth of Ivermectin and other wormers administered to that horse once a month, or at least multiple times a year... 10 years of chemical insecticides in the way of fly sprays, livestock powder, ect... often administered daily or weekly.
10 years of antibiotics, vaccinations, steroids, and who knows how many other prescription medications that have kept the horse in health in an unnatural enviroment to this point.
Despite the fact I woud never eat a horse, period, I'd certainly never eat an animal raised without regard for safety of consumption! Those who do will likely wish they hadn't, sooner or later.
Back to the OP....
I've been to Pocatello.. about 6 years ago. A family friend from long before I was born lives there... (he was one of the Marlbro men, hehehe) and I visited him with my father. Pocatello is such a dry, dry, dry place! Almost a desert. It might be this fellow can't feed his horses anymore? If that's the case and he absolutely had to do the kind thing for them... he should at least do the right thing by the horses and the people and call animal control to rescue them, or put them down humanely and bury them properly. They'd probably be just as healthy for eating in that state as they were before the fact.