My thing is, that death separates the flesh from the soul. The animal is dead. How is it less respectful to make use of the flesh, than to let it rot and be eaten by worms, or to incinerate it -- do they even do that for a critter as big as a horse? So if you don't bury them, what do you do with your horse when it dies?
I could not eat my dog that I bonded with. And I do not know that I could feed rabbits or chickens to myself or my dogs if I raised them and named them. If I was raised on a farm, eating hogs and beef cattle would be a way of life, and I probably wouldn't feel queasy about it. But for now, I will leave the idea of raising rabbits and chickens for dog food. I know I couldn't raise horses to be slaughtered for dog meat.
But, if a friend had a horse that broke its leg, and they had to put down, and we knew someone who could process the meat into chunks or burger, yes, I could feed it to my dogs with no problem whatsoever. With no more problem than feeding them deer, beef, or chicken.
I don't know if I would want to eat dog, or bear. I think herbivors make better meat sources than carnivores. They were eating horses when the people were starving after WWII. They eat horse in France. I could probably eat horse meat. It couldn't possibly taste as bad as deer meat. I wouldn't try turtle or gator or snake or dog or cat or bear. I would try sheep though. How much you wanna bet that the definition of lamb in dog food probably stretches to include old ewes and rams that are ready to put into the stew-pot. But it is also probably an excellent source of dog food if you could raise them yourself, and aren't squeemish about butchering them and feeding them to the dogs.
Ah kibble, it's nasty, but you really do not have to think about it as all the little critters who go into it.
As for being an animal advocate, well, then you should approve of horse and cow eating, and disprove of rabbit and chicken eating. Figure 800 pounds of meat, and one critter sacrificed, as opposed to a 4 pound rabbit or 8 pound chicken. I have to cringe at the thousands of chicken lives my dogs each year. If I was feeding beef or horse, it would probably be just a few.
And rather than send those horses to mexico to be shipped to France to be slaughtered for feed, why not use that meat here in America to feed dogs? The horses are just as dead, whoever is eating them.