We grow rabbits for meat. The plan is that they end up in the freezer, but some of them die earlier, from illness, predators, misadventure, and even old age. Those, we bury. Other than treating them with respect, the idea is that they go back to the soil, because everything good goes back to the soil. We've long noticed that areas where we've buried a few rabbits have lots of worms. So, other than contributing their nutrients to the soil, they share those same nutrients with lots of grateful worms, who are attracted to the area, proliferate and, of course, give back to the soil.
Even if you don't have access to your own animals in need of burial, it might be worth bringing back roadkill animals to bury in your land. At least you'd be salvaging something from the tragedy, and it all looks the same from a worm's perspective.
I'd caution against using any parts of industrially-grown animals, because they'll be filled with pollutants you don't want in your soil. That's a tragedy you can't salvage anything from, not even food.