Your GSD took down a full grown (healthy) cow? Are you sure that you don't have a wolf problem that has caused your dog to become more aggressive and territorial?
I can understand your GSD feeding off downed cow carcass, but I have a hard time understanding a lone GSD taking down, killing, consuming a full grown cow.
Hondo Von Dopplet L Bauernhof "Hondo"- GSD
Lilie's Tug McGraw "Tug" - Golden Retriever
Maggie - Mini Dachshund (Rescue)
Lonestar Pivo - Texas Blue Lacy
Ashe - Barn Cat
Katie / APHA