I know this post is humorous, but I think you are on to something. Why not just follow the Masai tradition? You poke the cow in the neck and drain blood into a gourd. Then you milk it and mix the two together and drink it. The cow heals up and you can "poke a hole in it again" another day.
Assuming, of course, that the cow know you well enough to let you do it, and doesn't kick or stomp the snot out of you. (Cows can kill you a lot easier than you can kill them, they outweigh you by 7 -10 times if full grown, and they don't even need horns to do it, although that would also make it easier).
I think a lot of responder have never seen a cow outside of disney . . . : )
I saw a steer take a hydraulic bolt to the head, shake its head, and stand there. It took three tries and a 22 shot to finish it off. Their skulls are pretty think. My friend thought he could put one down with a 45, but he shot it in the forehead where it is thickest, and it took a couple of shots. The funny part was he did it in the middle of town (kind of like Napoleon D.)