Here's the break down.
Cow or spike takes 4 goats. Big bull takes 6 goats or multiple trips. Huge bull takes..... well if I ever get a huge one I'll let you know.
I generally bone out the meat and split it into goat loads as soon as I get one down. (25lb bags)
I bring out the head when I go out to get the goats because thats the most unwieldy load and you can carry it without a pack frame. Having already bagged it, I have a good idea how many goats its going to take. I'll carry a load as well if it keeps me from making another trip. I've been known to load the goats extra heavy if its not over a couple miles to the truck and not too steep and nasty.