interesting. yes, i saw the corriente breed, but i think dun's article on the spanish castas actually tells more. when i look at the corriente it has similarity, but its not quite 'toro bravo'.
re docility and the difficulty of keeping these bulls, i travelled in spain and we visited a couple of ranches. my spanish isnt so good, so i wasn't able to get all my questions answered, but we did go out in the pastures where these bulls are (in land rovers that had various puncture holes in the doors). and if you stay a certain distance from these bulls, they are fine. the entire art of toreo (spanish for bullfighting) is about manipulating what's called "jurisdiction", or the invisible space around a bull that he'll protect. the space is elastic -- when he first comes into a ring it's huge, and he'll charge at anything. but gradually, through work with the capes, his jurisdiction shrinks until the moment when a matador can kill him by hand. for the record, the most points go for a quick clean kill, a sword stroke through the aorta. anything too gruesome or grisly is abhorred by the judges and crowd, and if the kill isn't clean they send a guy in with a little dagger to sever the spinal cord just behind the horns, so the bull dies fast.
anyway, re pasturing and keeping -- what i gathered in the translations is that males are kept together, so they do socialize. i saw them butt each other a lot though, to test or assert their dominance and probably exercise their muscle. they are kept within their age group -- 4 year olds together in one pasture, 3 year olds together in a different pasture, etc. they don't bring them into a barn ever -- they basically live out there wild -- but consider that it's spain, mexico, etc, where winters aren't bad. but food, vitamins and medicines are taken out to the troughs. the mayoral (head of the ranch) goes out in the land rover regularly to look over and observe the bulls (like to notice if any look sick). if any *are* sick enough to need real care, i imagine they'd need to shoot it or otherwise kill it. a fighting bull is not allowed to be close to a man on foot ever, from the day he's born and branded, to the day he goes to the arena.
what i don't know is how they get the bulls into the trucks that transport them to the arenas -- but somehow they do it. it's a good question. but apparently these bulls are sold to the arenas for $5000 or more each, so i guess you'd have to calculate the value of feeding them but basically leaving them alone, then dealing with the headache of getting them into a truck once.
i love that photo by the way -- it really does show how magnificent these animals are. i do realize it's good for profit and production to have bred their natural aggressiveness out, but it's kinda sad too, when nature made them so powerful.