There are
-4 outside the Regulator HQ.
-3 in Canterbury Commons.
-3 in Arefu.
-2 in The Republic of Dave.
-2 in the Charnel House raider camp.
-1 in Paradise Falls
-1 in Megaton
OFC this doesn't count all the ones being used by the 4 big merchants, the base game's randomly encountered generic wasteland merchants, the ones added in Broken Steel's water caravans, or the 2 or 3 herds of wild brahmin that exist in the C.W., since those aren't being raised as a food source.
New Vegas has Brahmin being raised in pens for food in
-3 in Novac
-1 outside Raul's shack.
All the others are being used as caravan animals by the Crimson Caravan Company, and not for food.
-The communities in the C.W. aren't large. They have a combined population about the total of The Boneyard in the Fo1/2era.
-http://fallout.wikia.com/wiki/Hilltop_Farm_ruins
These people tried it, then got killed by raiders, and their "farms" only amounted to radioactive plants and mucky water. That's kind of a big point of Fo3, its impossible to farm because the water is radioactive, and the ground is equally so.
-Unfortunately NV has a massive plot hole in that all the farms, except the ones in Goodsprings, and I think Nellis has one, all come from the NCR, or use NCR made/repaired things like the Vegas water system. Same with the brahmin, 99% of them are from the NCR's Crismson Caravan Company. Which leads to the question....... what did they eat for the 200+ years before the NCR came into the Mojave region and gave the all these farms and Brahmin since the Mojave lacks the resources needed to handle such a population itself?
-Mutfruit can be found in the merchant lists of every food seller in the C.W., including
--Jenny Stahl of the Brass Lantern in Megaton.
--Gary Staley of Gary's Galley in Rivet City.
--Margaret Primrose of Cafe Beau Monde in Tenpenny Tower.
--Doc Hoff's merchant caravan.
It's one of the singular most commonly sold food items in the game.
-OFC he doesn't plant them in D.C., that would be pointless as they wouldn't grow, just like everything else that isn't grass or mutfruit in the C.W. And punga is so popular it can be found in The Pitt, so long as both DLC are installed at the same time. What do you thing the smugglers are smuggling? Punga is the only thing anyone owns in Point Lookout.