I've seen the Anthony Bourdain No Reservation episode covering parts of Uruguay - he said they outnumber people three to one. I've read some stuff online (believable or not) that states five of them to every Uruguayan citizen.
Whatever the actual stat is doesn't matter too much. My own eyes have seen a lot of cows in a small country housing very few individuals. Uruguayans absolutely treasure their asados or their chivitos chock-full-oh-carne...hence they need a lot of these vacas.