You've got ranchers in places like Wyoming where the forage is barely sufficient to keep livestock alive. Cattle raised under these conditions have to be fattened up before they can be sent to a slaughterhouse. Typically these cows will be shipped to another ranch that specializes in this before then being shipped to market. It sounds like the guy quoted in the article is running one of these secondary "fattening" ranches.
Since grain (or in this case candy) has a much higher energy content than grass, cattle can be raised to market weight much faster than if they were fed a grass diet.
"Ranch" isn't really what we're talking about here; cattle are sent from ranches to feed lots for fattening (which is what this guy is running, hence the ability to gin up new chemi-food on site.)
Feed lots are very highly concentrated populations of cattle that are fed a regulated diet of grain (corn) mixed with concentrated antibiotics and, in this case, rotten chocolate. Another commenter already referenced Pollan's work, which exposes the tradeoffs of this industrialized approach. Among these are increased e.coli outbreaks (as e.coli concentrate in the rumen of the cow when it tries to digest grain,) and the increased likelihood of antibiotic-resistent bacteria developing because of the tremendous amount of antibiotics used to keep animals living in these conditions from getting sick:
Since grain (or in this case candy) has a much higher energy content than grass, cattle can be raised to market weight much faster than if they were fed a grass diet.
Edit: I accidentally a word.