Was factory beef farming (in the USA) the result of government-subsidized corn? In The Omnivore's Dilemma, Michael Pollan writes that industrial beef farming, in the form of concentrated animal feeding operations (CAFOs), is dependent on low corn prices for its cost-effectiveness. He also implies that corn prices low enough to justify CAFOs were only possible because the US agriculture policy artificially depressed the price of corn.

Pollan attests that the first CAFOs began in the 1950s. But he also spends a good deal of time in the previous chapter discussing how Earl Butz, under President Nixon (that is, in the 1970s), was instrumental in ending the New Deal corn price stabilization policies (a buffer-stock scheme) and replacing them with corn supply subsidies (direct payments to farmers).

If that's the case, then how did the first CAFOs manage to be profitable, or even seem like a good idea, if corn was not to become artificially cheap for at least another decade? Or were CAFOs always profitable, but received a tremendous boon when corn prices were later driven down by policy?

This is as much a question about the timeline as it is about the underlying economics, so I'd prefer to see an answer based in some kind of scholarly source.

Also I'd appreciate it if someone with more than 150 rep could create an "agriculture" tag for this question. I had wanted to add "prices" and "subsidies" tags as well.
Was factory beef farming (in the USA) the result of
  government-subsidized corn?


Answer A) The answer is negative, according to 

MacDonald, J. M., &amp; McBride, W. D. (2009). The transformation of US livestock agriculture scale, efficiency, and risks. Economic Information Bulletin, (43). USDA.

Although not a historical-statistical account, they write (p. 21, bold my emphasis)


  "Two recent reports argue that Federal commodity programs reduce prices for a particular input, purchased feeds, and that those
  reductions drive structural change (Pew Commission on Industrial Farm
  Animal Production, 2008; Union of Concerned Scientists, 2008).
  Specifically, they assert, drawing on Starmer and Wise (2007), that
  policy encourages increased production of feedgrains, that the
  increased production substantially reduces feedgrain prices, and that
  the buyers of purchased feed benefit from lower feed prices. While
  producers of homegrown feed have been the direct recipients of
  commodity payments, the reports argue that the payments have not been
  large enough to offset lower commodity prices, so that commodity
  programs have largely benefited large-scale animal feeding operations
  at the expense of smaller diversified crop and livestock farms.
  However, the size-related differences in production costs that are
  summarized in figures 6-8 cannot be attributed to the effects of
  commodity programs. In developing cost-of-production estimates, ERS
  prices homegrown feed at its market value—that is, the price that
  homegrown feed would have drawn as feed in regional feed markets—and
  does not attempt to estimate the actual cost of producing the feed. To
  the extent that larger operations realize lower feed costs in ERS
  estimates, it is because they use less feed per cwt of production and
  not because purchased feed costs them less.
  But even if commodity policies reduce purchased feed prices, there’s no reason why that should alter the size structure of livestock farms.
  No technological barrier prevents small farms from replacing homegrown
  feed with purchased feed: if purchased feed prices are lower than the
  costs of growing feed, then small livestock operations can simply buy
  feed and realize the same savings as large farms. A difference
  between the price of purchased feed and the cost of homegrown feed
  does not explain why feeders build large rather than small
  operations."


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Answer B) The answer is positive according to

Starmer, E., &amp; Wise, T. A. (2007). Living high on the hog: factory farms, federal policy, and the structural transformation of swine production. Tufts University.

They report the following estimations, among others: The feed costs for Hog represent ~$60\%$ of operating costs of CAFO's. That in the period $1997-2005$ feed subsidies meant that feed was sold at a price $26\%$ below production cost. Hence, the savings in operating costs for CAFO's was around $60 \% \times 26\% \approx 15\%$ (of Costs, not of Revenues). For  the top four CAFOs in terms of market share, the authors estimated that this amounted to total cost-savings of $\approx 4.4$ billion USD for the 1997-2005 period.  

This paper appears to be an aggregator of previous more detailed studies, so lots of references.