Then they're sent to a feed lot for some period of time to fatten up.
Ah, from the article you linked: "However, comparisons of FCR among different species may be of little significance unless the feeds involved are of similar quality and suitability."
So cattle might be more efficient than appears at first glance, since as ruminants they're initially fed stuff you can't feed other animals (ADDED: including humans), especially "on marginal land where agriculture isn't ideal", or perhaps as part of a crop rotation cycle. Alfalfa is a 3-for, a rotation cycle that's not e.g. corn or soybeans, a nitrogen fixer, and tasty food for cows.
And all the above isn't the best for our topic at hand, for that alfalfa and such isn't stuff we can digest, nor is silage from corn leftovers, so it mostly feedlot cow food we could redirect to humans.
"More than half the U.S. grain and nearly 40 percent of world grain is being fed to livestock rather than being consumed directly by humans"
http://news.cornell.edu/stories/1997/08/us-could-feed-800-mi...
The title of your link: "U.S. could feed 800 million people with grain that livestock eat, Cornell ecologist advises animal scientists"
What, and give them type 2 diabetes?!?!!
Seriously, a lot of the usual suspects should reconsider their animus towards animal husbandry in the light of the increasing evidence the move to a low fat, high carbohydrate diet caused and is causing untold morbidity and mortality.