WyldOne;
To throw in my uneducated opinion on the term "Corn Fed."
Back in the "Good Olde Days" most cattle were run out on pasture, called grass, or fed hay for most of their days. Being ruminants it didn't bother them.
However, if you wished to polish off a steer, means putting some fat on them which makes them look shinier and sleeker you would feed them a ration of corn while restricting their access to grass. Usually they were only fed corn for 30 days.
With horses, while they can live on grass they really like corn, you would feed corn for the same effect of making them look shinier and sleeker. Also increases strength and stamina of the animal.
So if someone wished to say that their women were sleek and shiny looking, with good health, strength, and stamina they would equate them to "Corn Fed". No frail, pale, fainting wimps need apply.