I don’t have any exact figures, but that matches with my experience.
Part of the reason may be that sweet corn has been bred to taste good; field corn is bred to produce high yields.
Also, sweet corn is picked when it is actually immature. Field corn is not picked until Fall, and has many more weeks to grow bigger ears.
That is some serious hard pore corn.
The problem is that feed corn is generally measured by bushels of shelled corn (no cobs). the standard weight of a bushel of dried corn (15.5% moisute) = 56 lbs. Yields of 150-200 bushels per acre are not unusual in a good year. (There are a lot of fields that yield much more than 200 bushels.)
I found a cite that said the corn cob adds about 16 pounds per bushel, but it didn’t say at what moisture level. If the moisture levels are equivalent, let’s say that a 150 bushel yield weighs 10,800 pounds
Sweet corn is measured by weight, cobs, leaves, kernels and all. Also, sweet corn is harvested at a much higher moisture level. The corn is measured by crates, which have a defined weight of 100 pounds. A full-season vareity can yield about ~130 crates per acre.
So, very roughly speaking, people corn yields about 13,000 pounds of high-moisture ears, leaves and kernels per acre, while cow corn yields about 10,800-14,400 pounds of low-moisture ears and kernels per acre.
Uh, for the record, I didn’t mean to imply that it was literally animal feed that we were eating, as it was quite obviously being used as people feed. The teasing involved calling it animal feed. For the rest of us Americans, we plainly consume lots and lots and lots of non-sweet corn, too. Sweet corn tortillas and corn chips would be pretty gross, and corn flour wouldn’t work the same if there were a high sugar content. I’m not sure that it’s even possible to make popcorn with sweet corn (anyone?).
So, maybe 2X or even 3X? By wieght?
I love hominy (whole kernel as opposed to grits). Interesting process to make (lye/alkali soak) and it really does change the taste and texture a great deal. What type of corn is used to make hominy?
A question for you Brits: My mum is British (WWII War Bride). She said they never ate corn in England, it being reserved for livestock. Has this situation changed? Do you now grow/import and eat corn?
I’m sure there are several varieties available but the one I’ve grown is called “Hickory King.” Makes great hominy and corn nuts. It would be considered a field corn type.
Our pigs did not eat the cobs.
The Other Master speaks.
Well, no. The vast majority of feed corn is harvested by a machine called a combine. This machine separates the kernels from the cobs and husks in the field. The corn kernels are fed into a hopper for transport to a storage facility. Cobs and husks are dropped back onto the ground, adding organic material to the soil.
That’s not to say that cattle and hogs won’t eat ear corn, because they will. It’s just that hauling and storage of ear corn is very inefficient. The cobs and husks have little nutrient value in them, and are better left in the field.
The stuff is really quite delicious. Since it is always in season when it’s my birthday my wife usually prepares a dish with huitlacoche. This year it was a chicken breast stuffed with roasted corn and poblano chile and panela oriada (similar to an aged mozzarela) and covered in a salsa of huitlacoche. And since the subject is corn, we had handmade tortillas of nixtamal or fresh corn dough and not made from commercial corn flour.
The following morning, because she had made extra stuffing we had omelets with it and more huitlacoche sauce.
And also, we always eat fresh and never canned. Like most things fresh is always far better.
Yeah, corn-on-the-cob or sweetcorn is now common in supermarkets - even to the extent of having fresh (rather than shrinkwrapped) corn in season, along with all the corn products such as chips etc. Another one of those american imports 
I’ll put it on my list of things to try right after surstromming…
I’m British
In the early 1960’s we would go to France, where maize was grown, but dried on the cob and fed to sheep.
My parents would approach farmers in the fields and ask to buy it, they regarded us as mad, and would give it to us.
The British certainly ate sweet corn in the 1960’s - and I’ve never seen it used as animal feed in the UK - well not on the cob.
Your loss. It’s an edible fungus just like chanterelles, truffles, tree ear fungus or the common button mushroom.
No, I’m serious. Last time I was in Sweden I failed to score a tin of Surstromming because the supermarket I went into at the beginning of the week had lots, and I thought I’d get some just before I returned. Needless to say, at the end of the week all was gone. I like trying odd foods, providing they’re not actively dangerous.
Corn is all the same in the end.