There is a feed crop for animals that has been grown since the Middle Ages, but not widely known (or grown) in the U.S. today. It's the lowly mangel, and I've put in an experimental garden bed of them this year.
Mangels are a root crop. Root crops generally do well in our area so I thought I'd try to grow some for use this winter as a supplemental feed for our chickens.
Supposedly they can grow up to twenty pounds and two feet long. (Oh, my.) This one I pulled from the garden a couple of days ago is about the size of a medium-large potato. I doubt any of mine will reach the twenty pound mark, but if we are fortunate enough to get a long fall this year, I'm sure they will bulk up a bit more than this.
Although a copious quantity of information on the mangel does not seem to be readily available, I have read that they have long been considered excellent feed for a variety of livestock including cattle, pigs, sheep, rabbits, goats and chickens.
The mangel seeds look much like chard or beet or turnip seeds as do the greens and roots. Like turnip or beet greens, the leaves are edible by humans as is the root when harvested young. One source suggested mangels can be boiled and mashed like potatoes.
Nutritionally they are lower in sugar content than beets and contain more protein. They're touted as a valuable energy source.
They even have a history in jolly old England of being used to brew a potent alcoholic beverage.
So if you're looking for a good energy source or nice ale to serve your livestock with their daily ration of grain, mangels might be worth looking into.