Do you mind if I ask why in pots? I assume that because you have so many rabbits it is an agricultural venture and potting would seem a very bad choice for the economics of it.

I agree, keeping the trees in pots will greatly stunt their growth after only a couple of years. You'll get so much better yields by having the trees in some fertile ground. If it was me, I'd plant them really densely, maybe 6 foot spacing.

All you need to figure out is how much leafage they need-for how long and still remain reasonably vigorous. That probably would entail allowing them to remain unpruned for a month or two before going into dormancy.

No long term advantage to planting them real close if they were in the ground- they'd fill the space so quickly.

Planting would be nice and I'd frankly rather, but I'm on just a third of an acre. Most of my place is already planted, so I'll need to move these around a bit to manipulate light/shade and replace them easily at need. *sigh* How I WISH I had five acres...LOL...

The idea is to let them grow out new branches that are about 2' long, harvest those, and repeat. I suspect that harvesting half the material at a time, letting the cut half sprout, then harvesting the other half, will be sufficient to keep the roots and tree happy. They will essentially be short bushy stubby things, not actually trees. :)

If you have the room, why not plant hybrid willows? the rabbits like the branches, and they will provide more greenery, and they take well to yearly severe pruning.

The nutritional profile is markedly different--mulberries are very close to the profile of alfalfa. I had planned to stick a couple of willows in there for fun and medicinal use, though. :) Mulberry, moringa, willow, and the garden should be sufficient to keep things varied and still keep the nutrition within reasonable bounds, I hope...!

And the rabbits are your protein?

What is the reason that you would not want to plant fruit bearing MB? Enjoy the fruit in Spring and still produce leaves for your Summer wabbit food. Do wabbits eat MB that fall on the ground like chickens do? Also, MB are so eager to take over the world that you should expect them to promptly grow roots through the pot drain holes and anchor the pot down right there.

Rabbits will eat mulberries. I have meat rabbits and one of my breeder does loves grapes!

Couple of reasons--fruitless produce more leaves which are also more palatable (I currently have both fruiting and fruitless and have been testing. The rabbits just don't like the Morus nigra leaves--they're smaller and tend to collect more dirt/sap/bird poo). So while they enjoy mulberries (as do I,the dogs and the chickens, along with every robin in twenty miles), that's only six weeks in the year, and the fruit is definitely more a treat than a feed. The fruitless just go nuts doing the leaf thing, and I know that they are used for coppiced feed in other countries where silkworms are raised for just that reason. (And who knows, maybe silkworms are my next livestock! LOL!)

Know what you mean about the 'grow through the pot and into the ground'; my poor potted roses usually do that before I get them planted! LOL! I'm hoping that having the pots elevated on 2x4s will help me at least catch the darn roots for a trim before they get to the ground. :)

Rabbits also need the twigs to work their teeth. I grew up on rabbit, and my grandfather used to give them bread, apple peels, lettuce or cabbage cores and other greens refuse, hay - and fresh apple, pear or willow twigs (the chickens and the dog would get the household refuse that did not fall in those categories). I agree that mulberries provide more nutrition, it is not a bad idea. But you should also consider other high nutrition, high production leaves, for example just about any Eleagnus (maybe not seaberry, those thorns are awful).

Because my main diet for them is still going to be a solid balanced pellet, I'm not too terribly worried about doing the whole thing with greens--besides, I need the higher production that goes with the pelleted ration. The leaves are just supplemental to help defray the cost a bit and to give them a treat once a week or so. They surely do enjoy those branches--I have to go through the next day or two and remove all the peeled bits. :)

With eggs, fresh vegetation in the chicken's diet seems to improve the quality of the product, I wonder if the same doesn't hold true with the meat. Have you noticed any difference in flavor when your rabbits are fed a more varied diet?

I raise chickens (11), ducks (23) and rabbits (6 does 2 bucks). With chickens yes truly free range birds eggs are very different from store bought. Here is a picture I took for comparison. Both are chicken eggs.

Look how orange and rich the egg from my bird is compared the the yellow yolk on the store bough egg.

On the rabbits I give mine a lot of bidens alba and mulberry but have noticed no difference in the taste of the meat.

The rabbits I can buy here at the farmer market, I asked the guy and he told me they eat pellets, are vastly inferior to those my mother prepares when I visit. I am no longer even buying them. Meat animals need fresh food too, and in particular all of them need fresh greens. If I find someone who raises them in tractor trailers on pasture, like chickens, I will buy them again.