It can be tricky, feeding rabbits in a colony. My rabbits were on a hay-based diet (alfalfa/grass mix) with as many fresh gathered weeds and tree branches as the season provided and just small amounts of whole grain. In winter the diet was adjusted somewhat, more root crops and less leafy greens because here in Ontario we get a fair bit of snow. The rabbits did well and problems with too much internal fat were minimal until, as my arthritis began to limit mobility, I had to rely on my son to feed them. He had a heavy hand with the grain and when I decided our rabbit-raising days were over, the does had a lot of internal fat when butchered. The buck, however, was quite lean and in great shape.
There is no way to tell which rabbit gets what in a colony, so you have to feed enough that no one gets stinted. Free-choice hay helps and it also helps to have more than one feeding station for concentrates.
Colonies are difficult and require an alert eye and the ability to think on your feet in order to troubleshoot effectively. Until a rabbit person has several years raising rabbits in cages, I really don't recommend it.
