There has been an on going discussion about feeding corn. Most pellets are made with corn, but not all. There is some information that suggests that whole corn may cause gut impaction in rabbits. I am not convinced of this, but cage rabbits do get much less exercise than their colony-raised or wild cousins, so I guess it is possible. Some suggest cracked (cut) corn. Cracked corn has a tendency to mold with a white or pink mold in moist conditions which is harmful to rabbits. I would be more afraid of the mold than the whole corn.
I have been conducting some trials lately using a mixture of oats, wheat, and cracked corn, and alfalfa hay. I have seen no adverse affects. Perhaps, the argument may best be studied in degrees-of-risk. Show rabbits tend to be both more valuable and more inbreed. House rabbits are valuable to their owners in a different way. I raise meat rabbits. I have already proved to myself that cross bred meat rabbits are more healthy and have more vitality. I have produced upwards of 375 meat kits in the last 2 years, and have lost only one to anything besides 3 or 4 day old kit getting out of the nestbox when it is cold. My kits aren't as valuable to me as a high quality show rabbit or house rabbit is to their owner, so I am will to take more chances. It could be that the corn I feed has just not caused a problem and bitten me in the butt....YET, or it could be that my crossbreeds are just healthier.