Whether you're looking to feed your calves something specific or the bigger cattle are keeping all of the feed to themselves, a creep feeder may be a good solution to consider.
A creep feeder’s basic function is to let the calves in and keep the adults out. This is done by making very specifically sized entrances which will allow the calves in and keep the adults, who are much larger, out.
According to Rob Hand, there are both advantages and disadvantages to doing this. A few advantages are that if you recently finished weaning a calf, it will help reduce the shrinkage that it experiences. Also, in a time where the calf may be vulnerable after weaning, the creep feeding may reduce the risk of the calf getting sick, by ensuring its ability to eat.
There are also disadvantages to creep feeding. Unless the creep feeder is frequently moved, the area around the feeder will likely get overgrazed. There is also the chance that a cow may lose productivity if it was too fat as a calf.
For a great resource on creep feeding such as the effects, rations, facility measurements and additional advantages and disadvantages, take a look at the Alberta Agriculture and Rural Development website.