Something you use to feed creepy horses?
Nope. Some breeders like to introduce their foals to solid food before they're weaned. A creep feeder is a manger with bars across it. The bars allow a foal's head to fit, but not that of a grown horse. It's used to give special food to the foal.
Without the bars, the mare would eat the lot (horses are greedy animals, trust me).