Baby chick with bare vent area

[2FishCreative]

Hi, have a baby chick, about 1 week old, and just noticed her vent area is bare. It is not red or irritated. I sprayed Ventricyn on it and that really bothered her and she began picking at the area, pulling some more down out. Any ideas of what this is and how to prevent/treat it? Thanks!

 

[oldhenlikesdogs]

Sometimes a chick has a bare bottom especially if they are growing fast. A picture may help.