If you use one of these, I'm curious what you put inside? I have a hen w/ fatty liver disease so I prefer not to put in seeds or fatty treats. I like rolled oats and dried meal worms. But the girls kick them all out in about 15 minutes. I'm trying to make it harder for them to get the treats out and make the fun last longer. I tried chopped up parsley and raisins this morning and that lasted about a half hour. Any other ideas would be greatly appreciated.