I find that poultry don't have the ability to lick the treacle up so I just use them for my sheep, which I believe is what they are designed for.
Treadle feeders, on the other hand seem to work ok, but takes the hens a while to get used to them. I use a bit of wood to keep the lid partially open so they get to know where the food is. Then after a while I leave the lid closed and they then step on the treadle while looking for the food, and lo and behold it opens.