with my horse I provide her with salt and mineral licks (these have 100ml of Iodine added) and she decides for herself how much she wants, some days she spends the entire day licking, other days she doesn't touch it. I'm giving the chickens a choice between water with Iodine and water without, so far they seem to prefer the Iodine water (2 drops Lugols in 8 litres water). Same for the dogs, they prefer the water with iodine. Animals are pretty smart !!