Rita, those big turkeys love corn and sunflower seeds. I havn't tried giving them horse feed.
I don't know how such a large bird can find enough to eat in the wild in winter (which is probably why they are all in my yard now). The freezing rain we had recently (two episodes, each laying down one-quarter-inch of ice) must have made it really hard for the turkeys to reach any food on the ground in the surrounding woods and fields. The layer of ice on top of the snow is so resistant, I have to jump up and down on it to break through, and I'm a 170lb woman.