I had a couple of wildlife biologists from IDNR chime in on this one. Here is there response: In the Midwest, wild turkeys have access to pretty good nutrition. Supplements are not really necessary. The genetics of the animal limit how quickly growth of these appendages can occur.
The best thing you can do is to properly manage the habitat there. Savannas have both good nesting and brood rearing habitat potential, and they often also support oaks and other trees that have the ‘open grown’ branching tree growth that turkeys like for roosting. Restoration of these types of woodland habitats are one important element of what both the NWTF and IDNR are looking at in Illinois.
Diverse, short grass prairies also serve as good brood rearing areas in my experience (others may have a different view!). Oats have been recommended by some states for use as a turkey food - - turkeys seem to relish them while other birds don’t bother with them as much. Small grain fields such as oats are also good brood rearing areas if not too dense. Oldfield habitat is excellent for brood rearing as long as it is not dominated by tall fescue, which can get a little rank for brood movement. It was once thought turkeys needed big tracts of mature forest to do well, but many of the counties in IL where turkey populations seem to be doing best have scattered woodlots and more edge habitat.
Like deer, wild turkeys in the Midwest are generally on about as high a nutritional level or plane as they can get, with no real need for all of the supplements that get marketed and costs a lot of money. Attracting wild turkeys to a point source for nutrition or supplements also brings up problems with developing a predator target and a point for disease transmission among wild turkeys.
Here are a couple of references:
http://www.dnr.state.oh.us/Portals/9/pdf/pub004.pdf
http://www.oh.nrcs.usda.gov/news/news/turkey_habitat.html
