Mike I think I have an idea of what it is but cant see it super well, so if you dont think this is it post some more pictures or if someone has a better idea let us know. I knew I had seen this type of seed head around before. I beleive it is Armanthus palmeri,aka "Pigweed".Now I doughted it when I first looked it up but there are over 27 different types that it could be, but from a phenotypic standpoint, i belive this is your culprit. But you can get the plant in hand and check it out better than I can from your photo, also i have attached several photos of this specific pig weed that clued me in. The important part that concerns the health of your deer is that yesit can be toxic to livestock, especially if you are in fertile soils. In higher fertility soils this plant builds up toxic levels of nitrates in its leaves, which could cause rumen-health and or pH problems if consumed by your deer, and has even led to death in sheep and cattle - but is rare I think. Still yet hope your deer gets better!