You would think we would know a great deal about the mineral requirements of deer. Unfortunately, due to the difficulties of working with wild animals, and the lack of adequate facilities and large numbers of deer for this work, our knowledge of the mineral requirements of deer is sketchy at best.
The total mineral content of a deer’s body is only about 5 percent. The major minerals we are concerned about are calcium and phosphorus. These are obviously needed for bone and antler growth, but also for milk production, blood clotting, muscle contraction, and general metabolism.
Hardened deer antlers are about 22 percent calcium and 11 percent phosphorus. The many studies of the mineral requirements for antler growth have yielded conflicting results, partly because of small numbers of deer involved, and because of the sometimes overriding influence of genetics on antler growth. Early studies indicated that 0.09% Calcium (Ca) and 0.27% Phosphorus (P) were the minimum required for antler growth. A later study showed a diet of 0.64 percent Ca and 0.56% P necessary for antler growth. Pennsylvania State later found that 0.20 percent P was adequate. At Mississippi State we found P levels as low as 0.14-0.29 percent were adequate. Michigan State has found that 0.45 percent P is optimal for fawns.
One of the reasons these mineral levels seem so low, and may be so variable, is the fact that bucks can store minerals in their skeletons, and transfer them to the antlers when needed. In fact, during antler mineralization, male deer undergo an “osteoporosis,” or removal of minerals from their bones, similar to that which happens in elderly women. The difference is that after the antlers harden, the minerals lost from the bones are replaced from the diet.
Unfortunately, we know even less about the deer’s possible requirements for other macro- or micro-minerals. Deer may need sodium (Na), as they will often use salt licks. We don’t know if this is because they are lacking this mineral, or perhaps it just tastes good. In some areas of the country selenium deficiencies, which lead to a condition known as white muscle disease, have been suspected. We really have little information on the need for other trace elements.