Even antler growth requires protein, as the velvet antler prior to mineralization is made almost entirely of a protein called collagen. Adults have fairly low maintenance requirements, probably about 8-12 percent. Deer can get by with very little protein, or food at all, in the winter. Pregnancy increases requirements slightly, particularly in the first 2 trimesters. In fact, the average fawn at birth contains only 525 grams of protein, and that is produced over a 6-month gestation period.
Lactation places the greatest protein demands on a deer.
The milk of white-tailed deer averages 8.2 percent protein on a wet basis or 36.4 percent on a dry matter basis. Does without adequate protein during lactation will probably not produce poor quality milk, but simply less milk. Does with twins have an even higher protein requirement, probably around 18 percent in the diet. A buck's hardened antlers are about 45 percent protein. We know that body growth occurs before and takes precedence over antler growth, so if protein is in short supply, the deer will have smaller antlers.