Wild deer are herbivores, which means they eat mostly plant-based substances. Fruits, nuts, plants and grasses are most common in a wild deer's diet. Wild fawns are dependent on their mother's milk.
To feed a wild deer, it is important to provide a diet that is similar to what is available in the wild. If the deer is a fawn, goats milk can be substituted for mother's milk. Utah Division of Wildlife Resources warns against unnecessary feeding of wild deer, especially in the winter time. While it may seem that the deer needs supplemental nutrition, the wrong type of food certain times of the year can actually harm a wild deer.