Question: “We are interested in whitetail deer management so as to improve the deer hunting on our property located in Pennsylvania. The subject of feeding protein to deer gets mentioned a lot, and we understand that better deer nutrition leads to more fawns and bigger antlers in bucks. We already do some habitat manipulation to help the deer and we have lots of browse plants. However, we are unsure of whitetail deer protein requirements. Do you think protein is a limiting factor and would our deer would benefit from supplemental foods with high levels of protein?”
Answer: First, understand that most whitetail deer get their nutrition from plants found in their environment. So good job on your current situation. It sounds like your habitat management activities are producing a lot of high quality browse plants for deer. These browse plants are high in protein. Feeding deer, protein or otherwise, gets a lot of attention. The biggest reason is because it is the easiest thing a hunter can do.
Believe it or not, protein is not as Limiting as many deer managers think. That being said, it’s like a beef-loving hunter choosing between a t-bone and a ribeye. Both high-quality cuts will provide the protein levels that their body needs, but one is typically preferred. The same thing can be said of deer. On well-managed lands, quality plants will be available that deer can eat. On properties that have good natural foods and provide protein pellets, for example, deer have a choice. Some will go for the pellets, some will prefer the native stuff. Many will use both.
To understand protein metabolism and requirements in whitetail deer, it is important to keep in mind that whitetail are ruminants. Much of the protein that deer use does not get put directly to work. In fact, microbes in the whitetail’s rumen use much of the dietary protein for their own growth and reproduction. This sounds like a bad for the deer, but it’s not. The important thing to remember is that microbes are continually passing out of the deer’s rumen, which are then digested by the deer.
The conversion of plant protein to microbial protein benefits whitetail deer. Deer do need protein, but they really need are the building blocks of protein—amino acids—to survive and thrive. Whitetail deer can actually make their own proteins if they have the necessary amino acids. Also, many amino acids can be manufactured from other amino acids by the deer.
After reading the above paragraph, it would sound like deer do not need to consume much protein at all since they can create their own from amino acids, but deer can not create all the different types of amino acids that they need. The “must-have” amino acids that deer are required to have in their diet are called essential amino acids.
People and other non-ruminant animals require 10 essential amino acids in their diet. Without them, their growth is poor. Ruminants, on the other hand, do not have requirements for essential amino acids because the rumen microbes convert plant protein to microbial protein, which the deer then digests. Amino acids in the microbial protein closely match the whitetail deer’s requirements. So, one reason why deer are not as limited by protein as many people believe is that microbes help ensure the amino acid composition of the diet matches that needed by the deer.
My recommendation to you would be to maintain the deer population on your Pennsylvania property within the carrying capacity of the habitat. As long as they are not overcrowded they should fill their deer protein requirements from the browse, forbs and mast found there. Improving whitetail deer is about age, genetics and nutrition. The most important factor on many properties is simply allowing deer to reach their genetic potential. They will never do that if they do not have good nutrition and are not allowed to grow old. Manage for good habitat, proper deer density and age and the deer hunting on your property will improve. Feed them if you really want to.