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Habitat Herd Land Management

How to Increase The Size And Quality of Your Deer

by Dr. James C. Kroll   |  October 2nd, 2017 0

Two of my colleagues recently attended a workshop on supplemental food plots. They came away scratching their heads over the incredible amount of misinformation about nutrition for deer offered by the “expert” putting on the workshop. Since there is a great deal of confusion and false information floating around about what kinds of foods are necessary to increase the size and quality of your deer, I decided to clear up some of the hype surrounding this subject.


Whitetails fall into a category of mammals that showed up sometime just before or around the Pleistocene epoch (2 million years ago). Prior to their appearance, the herbivore community was dominated by groups we call monogastrics, meaning one stomach. For millions of years, mammals — and the dinosaurs before them — carried on a type of adaptive warfare with plants.

The cycle is continuous — plants develop defenses, animals develop solutions. One of these defenses was to produce plants that were less digestible. The grasses fell into this category. They not only placed most of their bodies below ground, but they also became fibrous and difficult to digest. The ruminants became the newest and greatest adaptations on the evolutionary block! They developed three chambers in front of the stomach to deal with breaking down plant fibers and cells like those found in grasses. These are the well-known “stomachs” of ruminants (four in all).

The name “ruminant” comes from the habit these animals have of regurgitating their food, re-chewing it, and then swallowing to start the process all over again. Being a ruminant also had a safety advantage. An individual animal could run out, feed quickly (chewing very little), and then retreat to a safe place to process and digest its food.

Ruminants have some allies in this process. The first chamber is the rumen, which comes from the Latin word for “throat.” The pH of this chamber is almost neutral, and for good reason. The large amount of liquid (about a gallon in deer) is home to a host of microorganisms. Chief among these are bacteria, fungi and ciliate protozoa (single cells with “hairs,” allowing them to move). The more fibrous the diet, the more diverse these organisms become.

Ruminants are classified into several categories based on the type of diet. The most efficient digesters are animals such as cows, classified as “grass-roughage” eaters. At the opposite end of this spectrum are the “concentrate selectors,” to which whitetails belong. They have fewer types of organisms to aid in their digestion. In fact, they may have only a single species of protozoan, but that has not been fully documented.

So, what does this have to do with you? Since deer are very picky eaters and cannot digest fibrous plant materials, they depend heavily on the fresh growing parts of plants, including woody shrubs (browse) and weeds (forbs) to supply protein and needed minerals. They can eat fibrous plant material, but only as a last resort. We see this too often in yarding deer in the Great Lakes states. I have explained this often as the “saltine syndrome.” Ever get hungry in the middle of the night and all you can find to eat in the pantry is a box of saltine crackers? During such times, those crackers are the best things you ever ate, but they’re not necessarily very nutritious! So it is with starving deer. But just because deer eat something does not necessarily mean it’s good for them.

The waste products from the rumen organisms fuel the deer’s activities, plus they provide the basis for producing muscle and other tissues. As the increasingly digestible material passes from the rumen into the next chambers (reticulum, omasum), more and more critical substances and nutrients are extracted. Finally, they reach the true stomach (abomasum), where the microorganisms themselves are killed and digested.

Deer can survive on as little as 6- to 8-percent protein, but they can’t handle this for very long before critical systems in their bodies begin shutting down.


Whitetails are remarkably adept at meeting their metabolic and nutritional needs. For at least 2 million years, they have dealt with annual abundances and shortages. As a consequence, deer thrive in many areas that are nutritionally challenging. In southern Florida, deer get along pretty well on a diet that at best is on the lower end of “desirable.” For example, concentrations of selenium (a vital nutrient to deer) in forage plants in Florida fall way short of what’s required by Northern whitetails.

Too often, however, biologists have asserted that this is evidence there is no need to supplement your herd’s diet. Just because whitetails can survive nutritional challenges does not justify accepting this situation as inevitable.

The nutritional needs of whitetails are related to the time of year and the sex and age of the deer. Millennia ago, deer developed little “tricks” to get by. For example, in winter when plant protein content is very low, they have developed the ability to recycle urea for this purpose. Fawns are born at a time when plants are abundant and highly digestible. Fawns also are weaned when the same situation is prevalent. In South Texas, whitetails wean their fawns just after the hurricane season (August-September), when there is a higher probability of lush plant growth.

How much protein does a deer need? Again, that depends on age and sex. During the first 18 months of life, deer probably have their greatest protein demand. Biologists classify protein demand into three categories, optimum, maintenance and survival. Deer can survive on about 6 to 8 percent protein, but they can’t handle this for very long. They begin to shut down critical systems, their bodies trying to survive long enough to recover when times are better.

Even though whitetails have long been able to thrive in areas that are nutritionally challenging, this does not mean that dietary supplements are unnecessary. Supplemental nutrition can improve the health of almost any herd.

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