Energy Without Nutrients is Just Empty Calories

By: Michael L. Schlegel, PhD, PAS, Dipl. ACAS-Nutrition
Sr. Nutritionist, Wildlife and Small Ruminant Technical Solutions
Purina Animal Nutrition, LLC
Originally appeared in the Winter 2017-18 Issue of the Upper Midwest Cervid Newsletter

Deer need to consume energy to maintain their bodies as is (maintenance energy) and even more energy to grow, reproduce, and produce antlers. In addition to energy, the six required nutrients for deer are protein, fat, carbohydrates (fiber, sugar, starch), minerals, vitamins and water. The key is for deer to receive a balance of energy and nutrients to meet their requirement given their stage of production.

In animal nutrition, the amount of energy in deer feed is calculated as Total Digestible Nutrients (TDN) or as Calories (kilocalories). This dietary energy, be it browse, hay, corn, or pellets, is derived from the feed’s nutrients (protein, fat, and carbohydrates). Fat contains 2.25 times more energy than does protein and carbohydrates. As the animal increases in body size, pregnant with multiple fawns, producing milk for twins or triplets, or growing an exceptional rack of antlers, the amount of dietary energy needed daily increases. The animal will increase its intake to meet its energy needs to a point where the animal cannot consume enough feed (Ammann et al., 1973). This explains why a doe producing milk for four fawns may lose more body condition than the doc lactating for two.

A supplemental feeding program’s goal is to complement the forage with nutrients to allow the deer to reach their potential. While energy is critical, nutrients that are lacking, could hold the deer back from reaching their full potential. As the energy content of feed increases, the animal needs to consume less of the feed to meet its energy needs (Ammann et al., 1973). Therefore, even though the deer is meeting its daily energy requirement, it may not be consuming enough of the critical nutrients to complement its native forage and not able to meet the nutrient requirements to reach its genetic potential for growth, reproduction or antler development.

Additionally, to make a feed that is higher in dietary energy, it requires an increase in protein, fat, or carbohydrates and decreases the room for the other nutrients (minerals and vitamins) that are required for deer to excel. It can also lead to digestive upset. A feed too high in fat can suppress fiber digestion and a feed too high in soluble carbohydrates (sugar and starch) may promote acidosis.

The key is balance. The supplemental feed needs to have an energy content that is needed by the animal and at a rate of consumption that provides the nutrients (protein, minerals and vitamins) to complement the native forage and meet the needs of its stage of production and genetic potential.


Ammann, A.P., R.L. Cowan, C.L. Mothershead, B.R. Baumgardt. 1973. Dry matter and energy intake in relation to digestibility in white-tailed deer. Journal of Wildlife Management 37:195-201.