September 22, 2010
We ended Part 1last month by asking this question: How much protein does a deer need? Fawns and yearlings need as much as 24 percent, but generally do well with 16 to 17 percent. Once grown, bucks seem to need less protein than any other segments of the herd. I have observed bucks produce quality antlers with as little as 10 percent protein (15 to 17 percent is optimum).
Does, on the other hand, need a great deal more, especially during pregnancy and nursing (16 to 24 percent). There also are short-term critical times, such as right after weaning, when does attempt to recoup body mass. Bucks have two stress periods: 1) just after antler casting, and 2) during mineralization and velvet stripping.
So how is protein measured? The above values are percentages of total intake. If a deer eats about 10 pounds of forage per day, that means a 16 percent protein demand converts to 1.6 pounds of protein per day. When we send in forage samples to our research laboratory for analysis, two different protein levels are measured: 1) dry weight, and 2) "as fed." These are important differences.
The first is measured after the sample is thoroughly dried, while the second is calculated as what is present when the animal swallows it. We classify plants as either "nutrient dense" or "nutrient diffuse." In the former, a single mouthful contains a great deal of nutrition, while for the latter, the volume is the same but the amount of nutrition is lower.
ENERGY AND FAT IN DEER
More often than not, energy is the limiting factor for whitetails. Energy permits almost every body function. Digestible forages allow the rumen organisms to produce more volatile fatty acids, sugars, etc., to power the deer's body. However, foods can be too digestible, creating some very serious problems. For example, where legal, corn grain is commonly used as bait for deer. But too much corn can speed up production of the waste products of rumen organisms.
Normally, these waste products are useful, but too many can change the rumen environment. Remember, in Part 1 last month I noted that the rumen must remain at neutral pH (7). A buildup of acidity kills the rumen organisms, leaving the deer without a means of acquiring nutrients. It starves to death in the presence of plenty!
Deer are obligatory fat depositors, meaning they deposit fat at certain times of the year, no matter what the level of nutrition may be. This is why hunters frequently misinterpret a fat deer harvested during the hunting season as deer being in good shape the rest of the year. Biologists conduct "health checks" in many areas during late summer and late winter, the two worst times for deer.
Deer generally have a very different type of fat than cattle. White fat found in deer has a very low melting point, allowing deer to mobilize this stored energy quickly. The yellow fat common to cattle is much more difficult to metabolize. This is one of the many reasons why venison is so much better for you!
Deer do not have a gall bladder. This is important, since they only need about 3 percent fat in their diet. Bile serves to emulsify fat in the diet. Since deer do not seek out fatty foods, this process is not necessary. Deer are on a "reverse" Atkins diet. They seek out, rather than shun, high carbohydrate foods. Too often, managers try to provide fat supplements with disastrous results. At best, a deer given a high fat diet will excrete oil through its skin. If you rub your hand down the back of such an animal, your hand will become greasy!
MINERALS IN DEER -- A LITTLE GOES A LONG WAY!
Finally, we turn to minerals. Minerals are classified into two categories: micronutrients and macro-nutrients. The prefixes do not come from the size of the elements, but rather from the amounts used by an animal. Micronutrients are used in very small quantities and can be toxic if the levels exceed a maximum. Macronutrients such as sodium are used in high proportions, especially during certain times of the year.
There is an exhaustive list of critical nutrients, too many to discuss here. However, the most important macronutrients are calcium, phosphorus, sodium, potassium and magnesium. The amounts needed vary, but the ratio often is critical. For example, the ratio of calcium to phosphorus in the diet will affect utilization of these important nutrients. In most cases, a 1-to-1 or 1-to-2 level is needed. Our studies on East Texas browse plants commonly show ratios exceeding 1-to-50! Micronutrients include copper, zinc, selenium, manganese and boron.
Small amounts of nutrients in forage are concentrated and stored at very high levels. This is also true for milk and antlers. Phosphorus and calcium requirements for nursing does and bucks growing antlers are remarkably similar. Some scientists even have hypothesized that the weight of mature antlers and the skeletons of fawns are highly correlated.
We have measured milk production as high as 72 ounces per day for some of our research does. Although there are no studies to support my hypothesis (yet), I think the genes associated with nursing and those with antler growth are similar or even the same.
There have been several studies analyzing the nutrient content of antlers. In every case, the components are remarkably similar. In order of abundance, these components are: calcium, phosphorus, magnesium, sodium, selenium, zinc and copper. To put the concentration of nutrients into perspective, a section of antler will yield about 20 percent calcium and 10 percent phosphorus, while a reasonable browse plant will have 0.45 percent and 0.28 percent of those minerals, respectively.
Our research on the micronutrient content of velvet antlers and other studies indicated a much higher concentration of this micronutrient in the growing tips of antler points. This also was true for copper and zinc.
Micronutrients are important to metabolism and other body functions. Selenium has been proven to be a catalyst for activities such as sperm production and cell division, both critical activities for deer. Zinc has been demonstrated to be important for immune response (antioxidants and antibodies), and copper (as with zinc) influences cell growth and immune response. Being micronutrients, too much of any of these can have serious side effects on your deer.
Here is a good "bad" example. When it was learned by deer farmers that selenium was important to antler growth, many of these folks concocted prepared feeds with very high levels of this micronutrient. As a consequence, we received calls for help from folks who had given their bucks heavy metal poisoning!
The big question we arrive at in this second installment is this: How do you develop a plan that provides optimum nutrition to the deer on your property that is both effective and practical? In Part 3 next July, I hope to clear away the fog created by misinformation about what works and what does not.