Beware! Deer Poison

By Matt Harper

 You will not find a bigger proponent for the use of quality mineral/vitamin supplements than the Whitetail Institute. After years of studying, researching and practicing mineral/vitamin supplementation on deer, the Whitetail Institute is a firm believer in the benefits deer hunters and managers can expect.
That is why typically, Whitetail News articles discuss the benefits of supplying quality nutrition to your deer herd. However, there can be a dark side to mineral/vitamin supplementation, if you are using an improperly formulated supplement, which can be harmful. The Whitetail Institute’s position has always been one of focusing on the aspects and benefits of our products and to explain the science and the research that go into developing deer nutritional products. The Whitetail Institute does not sling mud at competitors, and to be honest, that is not the purpose of this article. This article will not single out any particular products or mention names but instead will point out a few things that can make a product ineffective or possibly even dangerous to deer. That may make the Whitetail Institute poor politicians, but in our experience, deer hunters and managers are more interested in what our products can do instead of what our competitors’ products won’t do. But over the past few years, we have seen some products that have formulation aspects that are a cause of some concern, over both ineffectiveness and possible danger. We felt it was important to point out to our readers some of the things that can be done wrong in supplement formulation and may lead to less than desired results.

To begin with, there are several products on the market that may not necessarily be dangerous to a deer, but certainly won’t provide much benefit. The problems found in these products consist of one or more of the following: improper mineral and vitamin ratios, indigestible raw-nutrient sources, improper nutrient level, and a complete lack of a vital nutrient. Many are just glorified salt blocks. Minerals have complicated interactions with each other. Therefore, mineral levels must be formulated so that each mineral works in harmony with the other minerals in the supplement. Ingredient sourcing is also a vital part of deer mineral/ vitamin formulation that is often overlooked by many manufacturers. For example, copper derived from the wrong compound can be virtually useless due to lack of digestibility — copper from copper oxide is very low in digestibility, but copper from copper sulfate is very high in digestibility. As far as improper mineral or vitamin levels and/or complete lack of specific minerals or vitamins in a formulation go, the problem needs little explanation. Without the proper nutrients, a mineral/ vitamin product supplies little benefit at best. Usually, the reason copper oxide is used is because the manufacturers are uninformed and/or because it is cheaper.


Although the errors in formulation we just discussed can decrease the effectiveness of a product, there are other errors in formulation that can actually cause problems. One such problem is mineral toxicity. All minerals can be toxic if consumed at high enough levels. To become toxic, minerals must be consumed at levels that exceed the required amount. Minerals have independent thresholds in which exceeding required levels will show signs of toxicity. With some minerals, there is a high threshold where it can be fed at several times the required amount without becoming toxic. Other minerals have a very small threshold, and toxicity occurs when the mineral level exceeds the requirement by only a small amount. For example, the toxicity threshold for zinc has been found to be fairly high in ruminant animals where zinc toxicity was tested. This means that toxicity only occurs when zinc is formulated at an excessively high level in the diet. That is not say that you should over-feed zinc, as this may cause many other problems not necessarily associated with toxicity. Furthermore, even though zinc has a high toxicity threshold, excessively, high levels can still cause toxicity, especially when these levels are consumed for a long period of time.


At the other end of the scale is selenium. Selenium has a relatively small threshold for toxicity. In other words, toxicity can occur when the requirement is exceeded by a relatively small amount. In fact, the amount of selenium that can be used in a complete diet is government-regulated for many ruminant animals such as cattle, goats and sheep. In most cases, the maximum allowed in a complete diet is 0.3 ppm (milogram/kilogram = milograms of selenium per kilogram of total diet). Therefore, it is important when formulating a mineral/vitamin supplement to not have a selenium level that, when consumed at a typical amount, will cause the overall diet to have a selenium level exceeding 0.3 milograms of selenium per kilogram of total diet. In the side bar of this article, I have described an example using a hypothetical supplement containing 60 ppm of selenium, consumed at 2 ounces per deer per day, with the deer eating a total of 10 pounds (4.5 kilograms) of diet per day. In this example, we find that the resulting selenium consumption would be 0.75 ppm or milograms per kilogram of total diet. This is a little over double the regulated amount for most ruminants (for more details, see sidebar).

Will this supplement cause toxicity in deer? Technically, a selenium toxicity level in deer has not been established. However one thing is for sure: in our example, the supplement, based on a deer eating 4.5 kilograms of total diet, including 2 ounces of the mineral/vitamin supplement, will certainly cause the selenium in the diet to exceed the regulated amount of 0.3 ppm (milogram/kilogram). Keep in mind that this regulation was put in place due to the small threshold between selenium requirement and toxicity. It is important to note that the regulatory amount of 0.3 ppm is used for domesticated ruminants and is also commonly accepted by most deer nutritionists as the maximum level to be used in diets. Disregard for the safety factor imposed by the regulatory number in product formulation, if not considered dangerous, should at least be considered reckless.

One factor we did not consider in our example is additional selenium coming from natural forages. Certain soils have a high selenium content making the forage have a higher than normal level of selenium. If you combine a high selenium supplement with forages already high in selenium, toxicity concerns become even greater. Yet another factor to consider is that selenium has been shown to build up or be stored in body tissues. Prolonged over-consumption of selenium may also place a deer at risk of toxicity. In other words, problems may not occur right away, but over time, symptoms may begin to show up. In some cases, however, symptoms may not be very apparent, which is the case for animals suffering from chronic toxicity. In cases where acute toxicity occurs, symptoms can include emaciation, loss of hair, soreness and sloughing of hooves, anemia, blindness, staggering, paralysis and death. Again, we need to understand that selenium is a vital trace mineral in a deer supplement. However, selenium formulation should be based on the best information we have available in terms of maximum amounts of selenium that should be supplemented in a diet. As I mentioned before, disregard for the safety factors built in by commonly accepted maximum selenium levels is risky and a disservice to deer hunters and managers.


Another major problem I have seen is the use of ingredients not normally used in animal supplements. These ingredients are not typically used because of the side effects and problems they may cause. One example is an ingredient called sodium carbonate. This is not to be confused with sodium bicarbonate, which is often used in animal feeds as a source of sodium and a buffering agent. Sodium carbonate (sodium ash), rather, is normally found in the chemical industry serving a multitude of various functions but is commonly used in detergents as a water-softening agent.

Without getting into a lot of chemical jargon, sodium carbonate is fairly volatile in terms of chemical reactions, which is why it lends itself well to water softening. However, sodium carbonate is not normally used in the feed industry because of the undesired effects it may have on animals. Primarily, the biggest problem with sodium carbonate is that it has a very high pH, around 12. This high alkaline level may cause damage to the nasal passages, sinuses and the respiratory system. In fact, the MSDS sheet for sodium carbonate warns of these very side effects.

In comparison, sodium bicarbonate has a pH of about 8, which is why it is favored in animal diets. The problems that can occur with extended use of sodium carbonate are obvious; nasal passage, sinus and respiratory damage. The reason sodium carbonate is used is because it is an attractant but mainly because it is very cheap. It is cheaper than sodium bicarbonate and even cheaper then regular salt in most cases. The price, and most likely the manufacturers being uninformed, are the likely reasons why these products are even on the market.

Now that I have sufficiently scared you away from using deer mineral/vitamin supplements, I would like to bring up something I mentioned at the beginning of this article. Mineral/vitamin supplementation can dramatically improve the quality of your deer herd. Increased antler growth and larger body weights are only of few of the benefits you can see. However, some of the products I have seen on the market do not use a sound nutritional basis in their formulation. At the very least, these products will be ineffective and in some cases may even be detrimental.

The safest way to go is to use products designed by companies that have professional nutrition experts working for them. The Whitetail Institute mineral/vitamin supplements and nutritional supplements, such as 30-06 Mineral products and the Cutting Edge line of products, were developed by deer nutrition professionals with years of education and experience.

As a member of the research staff at the Whitetail Institute, I can assure you that our products are formulated by experts who know deer nutrition and product formulation. So the next time you are browsing the selection of deer mineral/vitamin supplements, keep the things we talked about in mind. There are products out there that can benefit your deer herd, but if you are not careful, you may choose a product that will cause more harm than good. n

Selenium Toxicity >>>>>

To help explain selenium formulation, let’s use the following example. Lets say a deer is going to eat 10 pounds of food per day. This is equivalent to 4.5 kilograms. This means that the maximum amount of selenium the deer should consume in that day should be 1.35 milograms (0.3 milogram X 4.5 kilograms of diet = 1.35 total milograms of selenium).Now lets say that you are using a mineral/vitamin supplement that contains 60 ppm of selenium. Using a consumption of 2 ounces per head per day (typical consumption of free choice minerals), a supplement containing 60 ppm (milogram/kilogram) of selenium would supply a total of 3.4 milograms of selenium (2 ounces = 0.125 pounds and 60 ppm = 27.27 milogram/ pound, 0.125 X 27.27 = 3.4 milograms of selenium). So in this example,we have exceeded the daily regulated amount by slightly more than 2 milograms. Another way of looking at is by comparing the regulated milogram/kilogram of selenium to actual milogram/ kilogram of selenium the deer is consuming. In the example, we have been looking at a deer eating 4.5 kilograms of total diet including 2 ounces of a supplement containing 60 ppm (milogram/kilogram) of selenium. In this calculation we would find that the deer would be consuming 0.75 milogram of selenium per kilogram of diet, which again is more than double the regulated amount of 0.3 milogram/kilogram. (Total selenium consumed, 3.4, divided by the total diet (4.5), 3.4/4.5 = 0.75 milogram/kilogram or ppm.)