Mojo, There has been numerous studies done over the years and to date not one has shown any benefit (other than providing a source of salt) from mineral supplements.
Here is an article by QDMA.'s leading biologist Brian Murphy, If anyone would write an article that supported using mineral supplements it would be him since his employer (QDMA) generates alot of advertising $$$$
from companies that produce mineral supplements on their TV show and their Magazine.
"""""""""""""""""""""""""""""""""""""A classic study on the mineral needs of deer was conducted at Penn State University in the 1950s. In this study, researchers did detect a difference in yearling buck antler development between supplemented and unsupplemented groups. However, these herds were fed a nutritionally deficient diet below what most whitetails would have access to in the wild. Furthermore, when the same deer were examined the following year as 2.5 year olds, no differences were detected between the two groups.
In a similar study conducted at Auburn University, researchers tried to detect differences in body and antler size between an unsupplemented and supplemented group. This study differed from the Penn State study in that both herds were fed a nutritionally complete diet. In addition, one group was provided a commercial mineral supplement. Over a four year period the researchers were unable to detect any differences between the two deer herds.
Without question deer need minerals, and they will readily use mineral licks. But why do they use these licks and why is their use restricted primarily to the spring and summer? Many hunters believe that it is simply because bucks need the minerals for antler growth and does for raising fawns during these months. However, several studies have shown that while deer readily use mineral licks high in salt, they rarely, if ever, use pure mineral supplements. If deer were lacking minerals, why wouldn't they use the pure mineral supplement even if salt wasn't present? No one can say for sure, but it's probably because most minerals by themselves are bitter.
Could the use of salt/mineral mixes simply be due to an increased need for salt? According to research, yes. During the spring and summer, deer operate at a sodium deficiency due to the high potassium and water content of the forage. This interferes with efficient sodium conversion in the body and increases the need for sodium. This makes deer actively seek out concentrated sources of sodium such as natural or man?made licks. Almost all soils more than 25/50 miles from a seacoast are low in sodium. Therefore, in these areas, salt may be just as necessary as calcium and phosphorus to whitetails during the spring and summer."""""""""""""""""""""'""""""""""""""""""""
Here is what CJ said in an article on this subject, who by the way is not only a well respected biologist but an editor of Bowhunter mag.
""""""""""""""""""""""""""Over the last several decades, biologists at Universities across the country have researched the effects mineral supplementation has on a bucks' rack. In most cases, they put deer in two pens. In one pen, the deer were feed their regular diet. In the other, the deer ate a mineral in addition to their regular diet. After a few years in most studies, researchers did not see a noticeable difference. Many biologists bring up the research every time a hunter brings up minerals. C.J. Winand, a biologist from Maryland, believes that minerals are hocus pocus. "All of the data available today says that mineral supplementation doesn't have a lasting impact on antler size. Research is being done regularly and until I see a study that shows that minerals help deer grow larger racks, I will continue to believe what I believe," Winand explained."""""""""""""""""""""""""""""""""""""""" "