From what I've gathered in my studies - Plain salt is craved by most animals, and trace amounts are indeed beneficial to animals by providing Na+, or K+ and Cl- for cell metabolism. In most ranges, the ions provided by salt exist naturally in sufficient quantities to allow for a healthy deer herd. I understand that lactating does can benefit from excess salt (NaCl) in their diets, and is often seen when salt licks are hit especially hard in May and June. Milk quantities are increased as a result of increased water intake and excretion.

That being said, too much salt can indeed be harmful to deer, and other animals. The primary knock on salt is that it causes deer to drink more water (just like it does for a person). Food consumption decreases as much as 20%, because the digestive track is full. On poor ranges, this can be a problem because the needed quantities food required to obtain the correct nutritional balance is cut down. An argument can be made that on good ranges, with excess nutrients, additional salt does not hurt anything. But...my feeling is why would you want to limit the feeding potential of your herd??

My advice...Yes provide good mineral supplements year round for the deer... Increase the Salt content to 30-40% in the fawning months, then go back to a 10-20% salt content for the rest of the year. The salt in your mineral mix is important to bring the deer to your lick - but do not over do it.