In answer to the request of the chemical composition of antlers,these are true bone and have the same composition viz calcium phosphate with collagen mainly with little bits of other minerals.
To re'M'ington no vast knowledge a liitle more than some and a little less than others
To improve antlers is basically good stockmanship. Your starting point is a triangle.
.....................................Habitat
...............Genetics
...................................Nutrition
You are starting off with a population of deer about which you may know certain facts. this is where your game larder records are indispensable. More info more use. Weights up/down or steady. long term weather conditions,availability of food for previous period. more mouths less food for individual ( stocking density in nutshell). Change of plants etc.
Antler symmetry is entirely determined by genetic makeup. various parts of the country had Roe imports from continental europe and some of these were of mediocre stock, hence low genetic potential. No matter how good nutrition/habitat will hit a plateau after which no improvement.
Years ago Red stags with magnificent racks were moved to the highlands to improve the stock. those that survived reverted to typical highland stock.
Genetic potential hindered by habitat/nutrition
Highland stags moved down south had magnificent antlers.
Genetic potential maximised by habitat/nutrition.
Experts can have pretty good idea form what part of country antlers have originated.
Genetics are there in the population and all you can do is facilitate the best breeding stock. This is where I can explain the science but the art is down to the deer manager/stalker. All the experts tell us to maintain equal parity between the sexes and shoot a higher portion of yearlings equal numbers of males females. More food for the grownups. Shoot too many good heads and you are depressing the male genetic pool, which to a certain extent can be assessed visually by body and antlers. Keep the female population under control or else too many mouths.
Habitat. Is there shelter for the deer after feeding. wide open areas no wind shelter chill factor, more food to keep body temperature less for growth. Anyone been hind culling in highlands will know what I mean.
Nutrition. This is dependent on the soil. Poor soil poor grazing/browsing as the plants are struggling to grow. Hence lower food value. Some soils are deficient in micronutrients and consequently plants deficient. Excess nitrogen fertilizer incredible growth mineral value down. What is needed is a good mixture of browse/grazing with herbs which have these micronutrients including Calcium, phosphorus, selenium,copper magnesium. Protein for growth carbohydrates for energy cellulose for rumenal activity. Deer fed low protein diets experimentally have poor antlers.
First and foremost need a good body before they can grow good antlers. The calcium requirements of red deer stags towards the end of the velvet growth are phenomenal 5 grams a day and if they they can't produce this they from diet chewing bones cast antlers they resorb calcium from their rib bones to make good the deficit.
As you can see from this putting out a few mineral blocks is a waste of time unless you have a proved depressed level of them in the herbage.