The process usually ends two to three weeks before the autumn equinox in September. A buck sports its hardened antlers through January or February, often using them to spar and fight for dominance with other bucks. Once antlers cast, their pedicle is an open wound that bleeds a short time before scabbing.
Antlers begin growing soon after the wound fully heels. Hormone levels, including testosterone, vary by buck and affect their antler growth timeline. Because antlers change from soft cartilage beneath velvet to hard bone, their proteins, minerals and elements change, too. The nutrients a buck consumes affects its antler composition while each section grows.
Generally, antler tips have more protein and minerals than the bases. Soils with poor mineral content, make it harder for recovery, and in a lot of cases where soil quality is low, supplemental feeds help to make mobilization a little more efficient. As stated above in the section outlining factors for growth, the only way to really dive into the role of genetics is to control the environment and nutrition of two or more genetically different deer.
MSU did just that in this study. Researchers took pregnant does from three distinct regions of Mississippi that represent different genetics, the Delta a lot of nutrients and genetically large deer , Thin Loess less agriculture and slightly smaller deer , and LCP genetically smaller deer with poor nutrition.
The plan was to feed the male fawns from the does the exact same high-nutrition diet and see how they grew in captivity. If the smaller deer remained small and the genetically bigger deer remained large, then it could be said that genetics, regardless of nutrition, can hold back the growth of body size and antler size.
If the smaller deer grew as large as the others, then nutrition would surpass genetics as the most important factor for growth. While body size in the first generation remained somewhat consistent to their respective regions, antler size did increase.
However, the study took a really interesting turn when the bucks fathered another generation of deer in captivity. The second generation was much bigger than the first, and there was a huge jump in both antler growth and body size. This was especially the case for the genetically smaller deer. This phenomenon can be explained through something called epigenetics. While the DNA sequence in deer remains the same, environmental conditions cause small changes, and over generations, those changes will alter the expression of the genes.
From the MSU study :. This is how animals naturally adapt to their environment and what we see in the quality of our deer is representative of that generational adaptation. Because of the incredible amount of energy it takes to grow antlers, they will remain smaller as well. So, in a way, yes, genetics do play a big part in antler growth, but the idea that genetics are set in stone to produce small deer is not exactly true.
Manage the land accordingly, and in a few generations, smaller cervids could grow exponentially bigger. Big antlers, in a way, are an indication of good health in the herd.
The rate of growth is ultimately influenced by nutrition, which includes protein, energy and minerals.
French et al. There also seems to be an age difference, with younger bucks requiring more protein. Older bucks may be able to achieve good antler growth with as little as 10 percent, but the overall recommendation is at least 16 percent. This is why warm-season plots and supplemental feed are so important to promoting antler growth. Next comes energy. All life depends on maintaining a proper energy balance - taking in more than you expend.
Fortunately, antler growth occurs at a time when energy is most available and least expended. In addition to the direct effect of predation, the mere presence of predators increases energy demands as deer must be more vigilant and expend more energy to avoid them. You should also keep other disturbance like human intrusion to a minimum.
Last, but certainly not least, is minerals, and this is where things really get interesting. What we do know is that because they make up a significant proportion of the final product, calcium and phosphorous are key elements. Other trace minerals like manganese, copper, zinc and selenium likely also play some role, though to what extent is unknown. We also know that selenium is present in higher concentrations in velvet and the growing antler tips.
This is why soil is so important, and why you should test your soil and follow the recommendations. Plants take up minerals and other nutrients from the soil. The richer the soil, the richer the plants.
Deer then eat those plants and convert their nutrients into useable form for various bodily functions, not the least of which is growing a crown of antlers. However, the path from soil to antler is indirect. The process of converting these elements into bone is called mineralization. And even when minerals are abundant in the environment, much of what goes into antlers is mobilized from other parts of the skeleton.
During peak antler growth periods, bucks may experience a 20 percent decrease in mineral content in other bones. This, in part, explains why there is typically a big jump in antler growth between age three and four. By age four a buck is mature. His skeleton has stopped growing and no longer requires as much mineral nutrients.
Antlers are still a luxury, but any surplus minerals not needed for normal body function can now go directly to antler growth. This is also why age is such an important factor in antler growth. Maximum antler size is usually achieved between age five and seven. After that a buck reaches senescence and a period of gradual deterioration. The process of mineralization occurs largely toward the end of the annual antler growth cycle.
Photoperiodism - in this case shortening day length - again plays a role, stimulating the pituitary gland to increase secretions of testosterone. This triggers the mineralization process as soft antler tissue is converted to bone when minerals are deposited within the matrix of cartilage and blood vessels.
A once diffuse vascular system solidifies, cutting off the supply of blood and minerals. The antlers and their velvet covering literally die. Velvet sloughs off completely within about 12 hours, leaving the dead bone of the completed rack behind. Exceptions do occur and are usually the result of injury, often to the testes, or sometimes the result of retarded testicular growth. Deer antlers take a lot of energy to grow.
The antlers are bony, and like bones are made mostly out of calcium. Deer do not consume much calcium with their vegetarian diet, and the calcium in the antlers is grown just like the calcium in the bones, produced by chemical reactions in their bodies. This takes up a large amount of available nutrients and energy, and only the healthiest deer can grow large antlers.
Even the largest antlers grow from small nubs to full size in three to four months, making them one of the fastest-growing types of tissue. They begin as small bony growths at the top of the head, and are covered with a layer of skin and hair known as velvet. This velvet keeps the antlers protected while they are fragile. When antlers have reached a larger size and slow down or stop growing, the blood vessels that keep the velvet growing shut down around the base of the antlers.
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