The Chemistry of the Growth of Deer Antlers

Introduction

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I chose to research the growth of deer antlers. This decision was easily made due to my interest in anatomy, biology, and hunting. This knowledge will help me better understand why antlers grow the way they do, and it will also help the deer population with the understanding of what comes into play in knowing whether a deer is healthy or not, and which animal is an ethical shot.


Composition of ...

  • Encased in velvet-

    • 20% dry matter, 80% crude protein, 22% calcium, and 11% phosphorus

  • Polished antlers-

    • 60% dry matter, 40% crude protein, 25-35% calcium, and 19% phosphorus

Main Chemicals, Compounds, Components

Protein Hormone- Prolactin

  • Prolactin also is known as the Luteotropic hormone. In humans this protein is known for enabling mammals to produce milk. However this protein has over 300 separate actions in vertebrates. The protein is secreted from the pituitary gland, and this action is regulated by endocrine neurons in the hypothalamus. The protein is similar to the growth hormone. The molecule has three disulfide bonds, causing folds in the structure.

Testosterone

  • Testosterone is a steroid hormone found in vertebrates. This hormone mainly deals with reproduction and sexual characteristics (antlers). The hormone like many other steroid hormones is developed from cholesterol by biosynthesis.


Chemistry's Role

All of the compounds of the deer antlers are not man-made. They all occur in the deer’s body naturally, very similar to our own.

Background Research

- Antlers are found on the family of Cervidae. These bone growths are found on male deer, sometimes females grow antlers, but this is normally a deformity. The tissue that makes up the antlers is one of the fastest growing tissues, even faster than some cancer cells. It takes about 10 months for the deer to grow a full rack. The process begins in March or April, this is when the days lengthen. At this point of time a gland called the pineal alerts the pituitary gland.The pituitary gland has the protein hormone, prolactin in the anterior lobe, the production of this protein hormone increases under more “exposure” to daylight. Also, with the increased production of prolactin the body begins producing more testosterone. Testosterone is the main driving force for the production, when testosterone decrease the antlers are shed (winter months, January/February), also this includes a decrease in muscle mass and the need to deposit more fat for energy.

A common assumption about the growth of antlers is that they grow from the base like fingernails, but it is actually the opposite. The antlers start as a soft cartilage that is continuously  built on top of, like a layered cake. Some scientists say that the growth can be split into two stages, the formation of the pedicle and then the initial growth of the antler on top. The pedicle is the base of the antler, and it is encased in a covering called antlerogenic periosteum. The periosteum begins to differentiate (specialize) due to the increase of testosterone in the blood. The periosteum cells multiply and grow, and undergo mineralization (deposits of calcium and phosphorus). Mineralization ends up in another process called ossification, turning soft tissue (cartilage) to bone. On top of the pedicle (blastema) and under the periosteum is mesenchymal tissue, it is under constant mitosis. Mesenchymal tissue turns into the cartilage and is then ossified into the trabecular bone (specifically endochondral ossification). The periosteum membrane is ossified into the cortical bone (specifically intramembranous ossification). Meanwhile this entire process is going on underneath hair, called velvet. Velvet carries oxygen and minerals to the bone through the superficial temporal artery.

Once the breeding season (rutt) approaches even more testosterone is increased and it causes a restriction of blood flow to the velvet. With the lack of blood flow to the velvet it begins to die and shed off. In the beginning the antler is white bone, but due to thrashing and rubbing on bushes and trees it stains the antlers anywhere from brown to grey.

For a long time people thought that once the velvet was shed that there was no “food” supply for the antlers so they become “dead bone”. But this is not true, the antler actually has a vascular system running through it, keeping it moist. Also, the mineralization process is thought to not end until a few weeks before the antler itself is cast away. Just because the antler is considered a “living bone” does not mean that it has nerves running through it anymore. WIth the shedding of the velvet the nerve supply from the trigeminal nerve die, so a deer with a broken antler did not feel the break.

Testosterone allows the body to keep the antlers, but when they supply drops so does the ability to keep them. Basically the deer’s body sends osteoclasts to break down the bone, this process is known as osteoclastic resorption.


Resources

http://www.suwanneeriverranch.com/WTinfoIantlers.htm

-Antlers are made of true bone, shed every year, also addresses velvet.

https://en.wikipedia.org/wiki/Antler

-Addresses general ideas about the antler including human usage, and sexual selection

http://outdoorchannel.com/article.aspx?id=3620

-Chemical composition of hardened antlers, nutrition, and growth rates

http://extension.missouri.edu/p/G9486

-Purposes of antlers, how they grow, deformities, and injuries.

https://muledeer.org/hunting/mule-deer-facts/

-Focuses on mule deer behavior and touches on differences between whitetail and mule deer antlers

http://www.suwanneeriverranch.com/WTinfoL.htm

-Discusses differences in genetics, terrain, behavior of the 3 different species

http://www.sportsmanschoicefeeds.com/scf/en/learning-center/nutrition/all-about-the-rack/index.jsp

-More specific into the antler growth

http://www.nyantler-outdoors.com/deer-antler-growth.html

-Discusses more about deer antler growth, also has some growth rate data and other things

http://www.wildlifeonline.me.uk/questions_answers_deer.html

-Questions and answers about dee, including growth and development

https://buckmasters.com/resources/YBO/antlers-and-glands

-  Discusses glands in deer during antler growth

https://en.wikipedia.org/wiki/Prolactin

-General information on prolactin, including effects on body, mainly discusses humans

https://en.wikipedia.org/wiki/Testosterone

-General information about testosterone


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